Profiles of Drug Substances, Excipients and Related Methodology vol 19, Volume 19 (Analytical Profiles of Drug Substances, Excipients, and Related Methodology)

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Analytical Profiles of Drug Substances Volume 19 Edited by

Klaus Florey The Squibb Institute for Medical Research New Brunswick, New Jersey

Contributing Editors

Abdullah A. Al-Badr School of Pharmacy, King Saud University Riyadh, Saudi Arabia

Timothy J. Wozniak Lilly Research Laboratories, Indianapolis, Indiana

ACADEMIC PRESS, INC. Harcourt Brace Jovanovich, Publishers SanDiego New York Boston London Sydney Tokyo Toronto

EDITORIAL BOARD

Abdullah A. Al-Badr Gerald S. Brenner Glenn A. Brewer Harry Brittain Klaus Florey George A. Foxier

Lee T. Gmdy Berry J. Kline G. William Martin David J. Mazzo Timothy J. Wozniak

Academic Press Rapid Manuscript Reproduction

This book is printed on acid-free paper. @ COPYRIGHT 0 1990 BY ACADEMIC PRESS,INC. All Rights Resewed. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical. including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher.

ACADEMIC PRESS, INC. San Diego, California 92101

United Kingdom Edition published by ACADEMIC PRESS LIMITED 24-28 Oval Road, London NW17DX

LIBRARY OF CONGRESS CATALOG CARD NUMBER: 89-659072 International Standard Serial Number: 0099-5428

ISBN 0-12-260819-4 (alk. paper)

PRWIED IN THE UNITED STATBS OF AMERICA 90 91 92 93

10 9 8 1 6 5 4

3 2 1

AFFILIATIONS OF EDITORS AND CONTRIBUTORS

Mohummud A. Abounussif, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia Christiunuh M . Adeyeye, School of Pharmacy, Duquesne University, Pittsburgh, Pennsylvania 15282 Sutinder Ahuju, Pharmaceutical Division, Ciba-Geigy, Suffem, New York 10901 Abdulluh A. Al-Budr, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia Khulid A. Al-Rushood, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia Fuhud J. Al-Shummury, College of Applied Medical Sciences, King Saud University, Riyadh 11451, Saudi Arabia Hunun N . Alkaysi, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid, Jordan Tawfiq A. Argut, Faculty of Pharmacy, University of Jordan, Amman, Jordan J.Ashmun, Pharmaceutical Division, Ciba-Geigy, Suffem, New York 10901 Adnun A. Budwun, The Jordanian Pharmaceutical Manufacturing Co., Ltd., P. 0. Box 94, Naor, Jordan Ronald J.Bopp, L a y ResearchLaboratories,L a y Corporate Center, MC769, Indianapolis, Indiana 46285 A u k Bult, Faculty of Pharmacy, State University of Uuecht, 3511 GH Utrecht, The Netherlands Robert A. Carr, Faculty of Pharmacy, University of Alberta,Edmonton T6G 2N8, Canada

vii

Viii


James E . Carter, Janssen Research Foundation, 40 Kingsbridge Road, Piscataway, New Jersey 08855-3998 JitYDohnul,Research Institute for Phannacy and Biochemistry,Kourimska 17, 13060,Prague 3, Czechoslovakia Robert T.Foster, Faculty of Pharmacy, University of Alberta,EdmontonT6G 2N8, Canada MahmoudM. A. Hussan, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia Joost J. M. Holthis, EmCetus B. V., Paasheuvelweg30,1105 BJ Amsterdam, The Netherlands Ivan Jeftnek,Research Institute for Pharmacy and Biochemistry, Kourimska 17,13060, Prague 3, Czechoslovakia Vijay K . Kupoor, Departmentof Pharmaceutical Sciences,Panjab University, Chandigarh 160014,India J. Juntim Kettenes-van den Busch,Faculty of Pharmacy, University of Utrecht, 3511 GH Utrecht, The Netherlands Pui-Kai Li, School of Pharmacy, Duquesne University, Pittsburgh, Pennsylvania 15282 AbdefG. Mekkawi, Riyadh Health Institute, Ministry of Health, Riyadh 11451, Saudi Arabia MohammadSaleemMian, Collegeof Pharmacy, King Saud University,Riyadh 11451, Saudi Arabia Neelofur Abdul Aziz Mian, College of Applied Medical Sciences, King Saud University, Riyadh 11451, Saudi Arabia Farid J. Muhfudi, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia Linu Bahouth Uwais,The Jordanian PharmaceuticalManufacturingCo., Ltd., P. 0. Box 94, Naor, Jordan Vdcfav Rejholec, Research Institute for Pharmacy and Biochemistry, Kourimska 17,13060, Prague 3, Czechoslovakia Donald S.Rzkley,Lilly Research Laboratories,Lilly CorporateCenter, MC769, Indianapolis, Indiana 46285 Mutaz Sheikh Salem, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid, Jordan Jos Van Rompuy, Janssen Pharmaceutica, Beerse, Belgium Zva Vanturovd,Research Institute for Pharmacy and Biochemistry, Kourimska 17,13060, Prague 3, Czechoslovakia Terry D.Wilson, Sterling-WinthropResearch Institute, Columbia Turnpike, Rensselaer, New York 12144


ix

TimothyJ . Wuzniuk,Lilly ResearchLaboratories, Lilly Corporate Center, MC769, Indianapolis, Indiana 46285 Muhammad Uppal Zubair, Center for University Women Studies, King Saud University,Riyadh 11451, Saudi Arabia

PREFACE

Although the official compendia define a drug substance as to identity, purity, strength,and quality, they normally do not provide other physical or chemical data, nor do they list methods of synthesisor pathways of physical or biological degradation and metabolism. Such information is scatteredthrough the scientificliteratureand the files of pharmaceuticallaboratories. I perceived a need to supplement the official compendial standards of drug substanceswith a comprehensivereview of such information,and eighteen years ago the first volume of Analytical Profiles of Drug Substances was published. That we have been able to publish one volume per year is a tribute to the diligence of the editors to solicit articlesand even more so to the enthusiasticresponse of our authors, an international group associated with pharmaceutical f i i s , academic institutions, and compendialauthorities. I would like to express my sincere gratitudeto them for making this venture possible. Over the years, we have had queriesconcerningour publication policy. Our goal is to cover all drug substances of medial value, and therefore, we have welcomed any articles of interest to an individual contributor. We also have endeavored to solicit profiles of the most useful and used medicines,but many in this category still need to be profiled. Klaus Florey

xi

ACEBUTOLOL

Robert T . F o s t e r Robert A . Carr

Faculty of Pharmacy & Pharmaceutical Sciences University o f A1 berta Edmonton, A1 berta, CANADA T6G 2N8

Description 1 . 1 Nomenclature 1 . 2 Formula 1 . 3 Molecular Weight 1 . 4 Appearance, Color and Odor 2 . Synthesis 3 . Physical Properties 3 . 1 Infrared Spectra 3 . 2 NMR Spectra 3 . 3 Mass Spectra 3 . 4 Ultraviolet Spectra 3 . 5 Melting Point 3 . 6 Dissociation Constant 3 . 7 Partition Coefficient 3 . 8 Color Tests 3 . 9 Solubility 4 . Methods of Analysis 4 . 1 Colorimetric Analysis 4 . 2 Radioimmunoassay 4 . 3 Chromatographic Analysis 5 . Pharmacokinetics 5 . 1 Absorption 5 . 2 Distribution 5 . 3 Metabolism 5 . 4 Excretion References Acknowledgements 1.

ANALYTICAL PROF'ILES OF DRUG SUBSTANCES VOLUME 19

I

Copyright 0 1990 by Academrc Press, Inc. All nghts of reprduclion in any form reserved.

ROBERT T. FOSTER AND ROBERT A. CARR

L

1. DESCRIPTION 1.1

Nomenclature

1.1.1

Chemical Names

N- [3-Acetyl-4-[ 2-hydroxy-3- [ (l-methyl ethyl )amino] propoxylphenyl] butanarnide (1,2) ; 3’-acetyl-4’-[2-hydroxy-3- (isopropylamino)propoxy]butyranilide; 1-(2-acety1-4-n-butyramidophenoxy)2-hydroxy-3-isopropyl aminopropane; 5’ -butyramido-2’- (2-hydroxy-3-isopropyl aminopropoxy) acetophenone. IL-l7803A, M & B 17803A (1). Chemical abstracts registry no.: 37517-30-9; 34381-68-5 (hydrochloride). 1.1.2

Nonpropri etary Name

Acebutolol (1) 1.1.3

Proprietary Name

Acetanol, Acecor, Diasectral, Neptall, Monitan, Prent, Sectral , Secradex (1,2). 1.2

Formula

1.2.1

Emp rica

C18H28N204; Hydrochloride, Ci~H2gClN204 1.2.2

Structural

Figure 1 depicts the structure o f acebutolol and its major metabol ites, acetolol and di acetol . 1.3 Molecular Weight

336.43 (base) ; 372.89 (hydrochloride)

3

ACEBUTOLOL

OCH2CH(OH)CH2NHCH(CH& I *

NHR FIGURE 1.

Structure of acebutolol and two metabol i tes, acetolol and diacetolol . Acebutolol , R = CO(CH ) CH - Diacetolol , R = COCH ; Acetoyof, H. The asterisk denotes the chiral center.

a’=

(*y

Appearance, Color and Odor fine white, or slightly off-white crystalline, non-hygroscopic, practically odorless powder (3). 1.4

A

2. SYNTHESIS The synthesis of acebutolol has been described as follows (2): After preparation of 5’-butyramido-2’- (2,3epoxypropoxy)acetophenone, the compound was heated together with isopropylamine and ethanol and allowed t o reflux for 4 hours (for details on preparation of 5’-butyramido-2‘-(2,3-epoxypropoxy)acetophenone, see ref. 2). The reaction mixture was concentrated and dissolved in hydrochloric acid. This solution was extracted with ethyl acetate and the organic layer was discarded. Using 2 N sodium hydroxide, the acidic solution was basified and extracted with chloroform. The chloroform extracts were concentrated, yielding an oil. The oil was crystallized from a mixture of


4

ethanol and diethyl ether to give the final product, 5'-butyramido-2'-(2-hydroxy-3-isopropylaminopropoxy)acetophenone (acebutolol )

.

A general scheme depicting the synthesis of acebutolol has

also been reported, and is shown in Figure 2 (4).

3 , PHYSICAL PROPERTIES Infrared Spectra The infrared spectrum o f acebutolol i s presented in Figure 3. The spectrum was obtained from a KBr disk using a Nicolet 7199 Fourier Transform infrared pectrometer. Diagnostic peaks were observ d at 3420 cm-f (alcohol, 0-H stretch, H-bonded) ; 33501cm-f (secondary amine, N-H strytch); 3000-2850 cm - (a1 kane, C-H siretch); 1700 cm- (ketone, C=O stretch); and 1660 cm- (amide, C=O stretch). The peaks are presented in Table I. The infrared spectrum o f acebutolol HC1 has previously been reported which id ntified peaks at 1665, 1245, 1525, 1495, 1217 and 1285 cm-' (5).

3.1

3.2

NMR Spectra The 300 MHz proton NMR spectrum o f acebutolol in CDC13 is described in Table 11. The spectrum was obtained on a Bruker AM-300 FT NMR spectrometer. Instrumental settings were: time domain (data points) , 16K; aquisition time, 1.819 sec.; spectral width, 4504.51; pulse width, 25"; receiver gain, 200; line broadening, 0.200. The spectrum is shown in Figure 4. The D20 exchange NMR spectrum o f acebutolol is shown in Figure 5. As expected, the exchangeable protons (-OH, -NH-, -CONH) are absent, whereas a single, intermediate peak is present at 4.836. 3.3

Mass Spectra

AEI MS9 (Manchester, U.K.) instrument equipped with a fast atom bombardment source (Figure 6). The medium was glycerol and the sample was introduced by means of a direct insertion probe. Instrument settings were: mass range, 93-676; total scans in run, 4; sampling rate, 128; signal level threshold, 30; minimum peak width, 7; scan rate (sec/dec), 10.0. A mass spectrum was obtained on a

0

/ \

COCH3 I

NHCOCH2CH2CH3

I

NHCOCH2CH2CH3

NHCOCH2CH2CH3

FIGURE 2. Synthetic Pathway for Acebutolol (from ref. 4).

FIGURE 3 .

Infrared spectrum of Acebutolol . KBr pel 1 et. Instrument: Nicolet 7199 Fourier Transform Infrared Spectrometer.

ACEBUTOLOL

7

I. I .R. Spectrum o f Acebutolol . KBr pellet. (Instrument: Nicolet 7199 Fourier Transform I . R . )

TABLE

Wavenumber (cm-l)

Relative Intensitya m, broad

3424 3385 2965 293 1 2880 1692 1654 1612 1593 1545 1498 1467 1410 1358 1299 1270 1237 1219 1189 1146 1024 910 880 820 590 538 3s

=

S

m W W S S W W S

S

W W W

S

m

S S

m W

W W

W W W W

strong; m

=

medium; w

=

weak.


8

TABLE 11.

300 MHz Proton NMR o f Acebutolol i n CDC13.

OCHzCH(OH)CH2NHCH(CH& I

NHCOCH2CH2CH3

Chemical S h i f t ( r e 1 t o TMS)

.

Number o f Protons

Assignment

t d sextet broad 2.35 t 2.67 s i n g l e t 2.8 m

3 6 2 2 2 3 3

CH CH -

4.08 6.96 7.34 7.63 7.95

3 1 1

-0CH2 - , - CHOH -Ha - CONH -Hb - HC

1.02 1.11 1.76 2.05

d broad, s i n g l e t d q

1 1

- C i ( C i 12 CH CH$H -Nd-, -06 -CH CH2CONH

-cot.

-CH Na-cH~!cH~;~

I

I

9

FIGURE 4.

I

E

7

I

6

5 PPfl

I

. I

I

1

3

Proton NMR Spectrum o f Acebutolol . Instrument: Bruker AM-300 FT NMR spectrometer

2

1

e

0

I

9

E

7

6

5

9

3

2

1

rpn

FIGURE 5.

Proton NMR Spectrum o f Acebutolol . D20 exchange. Instrument: Bruker AM-300 FT NMR spectrometer.

loo

60 70

50

30 20

1

337

i 1

116

100

FIGURE 6.

200

300

Positive Ion FAB Mass Spectrum o f Acebutolol. Instrument: AEI, MS9. Medium, glycerol.


12

Acebutolol gave a prominent peak (base peak) [MH'] of m/z 337 in the positive ion detection mode. Fragments were detected at m/z (% re1 ative abundance) : 98(8), 100( lo), 116(19), 151(5), 338(26) and 339(6). The fragmentation pattern for the positive ion mode has been presented in Figure 7. A previously reported mass spectrum identified peaks at m/z 72, 43, 30, 56, 151, 221, 41 and 98 (5), although the mass spectrometry conditions were not 1 isted. Using electron-impact mass spectrometry, with ionization energy of 70 eV (Hewlett-Packard MSD Series 5970 A), acebutolol reportedly gave prominent fragments of m/z 108, 136, 151, 193 and 235. In this previous report, the authors concluded that acebutolol had been hydrolysed to an aminophenol derivative under the stated conditions (6). 3.4

U1 travi ol et Spectrum

The ultraviolet spectrum of acebutolol in chl oroform obtained using a PU8700 series UV/VIS spectrophotometer (Philips, England) is depicted in Figure 8. This qua1 itative spectrum depicts maximal wavelengths at 241.6 and 328.5 nm under the stated conditions. The spectra, as re orted by others (5), were: 1) aqueous acid 234 nm ( A q l = 655, unknown reliability) and 320 nm (A' = 75 unknown reliability), and in 2) methanol, 245 nm ( A l l = 866, mean value based on several reported figures, all within d o % of the mean), and 328 nm. 3.5

Melting Point

Acebutolol melts within the range of 119-123 " C (1, 5). The hydrochloride salt has a melting point of 1411144 " C (5). 3.6

Dissociation Constant The pka of acebutolol is 9.4 (5).

3.7

Partition Coefficient

The partition coefficients of acebutolol in n-octanol/phosphate buffer, incubated for 1 hour, were: 0.17 (20 "C, pH 7.0); 0.35 (37 "C, pH 7.0); and 0.68

+

- CH,CHZCH-C=O

15f NHCOCH2CHZCH3 MH:&~

FIGURE 7.

337

Fragmentation P a t t e r n o f Acebutolol ; P o s i t i v e I o n FA6 Mass Spectrum.

+

+

+

+

+

+

+

+

+

+

c

FIGURE 8 .

U1 traviolet Spectrum of Acebutolol in Chloroform. Instrument: PU8700 series scanning UV/VIS spectrophotometer.

ACEBUTOLOL

(37 "C, pH 7.4) ( 7 ) . Others have r e p o r t e d d i s t r i b u t i o n c o e f f i c i e n t s o f 0.974 and 1.008 a f t e r 2 and 6 hours, r e s p e c t i v e l y , i n n-octanol/phosphate b u f f e r (pH 7.4, 37 " C ) (8) * 3.8

Color Tests

The t e s t s and r e s u l t a n t c o l o r s have been r e p o r t e d (5) as: m e t h a n o l i c potassium hydroxide, y e l l o w ; N e s s l e r ' s reagent, orange (slow); s u l p h u r i c a c i d , y e l l o w . 3.9

Solubility

A c e b u t o l o l has a r e l a t i v e l y l o w l i p i d s o l u b i l i t y ( 9 ) . A c e b u t o l o l h y d r o c h l o r i d e has r e p o r t e d s o l u b i l i t i e s o f 200 mg/mL i n water and 70 mg/mL i n ethanol a t room temperature ( 3 ) . The h y d r o c h l o r i d e s a l t i s f r e e l y s o l u b l e i n w a t e r .

4. 4.1

METHODS OF ANALYSIS Colorimetric Analysis

A c e b u t o l o l has been analyzed u t i l i z i n g a c o l o r i m e t r i c assay (10). B r i e f l y , t h i s method i s as f o l l o w s : A c e b u t o l o l was e x t r a c t e d from plasma a f t e r a d d i t i o n o f g l y c i n e b u f f e r (pH 10) and e t h y l a c e t a t e . The o r g a n i c l a y e r was e x t r a c t e d t w i c e w i t h 3 M s u l f u r i c a c i d and t h e two a c i d e x t r a c t s were combined and heated a t 99 " C f o r 2 hours. T h i s l a t t e r s t e p r e s u l t e d i n t h e h y d r o l y s i s o f t h e butyramide group which, t h e r e f o r e , generated t h e aromatic amine. Water was added t o t h i s s o l u t i o n and t h e m i x t u r e was c o o l e d t o 4 "C. A f t e r c o o l i n g , a 1% (w/v) s o l u t i o n of sodium n i t r i t e was added, f o l l o w e d by t h e a d d i t i o n o f ammonium sulphamate (5% w/v). T h i s s o l u t i o n was shaken a t i n t e r v a l s o v e r 15 minutes. A f i n a l c o l o r l e s s s o l u t i o n o f n a p h t h y l e t h y l e n e d i a m i n e d i h y d r o c h l o r i d e (1%w/v) was added t o t h e m i x t u r e and a l l o w e d t o stand a t room temperature f o r 2 hours. D u r i n g t h i s time, f u l l c o l o r development o f t h e m i x t u r e occurred. Absorbance was determined a t 565 nm u s i n g a scanning spectrophotometer o v e r t h e range o f 400-700 nm.

15


16

The reported sensitivity of the assay (0.1 ug/mL) is insufficient for routine clinical monitoring of acebutolol after administration of conventional doses. Furthermore, the assay was non-specific, as both acebutolol and its major metabolite, diacetolol, were detected but not separated from one another. 4.2

Radi oimmunoassay

Antisera against acebutolol was produced in rabbits immunized with drug conjugated with bovine serum (11). Radioactive tracer (tritiated acebutolol) was produced by May and Baker (specific activity = 9.6 Ci/mmole). The reported sensitivity was 2.97 x lo-' mol/L of acebutolol. 4.3

Chromatographic Analysis

4.3.1

Thin-Layer

Various systems have been used to detect acebutolol (12,13). The thin-layer chromatographic analyses have been summarized in Table 111. 4.3.2

Gas

Gas chromatography has been utilized for the analysis of acebutolol (6,14,15). These methods may lack convenience, as multiple extraction steps contribute to somewhat laborious sample preparation. When applied to analysis of acebutolol in urine, the reported gas chromatography methods are essentially initial screening procedures (qualitative, as opposed t o quantitative) based on the following conditions:

1.

2.

Hewlett-Packard Series 5790 A gas chromatograph with H-P capillary column (12 m x 0.2 mm I.D., cross-linked methylsilicone), 0.33 um film thickness. The temperature was programmed from 100 to 310 "C at 30 "C/min. The injection port temperature was 270 "C and the carrier gas was helium at a flow-rate of 2 mL/min. Mass spectrometry was used for detection (6). Carlo Erba HRGC 5160 MEGA gas chromatograph with a

ACEBUTOLOL

17

TABLE 111. Rf Values of Acebutolol under Various Thin-Layer Chromatographic Conditions. P1 ate 1.

Sil ica Gel 60 F254 (Merck)

2.

Sil ica Gel 60 F254 (Merck)

Sol vent System

Rf Value Ref.

Ethyl acetate: methanol : 30% ammonia (85:10:5)

41-

12

Cycl ohexane : to1 uene: d i ethy 1 ami ne

02

12

0-

12

63

12

0.0

13

0.73

13

(65:25:10) 3.

Sil ica Gel 60 F254 (Merck) 4.

Silica Gel 60 F254 (Merck)

5.

Silica Gel, 0.22 mm (Polygram Sil N-HR) 6.

Silica Gel, 0.22 mm (Polygram Sil N-HR)

Ethyl acetate: chloroform (50 :50)

Acetone dipped in 0.1 M pot ass i um hydroxide methanol ic solution Ethyl acetate: methanol (40:5)

Ethyl acetate: methanol : ammon i a (sp.gr. 0.88) (40: 5: 5)

-Corrected value (see ref. 1 2 ) .

18


J & W Durabond 1 capillary column (30 m x 0.25 mm I.D.), film thickness of 25 urn. Temperature was programmed as 1 minute isothermal at 90 "C, and then 40 "C/min to 260 "C. This was followed by a final isothermal period for 15 minutes at 260 "C. Mass spectrometry was used for detection (14). The analysis o f acebutolol in plasma has been reported using a gas chromatographic technique (15). Unlike the methods (above) reported for urine, this method can be used for determination of acebutolol in a quantitative sense. Briefly, the method (which offered sensitivity t o approximately 25 ng for acebutolol), was reported using a Hewlett-Packard 5710A series gas chromatograph with a nickel 63 electron capture detector. The column was glass (6 foot, 2 mm I.D.), packed with 3% Dexsil 410 on 100-120 mesh gas-chrom Q. The carrier gas was 5% methane in argon set at a flow o f 40 mL/min. The injection port was 250 "C, oven was 275 "C, and the detector was set at 300 "C (15). 4.3.3

High- Performance Liquid

a. Nonstereospecific. There have been numerous reported methods for the analysis of acebutolol using high-performance 1 iquid chromatography (16-22). These methods typically involve reversed-phase chromatography, isocratic flow, and ultraviolet detection. Table IV summarizes the chromatographic conditions used for detection of acebutolol . b. Stereospecific. The enantiomers o f acebutolol have been separated and quantified in biological samples using high-performance 1 iquid chromatography (23-25). The methods are based on pre-column derivatization with a homochiral reagent, and are summarized as follows: 1.

2.

Reversed-phase columns (C18) utilizing a mobile phase consisting of methano1:water (62:38) at a flow rate of 1.2 mL/min. The chiral derivatizing reagent was (S)-(-)-l-phenylethyl isocyanate. The di astereoi somers were detected using fl uorescence detection at 209 and 320 nm, excitation and emission, respectively. The sensitivity of the assay for acebutolol enantiomers was not reported (23) * Reversed-phase columns (ODS2) utilizing a mobile phase consisting of water:methanol :triethylamine

ACEBUTOLOL

TABLE I V . Assays.

1.

19

Chromatographic C o n d i t i o n s o f Reported HPLC

Column

Mobi 1e Phase

Detector

Ref.

c

Methanol : 0.0005 M HC1 i n 0.05 M NaCl (35: 65) (1.2 mL/min)

UV, 254 nm (fixed) UV, 220 nm (variable)

16

16-w 250 x 4.6 mm (I.D.) 2.

Spheri s o r b ODS 5-um 250 x 3.9 mm (I.D.)

Acetonitrile: 0 . 1 M phosphate b u f f e r (pH 3.3): water (55:6:39) (1 mL/min)

UV, 240 nm

17

3.

Varian MicroPack MCH-10 250 x 2.0 mm (I.D.)

0.01 M dodecyl sodium s u l f a t e i n water a d j u s t e d t o pH 3.5 w i t h glacial acetic a c i d (Pump A), and same as Pump A, w i t h a d d i t i o n o f methanol (50%) (Pump B) (0.67 mL/mi n)

UV, 240 nm

18

4.

Radial -Pak

Methanol :water (75:25) (1.8 mL/min)

UV, 248 nm

19

Phase I Methanol :0.02 M sodium a c e t a t e b u f f e r (pH 5.8) (80:20) ( 1 . 5 mL/min)

Amperometric, 20 operated a t t0.7 V versus saturated calomel reference electrode

ioiUIm (I .D.)

5.

LiChrosorb

21

;-Ymrn (I.D.)

(continued)


20

TABLE I V .

(continued)

Column

Mobi 1e Phase

Detector

Ref.

Phase I 1 Acetonitrile: 0.02 M sodium acetate buffer (pH 5.8) (80:20) (1.5 mL/min) Phase I 1 1 Ethanol :0.02 M sodium acetate buffer (pH 5.8): d i c h l oromethane (90: 5: 5) (1 .O mL/min) 6.

LiChrosorb S i 7-um 150 x 4.0 mm (I.D.)

Phosphate b u f f e r (pH 2.2) w i t h increasing organic modifier (1 mL/min)

UV, 270 nm

21

7.

Spheri s o r b ODS 5-um 250 x 4 . 6 mm

6% o f 0.1 M phosphate b u f f e r (pH 4.0) and 55% aceton i t r il e (1.0 mL/min)

UV, 243 nm

22

(I.D.)

ACEBUTOLOL

3.

5.

(50:50:0.05) at a flow rate of 1.2 mL/min. The chiral derivatizing reagent was (R)-(+)-1-phenylethyl isocyanate. Fluorescence detection was set at 238 and 450 nm for excitation and emission, respectively. The reported sensitivity was approximately 0.05 ug/mL for each enantiomer (24). Normal-phase columns (silica) utilizing a mobile phase consisting o f hexane:chloroform:methanol (63:35:2) at a flow rate of 2.0 mL/min. The chiral derivatizing reagent was S-(t)-1- (1-naphthyl)ethyl isocyanate. Fluorescence detection was set at 220 and 389 nm, excitation and emission, respectively. The reported sensitivity was 10 ng/mL for each enantiomer (25).

PHARMACOKINETICS

5.1

Absorption

Acebutolol is absorbed rapidly, resulting in peak plasma concentrations being achieved within 2-4 hours (26-28). The presence of food or alcohol does not significantly alter the absorption profile of acebutolol (29). A1 though approximately 90% of an oral dose is absorbed (30), the extent of systemic availability is only between 35% and 45% after administration of drug v i a this route (9). This finding has been explained by the extensive first-pass (hepatic) removal of acebutolol, which contributes to overall drug clearance. 5.2

Distribution

Acebutolol is weakly bound to plasma proteins (11-19%) The volume of distribution at steady-state has been reported as between 1.0 to 1.2 L/kg after intravenous dosing (32). After oral dosing, the reported volume of distribution of acebutolol enantiomers was 11.3k3.5 and 9.2k2.6 L/kg for R- and S-acebutolol, respectively (26). Although these two studies reported different volumes of distribution, the differences were likely attributable, in part, to: 1) measures of enantiomer versus total ( R plus S-acebutolol) concentrations, and 2) differing methods (31).

21


22

of calculating volume terms, where the latter report on acebutolol enantiomers did not factor the amount of drug reaching the systemic circulation after oral dosing. Following intravenous administration of acebutolol , brain concentrations were similar to atenolol, and less than those reported for propranolol , metoprolol , and oxprenolol (9). These findings were consistent with the drug’s physicochemical properties (i.e., low protein binding, 1 ow 1 i pophil ici ty) . 5.3

Metabol i sm

After oral administration of acebutolol to man, the drug is extensively metabolized upon first-pass through the liver. The main metabolite that is formed v i a this first-pass has been identified in man as diacetolol, which has a potency similar to that of acebutolol (27,33-35). Prior to formation of this major metabolite, however, the butyramido group of acebutolol is initially hydrolyzed to form acetolol , a primary amine (36). Subsequently, acetolol undergoes N-acetyl ation to form the diacetolol metabolite (9). It has been suggested that this first-pass formation of diacetolol is stereoselective for the R-(+)-enantiomer (26). The structures o f acebutolol, acetolol and diacetolol have been shown previously (see Figure 1). The N-acetylation o f acetolol has been reported to be independent of acetylator status (34). In elderly subjects, plasma concentrations of acebutolol and diacetolol are significantly higher than in young subjects, which may be a function of either a decreased first-pass metabolism and/or decreased volume of distribution (37). 5.4

Excretion

Acebutolol has a terminal elimination half-1 ife ranging from approximately 3 hours (28) to 8 hours (37,38). Renal excretion of acebutolol and di acetolol together accounted for approximately 25% to 45% of an orally administered dose of acebutolol , whereas after intravenous dosing renal excretion of acebutolol accounted for 40% to 60% of the administered dose (9). In a study of patients with reduced renal function, urinary excretion of both acebutolol and diacetolol was diminished (38). However, the terminal half-1 ife of elimination o f acebutolol was unchanged in renal insufficiency. On the contrary, the terminal

ACEBUTOLOL

h a l f - l i f e o f d i a c e t o l o l was prolonged i n p a t i e n t s w i t h reduced r e n a l f u n c t i o n ( 3 5 ) . Consequently, i t was assumed t h a t a non-renal compensatory mechanism o f e l i m i n a t i o n o f a c e b u t o l o l e x i s t e d . I t has f u r t h e r been suggested t h a t non-renal c l e a r a n c e may, i n p a r t , c o n s i s t o f b i l i a r y and/or i n t e s t i n a l e x c r e t i o n o f a c e b u t o l o l ( 3 9 , 4 0 ) . More r e c e n t l y , i t was determined t h a t t h e non-renal c l e a r a n c e o f acebutolol i s stereoselective (26,41). A c e b u t o l o l i s e x c r e t e d i n t o b r e a s t m i l k , as plasma l e v e l s o f t h e d r u g were d e t e c t e d i n newborn i n f a n t s b o r n t o h y p e r t e n s i v e women t r e a t e d w i t h a c e b u t o l o l ( 4 2 ) . A c e b u t o l o l i s e x c r e t e d i n t o s a l i v a and c e r e b r o s p i n a l f l u i d , a1 though c o n c e n t r a t i o n s o f a c e b u t o l o l i n c e r e b r o s p i n a l f l u i d a r e much l o w e r t h a n those found i n plasma ( 4 3 ) .

ACKNOWLEDGEMENTS The a u t h o r s a r e i n d e b t e d t o Drs. F.M. Pasutto, R.T. C o u t t s , E.E. Knaus and M. Hussain f o r t h e i r c o n t r i b u t i o n s t o t h e p r o f i1e.

23

24


REFERENCES 1. M. Windholz, e d i t o r , The Merck Index, 1 1 t h e d i t i o n , Rahway, NJ, Merck & Co., I n c . (1989), 4. 2. M. S i t t i g , Pharmaceutical Manufacturing Encyclopedia, 2nd e d i t i o n , Park Ridge, NJ, Noyes Pub1 i c a t i o n s (1988), 5. 3. American Hospital Formulary Service: Drug Information, Bethesda, MD, American S o c i e t y o f H o s p i t a l Pharmacists (1989), 773. 4. B. B a s i l , J.R. Clark, E.C.J. Coffee, R. Jordan, A.H. Loveless, D.L. Pain and K.R.H. Wooldridge, J. Med. Chem., 19, 399 (1976). 5. A.C. M o f f a t , s e n i o r c o n s u l t i n g e d i t o r , Clarke's Isolation and Identification of Drugs, 2nd e d i t i o n , London, England, The Pharmaceutical Press (1986), 309. 6. H. Maurer and K. P f l e g e r , J. Chromatogr., 382, 147 (1986). 7. P.B. Woods and M.L. Robinson, J. Pharm. Pharmacol., 33, 172 (1980). 8. M. Neider, W. S t r o s s e r and J. Kapper, Arzneim. Forsch., 37, 549 (1987). 9. G DeBono, C.M. Kaye, E. Roland and A.J.H. Summers, Am. Heart J., 109, 1211 (1985). 10. M.F. C u t h b e r t and R.F. C o l l i n s , Br. J. Clin. Pharmacol., 2, 49 (1975). 11. B. Gourmel, J. F i e t , R.F. C o l l i n s , J.M. V i l l e t t e and C Dreux, Clin. Chim. Acta., 108, 229 (1980). 12. G. Musumarra, G. S c a r l a t a and G. Cirma, J. Chromatogr., 350, 151, (1985). 13. D.B. Jack, S. Dean and M.J. Kendall, J. Chromatogr., 187, 277 (1980). 14. M. Leloux, E.G. DeJong and R.A.A. Maes, J. Chromatogr., 488, 357 (1989). 15. P.J. M e f f i n , S.R. Harapat and C. H a r r i s o n , Res. Comm. Chem. Path. Pharmacol., 15, 31 (1976). 16. B.R. P a t e l , J.J. Kirschbaum and R.B. Poet, J. Pharm. Sci., 70, 336 (1981). 17. T.W. Guentert, G.M. Wientjes, R.A. Upton, D.L. Combs and S. Riegelman, J. Chromatogr., 163, 373 (1979). 18. P.J. M e f f i n , S.R. Harapat, Y-G. Yee and D.C. H a r r i s o n , J. Chromatogr., 138, 183 (1977). 19. A.C. Mehta and R.T. C a l v e r t , J. Chromatogr., 276, 208 (1983). 20. P. Leroy and A. N i c o l a s , J. Chromatogr., 317, 513 (1984).

ACEBUTOLOL

21. S-0. Jansson, I . Andersson and M-L. Johansson, J. Chromatogr., 245, 45 (1982). 22. J.N. Buskin, R.A. Upton, R. Matthew Jones and R.L. W i 11iams, J. Chromatogr., 230, 438 (1982). 23. P-H. Hsyu and K.M. Giacomini, J. Pharm. S c i . , 75, 601 (1986). 24. A.A. Gulaid, G.W. Houghton and A.R. Boobis, J. Chromatogr., 318, 393 (1985). 25. M. P i q u e t t e - M i l l e r , R.T. Foster, F.M. P a s u t t o and F. Jamali, J. Chromatogr., 526, 129 (1990). 26. M. P i q u e t t e - M i l l e r , R.T. F o s t e r , C.T. Kappagoda and F. Jamali, J . Pharm. S c i . , accepted (1990). 27. A.A. Gulaid, I . M . James, C.M. Kaye, O.R.W. Lewellen, E. Roberts, M. Sankey, J. Smith, R. Templeton and R.J. Thomas, Biopharm. Drug D i s p . , 2, 103, (1981). 28. C.M. Kaye, C.R. Kumana, M. Leighton, J. Hamer and P. Turner, C l i n . Pharmacol. T h e r . , 19, 416 (1976). 29. R. Zaman, M.R. W i l k i n s , M.J. Kendall and D.B. Jack, Biopharm. Drug D i s p . , 5, 91 (1984). 30. R. G a b r i e l , C.M. Kaye and M.G. Sankey, J. Pharm. Pharmacol., 33, 386 (1980). 31. T.J. Coombs, C.J. Coulson and V.J. Smith, B r . J. C l i n . Pharmaco7., 9, 395 (1980). 32. P.J. M e f f i n , R.A. Winkle, F.A. P e t e r s and D.C. H a r r i s o n , C l i n . Pharmacol. T h e r . , 22, 557 (1977). 33. B. F l o u v a t , A . ROUX, N.P. Chau, M. V i a l l e t , X . Andre-Fouet, R. Woehrle and J. Gregoire, E u r . J. C l i n . Pharmacol., 19, 287 (1981). 34. A. Gulaid, I . M . James, C.M. Kaye, O.R.W. Lewellen, E. Roberts, M. Sankey, J. Smith, R. Templeton and R.J. Thomas, B r . J. C l i n . Pharmacol., 5, 261 (1978). 35. W. K i r c h , H. K o h l e r , G. Berggren and W . Braun, C 7 i n . Nephrology, 18, 88 (1982). 36. R. Zaman, D.B. Jack, M.R. W i l k i n s and M.J. K e n d a l l , Biopharm. Drug D i s p . , 6, 131 (1985). 37. A. ROUX, J.F. Henry, Y. Fouache, N.P. Chau, M.P. Hervy, F. F o r e t t e , J.P. Bourdarias and B. F l o u v a t , G e r o n t o l o g y , 29, 202 (1983). 38. A. ROUX, P. Aubert, J. Guedon, and B. F l o u v a t , E u r . J. C l i n . Pharmacol., 17, 339 (1980 39. T.J. Coombs, C.J. Coulson and V.J. Smith, B r . J. C l i n . Pharmacol., 9, 395 (1980). Oh, J. Pharm. Pharmacol., 28, 40. C.M. Kaye and V.M.S. 449 (1976).

25

26


41. R.T. Foster, M. Piquette-Miller, C.T. Kappagoda and F. Jarnal i , Pharm. R e s . , submitted (1990). 42. G. Bianchette, C. Dubruc, P. Vert, M.J. Boutroy and P.L. Morselli, C l i n . Pharmacol. T h e r . , 29, 233 (1981). 43. R. Zaman, D.B. Jack and M.J. Kendall, Br. J. Clin. Pharmacol., 12, 427 (1981).

ANALYTICAL PROFILE OF AMOBARBITAL

Neelofur Abdul Aziz Mian Fahad J. A-Shammary Mohammad Saleem Mian*

Clinical Laboratories Department, College of Applied Medical Sciences, King Saud University, P.O. Box 10219, Riyadh-11433, Saudi Arabia.

*Pharmaceutical Chemistry Department, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh-11451, Saudi Arabia.

ANALYTICAL PROFILES OF DRUG SUBSTANCES VOLUME 19

21

Copynght 0 1990 by Academic Press. Inc. All rights of repmduction HI any form reserved.

NEEMFUR ABDUL AZIZ MIAN, ETAL.

28

Contents

1.

Description 1.1 1.2

1.3 1.4 1.5

2.

Nomenclature 1.1.1 Chemical Names 1.1.2 Generic Names Formulae 1.2.1 Empirical 1.2.2 Structural 1.2.3 CAS Registry Number Molecular Weight Elemental Composition Appearance, Color, Odour and Taste.

Physical Properties 2.1 2.2 2.3 2.4 2.5 2.6 2.7

Melting Range Solubility pH

Hygroscopicity Dissociation Constant X-Ray Powder Diffraction Spectral Properties

3.

Synthesis

4.

Metabolism

5.

Toxicity

6.

Uses

7.

Cautions

29

AMOBARBITAL

8.

Methods of Analysis 8.1 8.2 8.3 8.4 8.5

9.

10.

Elemental Analysis Identification Titrimetric Spectrophotometric 8.4.1 U V Absorbtion Spectroscopy 8.4.2 Infrared Spectroscopy Chromatographic Methods 8.5.1. Paper Chromatography 8.5.2 Column Chromatography 8.5.3 Gas Chromatography 8.5.4 Thin-Layer Chromatography 8.5.5 High Performance Liquid Chromatography

Acknowledgements References

NEELOFUR ABDUL AZIZ MIAN, ETAL.

30

1.

Description Nomenclature 1.1.1

Chemical Names

5-Ethyl-5-(3-methylbutyl)-2,4,6-(lH,3H,5H) pyrimidinetrione. (1) 5-Ethyl-5-isopenthylbarbituric acid (1,2,3,4,5). 5-Ethyl-5-isoamylbarbituric acid (1). 2,4,6 (lH, 3H, 5H)-pyrimidinetrione, 5-ethyl-5(3-methylbutyl). (4) 5-Isoamyl-ðylbarbituric acid. Acide isopentyl-5-ethylbarbiturique ( 6 ) . 1.1.2

Generic Names

Amylobarbitone, Amal, Amasust, Amystal, Amylobarb, Amytal, Amobarbitalum, Amobarbital, Amobarbitale, Amsal, Amycal, Amydorm, Amytal, Barbamyl, Barbamil, Dormytal, Etamyl, Euntoctal, Isoamitil, Isobec, Isonal, Isomytal, Mylodorm, Neur.Amy1, Placidel, Pentymal, Pentymalum, Sednotic, Stadadorm, Somnal, Sedantite, Sedante, Trasital. 1.2

Formulae 1.2.1

Empirical Ci 1Hi 8 Nz 0 3

1. 2 .2

Structural

H

0

31

AMOBARBITAL

1.2.3

CAS Registry Number 57-43-2

1.3

Molecular Weight 226.27

1.4

Elemental Composition C 58.39%,

1.5

H 8.02%,

N 12.38%,

0 21.21%.

Appearance. Color, Odour and Taste

white odourless crystalline, powder with a slightly bitter taste. (2)

A

2.

Physical Properties 2.1

Melting BanRe 156-158". (1)

2.2

Solubility

One gm dissolves in 1300 ml water, in 5 ml alcohol, in 17 ml chloroform, in 6 ml ether. Freely soluble in benzene, soluble in alkaline solutions. Insoluble in petroleum ether, aliphatic hydrocarbons (1). It dissolves in aq. solutions of alkali hydroxides and carbonates. ( 3 )

A saturated aqueous solution is acidic to litmus paper

(1) saturated solution in HzO has a pH of about 5.6 (2).

2.4

lfpgroscopicitn

It is hygroscopic (6) it absorbs significant amounts of moisture at 25', relative humidities upto about 90%. (5)


32

2.5

Dissociation Constant

The drug has a pKa (Dissociation constant) 8.0 (25"). 2.6

X-Bas Powder Diffraction

of Ambarbital Sod.

The X-ray diffraction pattern of amobarbital sod. was determined by a Philips full automated X-ray diffraction spectrogoniometer equipped with PW 1730/10 generator (8). Radiation was provided by a copper target (Cu anode 2000 w, y = 1.5480 A ) and high intensity x-ray tube operated at 40 KV and 35 MA. The monochromator was a curved single crystal one (PW 1752/00). Divergance slit and the receiving slit were 1 and 0.1' respectively. The scanning speed of the goniometer (PW 1050/81) used was 0.02-20 per second. The instrument is combined with Philips PM 8210 printing recorder with both analogue recorder and digital printer. The goniometer was aligned using silicon sample before use. The X-ray pattern of amobarbital sod. is presented in Fig. (1). The interplanner distance dA and relative intensity 1/10 are shown in Table (1). 2.7

Spectral Prooerties 2.7.1

Ultraviolet SDectrum (vv)

The UV spectrum of amobarbital in 0.05 M Borax buffer (pH 9.4) and 0.1 M sodium hydroxide IpH 13) (Fig. 2) was scanned from 220 to 340 nm using DMS 90 Varian spectrophotometer ( 8 ) . It exhibited the following UV data (Table 2 ) . Table ( 2 ) .

?!! m

UV characteristics of amobarbital A(1%, 1 cm)

240

445

252

364

33

AMOBARBITAL

45

Fig. 1:

20-values

0

Characteristic principal lines of the X-ray powder diffraction of amobarbital.

NEELOFUR ABDUL AZIZ MIAN, ETAL..

34

Table 1:

X-ray diffraction lines of amobarbital sod.

28

dA

4.872 5.927 6.243 6.243 7.185 7.714 8.718 10.379 11.954 13.518 13.518 13.963 14.104 15.494 16.740 17.432 17.768 18.808 19.268 20.186 20.948 23.398 24.091 24.813 25.924 26.661 27.070 28.544 29.016 30.313 31.417 35.022 36.570

18.1367 14.9108 14.1581 14.1581 12.3031 11.4598 10.1428 8.5229 7.4032 6.5499 6.5499 6.3425 6.1489 5.7190 5.2958 5.0871 4.9918 4.7179 4.6064 4.3989 4.2406 3.8018 3.6940 3.5882 3.4368 3.3435 3.2939 3.1271 3.0773 2.9485 2.8473 2.5621 2.4571

100 81.631 72.106 72.106 46.369 73.364 97.699 30.481 46.908 31.056 31.056 41.876 49.568 77.318 38.569 63.407 57,872 61.718 57.836 52.552 60.819 43,853 29.439 31.020 40.977 30.301 42.092 27.534 27.749 28.540 32.674 22.933 22.789

--

--

1/10 %

-

1/10 = relative intensity (based on highest intensity as 100). dA = interplanner distance.

35

AMOBARBITAL

UV scan of amobarbital sodium in H2O is also presented in Fig. ( 2 A ) . It exhibitedleax at 207 nm and 240 nm. T h e s c a n was obtained o n LKB 4 0 5 4 U V / V i s spectrophotometer (8). Infrared Spectrum (Ia)

2.7.2

The IR spectrum o f amobarbital as KBr disc was recorded on a Perkin Elmer 580 B infrared spectrometer t o which an infrared data station is attached (Fig. 3). The structural assignments have been correlated with various frequencies (Table 3). (8) Table ( 3 ) .

I R characteristics of amobarbital

Freauency cm-

Assignment

2800-2950

Aliphatic C-H

3000-3200

C-NH

NH \

c = o

1696

NH band

1428 842

C-C strech

-

400-600 2.7.3

Alkyl

Nuclear Magnetic 2.7.3.1

&son-

Spectra

Proton Spectrum

The PMR spectrum of amobarbital in DMSO-ds (Fig. 4 ) w a s r e c o r d e d o n a V a r i a n ( F T 8 0 A ) NMR spectrophotometer using TMS as internal standard (8). Chemical shifts are shown in Table 4.

NEELOFUR ABDUL AZIZ MIAN, ET AL.

36

AMOBARBITAL

240

220

260

280

300

320

340

WAVELENGTH ( n m ) Fig. 2:

UV spectrum of amobarbital.

2 00 Fig. 2A:

250

350

L 00

UV spectrum of amobarbital sod. in H20.

'i OD

0 0

b

0

TRANSMITTANCE

I

h

Fig. 4:

PMR spectrum of amobarbital.

A

I

39

AMOBARBITAL

Table (4). PMR charxteristics of amobarbital Chemical shift ( 6 ) D D ~

Group

CH3 -C

0.9 m

C-CHZ-C-

1.1

C-CH-C C

1.5

- NH

2.1 2.7.3.2

13C

NMR Spectra

The 13C-NMR complete decoupled and off-resonance spectra of amobarbital in DMSO-dfi, were recorded on Joel FX-100 NMR spectrometer (8) using TMS as internal reference. Various carbon chemical shifts are shown in the Figs. 5 and 6. 2.7.4

Mass SDectrum

The mass spectrum of amobarbital (8) was obtained ( ) by direct injection of the sample into a Finigan-Mat 1020 GC/Mass spectrometer. The ionization beam energy was 70 eV. Figure (7) is a bar graph of the mass spectrum. Identification of the prominent masses is presented in (Table 5 ) . 3.

Synthesis general procedure ( 9 ) for the synthesis, of Monochloroacetic acid is amobarbital is presented. treated with sodium cyanide; the resulting cyanoacetic acid is treated with hydrochloric acid in the presence of ethanol, yielding the diethyl ester of malonic acid. The esl.~:c,in absolute alcohol, solution, is treated with the theoretical quantity of metallic sodium to replace one hydrogen of the CHz group and thereupon a slight excess of the theoretical amount of ethyl bromide, is added. The second hydrogen is similarly replaced by using iso-amyl bromide. The diethyl ester of ethyl, isopentyl malonic acid thus obtained is heated in an alcoholic solution, in the presence of sodium and urea to form amobarbital. A

Fig. 5:

13

C - NMR NOISE- DECOUPLED SPECTRUM

OF AMOBARBITAL

u)

f

w Q

m Y)

kL F i g . 6.13CNMR OFF- RESONANCE SPECTRUM OF AMOBARBITAL

fn fn

zcd

.. r.

43

AMOBARBITAL

Scheme: CH2ClCOOH

+

Monochloroacetic acid

CH2CNCWH

NaCN

CH2CNCOOH

ZC2HSOH * HC1

cooc2q I

P +

Cyanoacetic acid

Sod. cyanide

+

-

COOCZH5

I I

I

+

COOC2H5

+

f“Z

COOC2Hs

NH4C1

Diethyl malonate COOC2Hs

I I

+

4 H2

COK2Hs

Sodio-malonic ester COOC2Hs C H HC’ + NaBr

COOC2Hs HCNa

COOC2Hs

HCNa

Na

NaCl

I

C2HgBr

___f

I

COOC2H5

Ethyl bromide

Diethyl ester of Ethyl malonic acid

Diethyl ester o f ethyl-isopentyl malonic acid. COOC2H5 /‘ZH5

+

1 ‘CH2CH2CH(CH3)2 cooc2HS

-

CO H5 C2 4

co 1

NHZ

Diethyl ester of ethyl isopenryl malonic acid

I

CO

/

I 2co

(CH3)ZCHCH CH

- NH -NH

Amobarbital

I

+

2C2Hs0H

NEELOFUR ABDUL AZIZ MIAN, ET AL.

44

Table ( 5 ) .

The most prominent fragments of amobarbital

Relative intensity %

m/e

Fragment

197

156

78

141

,NH

4.

Metabolism

Amobarbital is readily absorbed after oral administration ( 5 ) . After an oral dose of 20 mg of the sod.-salt, a plasma concentration of 2 pg/ml is attained after 4 hours and this drops to about 1 pg/ml after 24 hours. Plasma amobarbital concentrations of greater than 50

pg/ml usually produce deep coma and are potentially lethal ( 7 ) . The estimated minimum lethal dose is 1.5 g (101.

Amylobarbitone crosses the placenta, is secreted in the milk, and is secreted in the saliva in concentrations with parallel those in the serum. The 3-hydroxy metabolite accumulates in renal function impairment; volume of distribution about 70 litrea (5).

Amylobarbital is metabolized by the liver v i a penultimate oxidation of the 31-methylbutyl

AMOBARBITAL

45

substituent to form a tertiary a l c o h o l , hydroxyamobarbital, which is an inactive metabol ite. About 40-50% of an oral hypnotic dose of amobarbital is excreted in urine as hydroxyamobarbital and its glucuronide conjugates. Less than 1% of an oral hyponotic dose of the drug is excreted in urine unchanged. Conjugates of hydroxyamobarbital excreted in feces or urine and or further oxidation products not yield identified, may account for the remainder of the dose (7). In 6 days, 80-90% of a dose is excreted in the urine and 4-5% is excreted in the faeces; of the excreted material, 30-50% is 3/-hydroxyamylobarbitone and 10-30% appears to be N-hydroxyamylobarbitone; less than 1% is excreted as unchanged drug in the urine (5). 5.

Toxicity

LDso (lethal dose) of amobarbital (oral) (10) in rabbits is 575 mg/kg and in rats 115 mg/kg. The estimated minimum lethal dose in man is 1.5 g; the blood-level associated with severe poisoning is 2 to 4 mg%. When the blood level is in the region of 1.5 to 2 mg% recovery is possible. Case example: A 51-year old man swallowed 20 g of amylobarbitone. Twelve hours after ingestion the blood level was 16 mg%. He recovered after dialysis (11).

A 77 year old woman was found dead after ingesting

about fifty-five (200 mg) amylobarbitone capsules in 4 days. Post-mortem levels were: blood, 16.3 mg%; brain, 11.9 mg%; liver, 36.2 mg%; stomach contents, 3030 mg; urine, 0.7 mg%. The blood level is stated to be one of the highest ever recorded (10). 6.

Uses Amobarbital and amobarbital sodium are used principally as hypnotics in the short-term treatment of isomnia for periods up to 2 weeks duration. Barbiturates appear to loose their efficiency for sleep induction and maintenance after this period of

NEELOFUR ABDUL AZIZ MIAN, E T A L .

46

time. The drugs are also used for routine sedation and to relieve anxiety and provide sedation pre operatively ( 7 ) . The drug may be used IV or IM to control status epilepticus or acute seizure episodes resulting from meningitis, poisons, eclampsia, tetanus, or chorea. The drug has also been used parenterally to control acute episodes of agitated behaviour in psychoses such as catotonic, negetivistic, or manic reactions, but has little value in long-term management of psychoses. Parental amobarbital sodium may also be useful in narcoanalysis, narcotherapy and as a diagnostic aid in schizophrenia ( 7 ) . Drug is given by mouth in a single dose of 100-200 mg as a hypnotic. Upto 400 mg may be given daily in divided doses as a sedative, the usual dose, however, being 30-60 mg daily ( 5 ) . 7.

Cautions

IV administered drug may cause respiratory depression, apnea, or hypotension, particularly if the drug is administered too rapidly. The drug must be administered slowly at a rate not greater than 100 mg/minute and personnel and equipment should be readily available for administration of artificial respiration. Hypnotic doses should be taken half to one hour before bedtime. The tablets may cause drowsiness on the following day. Persons effected should not drive or operate machinery. Alcohol should be avoided ( 5 ) . 8.

Methods

8.1

of

Analysis

Elemental Analysis C 58.39%,

8.2

H 8.02%,

N 12.38%,

0 21.21%.

Identification

(a) A saturated solution is acidic to litmus paper (3).

AMOBARBITAL

41

(b) Boil 0.2 g with 10 ml of 1N sodium hydroxide ammonia is evolved (4). (c) Incinerate about 0.1 g: the residue, when moistened with hydrochloric acid and introduced on a platinum wire into the flame of a Bunsun burner gives a yellow color to the flame (12). (d) A solution of 0.25 g in 5 ml of HzO is alkaline to litmus solution, on acidification with 2 M hydrochloric acid it yields a white ppt. (12) (e) Dissolve 50 mg in 2 m1 of a 0.2 percent w/v solution of cobalt+2 acetate in methanol, warm, add 50 mg of powdered sodium teteraborate, and heat to boiling, a bluish violet color is produced (12). (f) Dissolve 0.2 g in 5 ml of absolute ethanol, add 10 ml of silver nitrate-pyridine reagent and titrate with 0.1 M ethanol sodium hydroxide vs using 0.25 ml of thymolphthalein solution as indicator, until a full blue color is obtained. Each m l of 0.1 M ethanolsodium hydroxide vs is equivalent to 0.02483 g of CiiHi7N2Na03 (12). (g) Accurately weighed 450 mg of anobarbital was dissolved in 60 ml of dimethylformamide in a 125-ml conical flask. Add 4 drops of thymol blue TS, and titrate with 0.1 N sodium methoxide vs, using a magnetic stirrer and the precaution is taken against the absorption of atmospheric COz. One blank determination is performed. Each ml of 0.1 N sodium methoxide is equivalent to 22.63 mg of CiiHiaNz03 (4). ( h ) Triturate 0.6 g with 0.15 g of anhydrous sodium carbonate and 5 ml of water, add a solution of 0.45 g of 4-nitrobenzyl chloride in 10 ml of ethanol (96%) and warm on a water bath f o r 30 minutes cool, allow to stand for one hour, filter and wash the residue with 10 ml of 1M sodium hydroxide and then with water. The melting point of the residue, after recrystallisation from ethanol (96=%), is about 150" or about 168' ( 3 ) .

(i) The UV absorption of amytobarbitone in 0.1 N NaOH, is maxima at 220 nm (El%, 1 cm = 954) and 244 nm (El%, 1 cm = 365) (5).

NEELOFUR ABDUL AZIZ MIAN, ETU.

48

(j) Dry it at 105' for four hours it looses not more than 1.0% of its weight ( 4 ) .

8.3

Titrimetric Method

Determination of amylobarbitone has been carried out by titration in dimethylformamide and dimethylsulphoxide with 0 . 1 M pot. t.butoxide, pot. isopentoxide or pot. isopropoxide in toluene. The end point was detected potentiometrically (glass electrode vs calomal electrode) or visually with use of different indicators (13). 8.4

SDectrophotoietric Methodq 8.4.1

Absorption SDeCtrOSCODZ

D e Fabrizio made the suspension containing amylobarbitone in 50 ml of ethanol-acetic acid (1:l) centrifuge and apply 10 ml of the supernatent liquid to a column (50 cm X 2 cm) packed with alginic acid ( 4 g) that has been pre-washed with 2N-HC1 and ethanolacetic acid ( 1 : 1 ) wash the column with ethanol-acetic acid (1:l) at 1 ml/min and collect 100 ml of eluate adjust the pH of 2 ml of solution to 4 and that of second 2 ml portion to 10 with 0.02 N-NaOH, dilute each solution to 50 ml with HzO and measure the absorbance of the solution at pH 10 and (that of pH 4 in the reference cell) at 285.5 nm (14). 8.4.2

Infrared SDectroscoDg

Amylobarbitone can be identified (15) by stirring 100 g of e.g. liver o r kidney with HzS04 at pH 2 to 3 for about two hours. Repeat the extraction twice (one hour each time) with 0.01 M - H2S04 at pH 2-3, dilute the combined extracts to known volume with 0.01 M HzS04, and pass 50 ml of the solution through the column ( 4 0 cm X 2.5 cm) of sephadex G 25 (particle size 100-300 pm) and elute with 0 . 0 1 M - H2S04. Discard the first 150 ml of eluate. Collect the next 200 ml, and extract the barbiturates therefrom into Evaporate the combined CHC13 CHC13 ( 3 X 50 ml). extracts, dissolve the residue in CHC13, press 0.5 ml of the solution into a tablet with KBr (2 230 mg), and record the i.r. spectrum from 4000 to 700 cm-l.

AMOBARBITAL

49

Amylobarbitone can be identified from absorption bands in the regions 3200 to 3000 cm-l. Moss et al. (16) also analysed the drug using infrared

spectroscopy.

8.5

ChromatoRraDhic Methods 8.5.1

PaDer ChromatoRraDhg

Some paper chromatographic systems used for the determination of amobarbital have been summarised in Table ( 6 ) . 8.5.2

Column ChromatoRraDhg

Amylobarbitone can be separated by column chromatography using gel. The fractions eluted from a Sephadex G-25 column by 0.02 N - H2SO4 (pH 2.0) , universal buffer solution (pH 2.0) phosphate buffer solution (pH 4.0) or saturated aqueous Naz-B407, 0.3 N NaOH (3:l) (pH about 10.0) is shown to depend on the pH of the eluent and not on its ionic composition (18). ChromatograDhg

8.5.3

Different gas chromatographic methods used for the assay of amobarbital are summarised in the Table ( 7 ) . 8.5.4

Thin-Layer ChromatoRraDhp

A summary of different TLC methods used for the determination of amobarbital are given in the Table (8).

8.5.5

m h Performance Liauid ChromatoRraDhy

Several methods have been developed for the estimation of amobarbital by HPLC are given in the Table ( 9 ) . 9.

AcknonledemenThe authors wish to thank Mr. Tanvir A . Butt, Pharmaceutical Chemistry Department, College of Pharmacy, King Saud University and Mr. Babikir Awad


50

Mustafa, College of Applied Medical Sciences, King Saud University, for their secretarial and technical assistance respectively in preparing the manuscript. Table 6: Parameters used for paper chromatography of a i o b a r b i t a l

No.

1,

Support

Developing nolvent

Detection

Eeference

Paper Whatian No. 1

Ethylene dichloride

UP 251 n i

10

iipregnated with 10% solution of (NasPOc.12UzO) and dried,

2,

Paper Whatran No. 1 impregnated by dipping in 20% s o l u t i o n of fornaiide in acetone and dried,

51.NHtOH: benzene: CECh (6:3:13),

AgNO3 spray

17

3.

Ahatian No. 4

t i g h t petroleui

Paper exposed t o amionia vapour and then UV 254 n i ,

17

Table 7:

Summary of conditions used for GC of amylobarbitone -

Column support

Mesh

C-lass column (3 ft X 2 m m ) of 10% of UCW982.

80-100

Column packed with OV-17 - OV-101 2:3

--

Temperature

170'

150-300

Glass column (1.8 m X 4 mm) packed with 3% of SP-2250 DA

100-120

210-240

Borosilicate-glass column packed with 10% of SE-30 on Chromosorb W AW-

--

180'

DMCS

.

Flow rate

Sample

Reference

--

Blood

19

Nz carrier

Plasma

20

gas 40 ml/ min. a

--

--

21

Liver tissues

22

Continued (Table 7 . . . ) Column containing 0.2% of WG-H on Chromosorb W (HP).

--

225

-

--

(2.5 m X 0.3 cm) 3% of SE-30 Chromaton NAW HMDS (0.25 to 0.31

--

190

-

Carrier gas

Coiled glass column (6 ft X 2 mm) packed with 3% of SE-30 OV-17) supported on chromosorb W.

--

200' or 230

--

3% of SE-30 on Chromosorb 750

--

--

--

Sliva

26

G Ft column packed with 3% of OV-101 on Chromosorb WHP.

100-120

180

He as carrier gas

Tissues

27

(25 m X 0.31 mm) of

--

190"

N2

Plasma

28

Nz

.

Urine

23

Biological Fluid

24

mm).

VI

:ji

-

25

carrier

.-:is

I,

Table 8:

Summary of conditions used f o r the TLC of amylobarbitone

Plate

Developing solvent

Silica gel

HzO-methanol-aq. NH3 (40:lO:l).

Silufol sheets

CHC13 -acetone-aq. 22 to 24% NH3 (25:25:1).

Silica gel GF

Ethylacetate-methanolaq. NH3 (17:2:1).

Detect ion

Rf

Reference

-

--

29

6.52

30

--

31

254 UV

uv

Table 9:

S-ry

of HPLC conditions for the determination of amylobarbitone

~~

Column

(30 cm X 4 mm) Bondapak C18.

II

Stainless steel (10 cm x 5 PI) packed with Hypersil ODS

Mobile phase

Flow rate

Retention time

Hethano1:HZO (4:l)

2 mllmin

10 min.

0.1 M-NaH2P04:

2 illmin

--

1.16 ml/min

Sample

--

Detection

249

Reference

M

32

Blood

240 M

33

13.6 min

Plasma

200 M

34

--

Serum

195 M

35

methanol (3:2; pH 8.5).

(5 lu).

Y2

Reversed phase (125 cm X 4.5 IP) SAS Hypersil. A guard column (5 cmx 2.1) M of Co:Pel ODs.

Acetonitrile-5 mHtet.rabutyliuPonium phosphate solution (1:4).

(30 cm X 4 en) of p Bondapak C18.

Acetonitrile-phosphate buffer solution pH 4.4 (43:157).

3 mllmin

___________------Continued

I. ..

Continued (Table 9 . . . ) ~

~

Reversed phase column (C18).

Methanol-0.lM-phosphate buffer solution pH ( 4 . 0 )

--

Tissues

210 nn

27

(25 cm X 4 m ) of Nucleosil 7 C18

0.01M acetate buffer (pH 4.0) acetonit-

--

Serum

210 m

36

(7

w)

rile (7:3)

~~

NEELOFUR ABDUL AZIZ MIAN, E T A L .

56

10.

References

1.

The "Merck Index" 10th edition, p. 587, ( 1 9 8 3 ) .

2.

"Martindale", The Extra Pharmacopea" 26th ed. Eds. Norman W. Blacow and Ainley Wade, The Pharmaceutical Press, London.

3.

Bri t i s h Phar macopoe ia" He r Majesty ' s Stat ionary Office, London, p. 43 ( 1 9 8 8 ) .

4.

"The United States Pharmacopeia" 2 1 s t Ed. United States Pharmacopeial Convention, Inc. 12601 Twinbrook Partway, Rockville, Md. 20852, p. 52 ( 1 9 8 5 ) .

5.

"The Pharmaceutical Codex", 1 1 t h Ed. Pharmaceutical Press London, p. 46 ( 1 9 7 9 ) .

6.

"Index Noninum 1987" Scientific Documentation Center, Swiss Pharmaceutical Society, Zurich, p. 85 ( 1 9 8 7 ) .

7.

"Drug Information 88" American Society of Hospital Pharmacists Inc. 4630 Montgomery Avenue, Bethesda MD

The

20814. 8.

Mohammad Saleem Mian and Neelofur A.A. Unpublished data ( 1 9 9 0 ) .

9.

Remington's Pharmaceutical Sciences, 13th Editon, Mack Publishing Company Pennsylavania, p. 1147, 1965.

10.

"Clarke's Isolation and Identification of Drugs" 2nd Ed. The Pharmaceutical Press, London ( 1 9 8 6 ) .

11.

Terplan, N. and Unger, A.M.

J. Am. Med,

Ass.

Mian,

198, 322

(1966). 12.

British Pharmacopeia, Her Majesty's Stationary Office, London V ol . 11, p. 583 ( 1 9 8 0 ) .

13.

Bacnrata, M.; Blesova, M; and Bezakova, Farm. Obz. 5 2 ( 5 ) 195-207, 1983 (Czech.).

14.

De Fabrizio, Fabrizio. J. Pharm. Sci. 6 6 ( 6 ) , 811-813, 1977.

AMOBARBITAL

15

I

51

Popova, V . I . ;

Mynka A.F.; and Kramarenko. Farmatsiya

2 6 ( 5 ) 40-44, 1977. (Russian). 16.

Moss, W. Wayne; Posey, F.T.; and Peterson, P.C. 2 5 ( 2 ) , 304-313 ( 1 9 8 0 ) . Forensic

17.

Ahmed Z.F. et al. J . Pharm. Sci. 55, 433, 1966.

18.

Popova V.I. Farmatsiya 2 7 ( 2 ) 34-35, 1978.

19.

Budd, Robert D. et al.

m,

JI

Anal. Toxicol. 6 ( 6 ) ,

317-320, 1982. 20.

Ithakissios, Dionyssis,

JI

Chromatodr. sci l8(2),

JI

Assoc. Off. Anal. Chem.

88-92, 1980. 21.

Black, Donald, B.

et al.

6 5 ( 5 ) , 1054-1058, 1982.

22.

Dilli, S . ;

and Weekely, A. J- Chromatodr. 1 9 5 ( 3 ) ,

349-358, 1980. 23.

Kinsella, Helen C. et al. J. Pharm. Pharmacol. 3 1 ( 3 ) , 153-156, 1979.

24.

DementCva, N.N.; and Kuleshova, M.I. Farmatsisa 2 7 ( 5 ) , 35-37, 1978.

25.

Fontan, C.R. and Hill H.H. Jun. J- Chromat. m(1), 249-253, 1979.

26.

Dilli, Sergio, Pallac, Dilrangan. J- Chromato.

m(l),

113-118, 1980.

27.

Balkon Joseph; Prendes Diane; and Viola Joanne

-Anal. -Toxicol. c ( 5 ) 228-30,

JI

1982.

JI Anal.

28.

Wallac, J . E . ; hALL, 1.r.; Harris, S.C. Toxicol. 2 ( 4 ) , 178-180, 1983.

29.

Bress, William; et al. Clin Toxicol. E ( 2 ) , 219-221, 1980.

30.

Chmel, K. Cesk. Farm. = ( l o ) ,

456-459,

1978.

NEELOFUR ABDUL AZIZ MIAN, E T a .

58

m.

31.

Caplain, Yale, H. et al. J. Forensic 745-751, 1979,

32.

Hulshoff, A , ; Roseboom, H ; Chromatogr. 186,535-541, 1979.

33,

Gill, Richard; et al. Chromatogr. m ( 1 ) ; Biomed. Appl. x(l), 117-123, 1981.

34.

24(4),

and R e n e m a J.

J.

Christofids, John A . and Fry, Denys E. Clin. Chem.

26(3), 499-501, 1980.

35.

Kabra, Pokar M. et al. Clin. Chem. 24(4), 657-662, 1978.

36.

Nishihara, K. et al. Bunseki Kagaku, 3 5 ( 3 ) , 272-277, 1986.

wlpivacaine Terry D. W i l s o n

Sterling Resear& Group

Rensselaer, New York


59

Copyright 0 1990 by Academlc Press. Inu. All rights of reproduction 111 any fonn recerved

TERRY D.WILSON

60

1.

Foreword

Bupivacaine is a putent lcarg -a local Mesthetic of the mnide class which is available w i t h or wiepinephrine (as the bitartrate, 1:200,000). It is by 1infiltmticm and for p e r i w nerv8 block and c a m and lurmbar epidural block. B u p i v a d m is also available as a

sterile h-ic solution Containing mid injection (spinal block) ( 1 , 2 ) . 2.

for subarach-

pescr 2 . 1 panenclature B u p i v a d n e HCl

-in

2-Pipd-

-1)

d, l-l--1-2

' de ,1-1-N(2 ,6-dimethyl-,moolohydrochloride, pwnrhydrate ' ,6 I-pipeeol~lididemanohydro-

chloride m y d m t e 2.2

Fonrmla C H N 0-HC1.H 0 18 28 2

2.3

2

Nolecular Weicht oride mnchydmte base

0 II

CI

CIH,

342.9 288.4

NHD Me

Me

61

BUPIVACAINE

2.5

CA Reaistrv Numbers base [2180-92-91 hydrochloride, anhydrous [ 18010-40-71 hydrochloride, mnohydrate [ 14252-80-31

2.6

Amearme,

2.7

Recosnized m c r e Forms The forms of bupivacahe hydrochloride recognized by the U.S.P. include the bulk drug and the following formulations (1,3).

Color, odor Bupivacaine hydrochloride is a white, crystalline pcrwder.

odorless

wzpivacaine in Dextrose Injection, 7.5 q hydrochloride per mL wrpivacaine and Epinephrine Injection, 2.5 and 5.0 mj hydrochloride per mL wrpivacaine Hydrochloride Injection, 2.5, 5.0 and 7.5 q hydrochloride per mL synthesis and Resolution 3.1

synthesis The synthesis of bupivacaine originally was accamplishd in Sweden by Ekenstam and was reported in the literature and in a U.S. patent (4,s). This method is illustrated in Figure 1. Briefly, malonic acid ethyl ester 2,6-xylidide resulted frum heating 2,6-xylidine with diethylmalonate. The recrystallized monoxylidide was converted to the is0nit.msamdlonic ester xylidide which was reduced to the amhe. D e l t a brumobutylamhcmalonic ester xylidide was formed following the substitution reaction on its precursor. Finally, the cyclization reaction to bupivacaine base was completed under acidic conditions.

3.2

Resolution The optical isamers of (+/-) bupivacaine were resolved using (+) tartaric acid in boiling 2propanol. The (+) isamer precipitated first as the (+) tartrate while the (-) bupivacaine isamer salt of (+) tartaric acid was recovered frum the resolution liquor (6).

TERRY D.WILSON

62

SYNTHESIS 0 II

Me

0 II

alcohol

- - CH, - C - OEt + ZHN

Et 0 C

*

Me

CHCI,, NOCl

b

Mk

0 Zn, HCOOH @

benzene

NaOEt, Br

+

- (CH,), - Br

alcohol

i'

Md

0

HCI

@

NaOH

b

Mk

n-butyl Br n-BuOH K2C03

Figure 1.

synthSsi.8 of bJpivaCaine

b

63

BUPIVACAINE

4.

Phvsical Properties 4.1 Meltina point The reported melting points of bupivacaine base and

salts as well as the resolved isomers are given in Table 1.

4.2

4.3

mica1 Rotation optical rotation results found for resolved optical isamers are s h m in Table 2. Elemental Analvsis

Results for e l m t a l analysis of bupivacah are s h m

in Table 3 .

4.4

Ionization Constant The pKa values of bupivacaine and its resolved and Aberg isamers were determined early by F’r-er and are listed in Table 4 (10). While these values have been often quoted in the literature, the method used in their detenchation w a s not described, although it could have been the solubility method. A more recent potentiometric study revealed similar results along with an enthalpy of ionization of 8.19 kcal/mol for bupivacaine (11).

4.5

Partition Coefficient The partition coefficients of bupivacaine base isomers have been meamred in various systems. widely divergent results of these studies dependent on the solvents in use are listed in Table 5.

4.6

Solubility The solubility of bupivacah hydrcchloride has been described as 1 in 25 of Water (40 w/mL), 1 in 8 of alcohol (125 mg/mL) and slightly soluble in acetone, chlorofonn and ether (2,13). In addition data s h m in Table 6 for bupivacah hydrochloride solubility has been obtained showing the decreased solubility of the racemate carpred to the resolved isomers. Figure 2 shcws a pH/solubility profile obtained for (+/-) bupivacaine hydrochloride with the characteristic break in the cuwe at pH 6, below which further increases in hydronium concentration fail to increase bupivacaine solubility (14).

TERRY D.WILSON

64

Table 1

Melt-

Points of Bupivacaine

Form

Isgner

Melth mint " C

Reference

base base base base

(+/-I (+/-I (+I (-I

107.5-108.0 107-108 135-137 135-137

4 8 6 6

HC1 HC1

258.5 258-259 255-256 250-255 258 260 258 255-257

HCl

HCl HC1 HCl HCl HCl

Table 2 of wrpivacaine Iscmers

optical -tion

Form base base HCl HCl HC1 HC1

ISamer

(+I (-1 (+I (-1 s (-1 R(+I

25

Itemration

81 80.9 12.7 12.3 12.0 12.7

5%inmethanol 5%inmethanol

"D

+ +

--

Reference

2% inwater

2% i n w a t e r

2% in water 2% in water

Table 3 Wlpivamh Elemental Analysis

Form

ISOmer

%C

base

(+/-I

74.96

% H 9.78

L N 9.71

L O

Referenee

5.54

8

BUPIVACAINE

65

Table 4 wrpivacaine Ionization constants

rsKa

Reference

8.09 8.09 8.09 8.17

10 10 10 11

Table 5 wrpivacaine Base Partition Coefficients organic

Partition Coefficient

Reference

oleyl alcchol/ water n-hem/ pH 7.4 lxlffer oleyl alcohol/ water oleyl alcohol/ water

1565

10

27.5

12

1624

10

1603

10

Aclueous

Table 6

iquems Solubility of wrpivacaine Hydrochloride IsQner

Solubilitv (rm/mLJ1 0.83 23* 64* 64*

*extrapolated

J a

Reference

7.4 3 3 3

12 10 10 10

0 0 v.-

0 0 0 0

r-

-M

7

0 0 0

. N

67

BUPlVACAlNE

Investigations on the solubility of bupivacaine base have shown an irnrerSe tenperature dependeme. Results fourd for solutions in 0.5 M and 0.7 M phosphate buffers (pH 7.4) and in 1-4 mM NaOH (pH 10.43-11.86) are shown in Table 7 where a 1 mM solution is equivalent to 0.288 mg/mL (15, 16). Little ionic strength effect from 0.1 to 1.5 M was observed on the solubility of (+/-) bupivacaine HC1 or the resolved kumers at pH 7.4 and 23°C h another study (10). 4.7 !3De&ral

-

4.71 Mass The mass spectrum of bupivacaine is shown in Figure 3 resulting f m a methane chemical ionization as obtained on a Nermag R-10-1OC mass spectrameter with a direct insertion probe, a 160°C source temperature and an electron e n q of 94.4 volts. The molecular ion is seen at m/z 289 (MH') while+the peaks at nQ 317 and 329 correspond to MH + C H and MH + C H The peak at m/z 140 c o d & to the l-b&$lpiperidine fragment (17).

.

4.72 Nuclear Mametic Resonance !%ectrm The proton magnetic resonance Spectrum of

bupivacahe is shown in Figure 4. It was obtained on a Jeol GSX 270 for a solution h D 0. The spectral interpretation is listed in A l e 8 which was made possible usmeal shifts, intensities, literature values and 2-dimensional m y results which are shown in Figure 5 for bupivacaine. Singlets are seen for the two methyl groups on the phenyl ring and the exchangeable protons whereas the aliphatic chain methyl exhibits a triplet. The piperidine methine is a doublet while the nonequivalent methylenes of the piperidine ring appear as a doublet of doublets. Integration of the four exchangeable protons is slightly low as a result of the fast pulse delay (3.0 sec) used in accumulation of the Spectrum (17). The 13C-nmr decoupled spectrum of bupivacaine is shown in Figure 6 as obtained on the same

TERRY D.WILSON

68

Table 7

solubility of wlpivacaine Base ooncentration Found (mM) 0.7 M phosphate buffer buffer

0.5 M p h w t e 14.5 14.9 25 34.5 37 48 54.8

1.35

-

0.85

-

0.481

0.57 0.465 0.374

0.363

-

-

1-4 W I

NaOH

0.375 0.318 0.313

-

I

2

n

*

0 0

0

v)

n

0

w

r

1

2

1

1

1

0

9

8

7

6

5

4

3

2

1

(

BUPIVACAINE

71

Table 8

i

No. H 0.84

3

1.20

2

1.5 1.8

- 1.8

- 2.0

Assicnmnent CII of the aliphatic

4 3

tothenrethineofB 2.13 2.38

6 1

piperidhe f , h** * 2 of the phenyl j methylem adj.

tothemethineofthe 2.99

- 3.21

3

piperidine f of the aliphatic

adj. t o t h e N o f

the piperidhe anl y2 3.65

1

4.12

1

4.72 7.2 7.0

-

**:

4 3

of a rn equivalent btheN the Piperiaine d,g of the naQl

CIIadj. t o t h e N o f

the

piperidh e -1e-k rzH * 3 of the phenyl ring 1

Individual assigments are mce&ain ard s h i f t values m y be intadlanged.

TERRY D.WILSON

12

m- 0 I,

O

Figure 6 .

13C-n~~lear magnetic bupivacaine.

spztrum of

TERRY D.WILSON

14

i n s m t as the pr spechum. Assignments are listed i n Table 9 and were made based on chemical shifts, intensity, distortionless enhancement by polarization transfer (DEPT) experhnents and 2-dimensional hetemnuclear correlation (HETcoR) experiments. The results from the l a t t e r is Bhawn in Figure 7 w i t h the proton spectnrm on the y-axis and the carbon Spectrum on the X - ~ S(17). 4.73 Infra-red The infra-red absorption spechum of bupivacahe HCl is shown in Figure 8. It was taken on a N i c o l e t 20SX FT-IR for a 1% KBr pellet (17) 4.74 u l t r a v i o l e t

spectnrm of bupivacah HC1 was obtained on a Varian EMS-200 ter. The scan f r a n 300-200 m on a 0.1 q/mL solution in water is shown in Figure 9. The wavelength of a maximUm absorbance seen is 262 m, ~ f r e r ea molar absoxptivity of 473 M - ~an-1 was found.

An ultra-violet

4.8

Dissolution official dissolution procedures for bupivacahe have not been established because of the parenteral nature of bupivacahe pmducts. Dissolution methcds were described, huwever, for use with local anesthetic bases an3 their 3-hydrcocy-2-naphthoate salts (15,18). Water jacketed beakers were used w i t h magnetic stirring (360 rpxn) using dissolution media of 0.5 M or 0.7 M phqhate buffer a t p-I 7.4. withdrawn samples were assayed spectraphotometrically a t 263 m for the bases or 350 m for the salts.

15

BUPIVACAINE

Table 9

memical s h i f t tm, 12.6 17.1 19.2 20.7 22.2 25.0 28.8 52.0 56.0 65.7 128.2 128.4 131.8 135.6 168.3

*:

'1Ms)

Assianment a b C

*d

*e *f g h

i

1 m n 0

Indiviltual assignments are uncertain and s h i f t vdlues may be interchaqed.

TERRY D.WILSON

76

P i p 7.

Hetarmuclear correlation e2q2eriKant for Ixlpivacdine.

I0 T 06

Gb

02 3 3 N b L l I WSrvbal %

09

0

3

132-

TERRY D. WILSON

78

0 600 0,600 ABS

1 I

1

0.360,

0.240-

1,120-

-

F

W 9.

Ultraviolet spectnrm of hplvacalne.

BUPIVACAINE

79

4.9 Identification

wlpivacaine hydrochloride drug substance is identified in official mnpendia by severdl tests (13,~). An infabsorption spectnrm taken on the extracted and dried base form shows the same maxima as that of a bupivacaine reference stardard. ultraviolet absorption spectroscapy is also used to identiw bupivacaine hydrochloride. A 1 in 2000 solution in 0.01 N HCl shows the same absorption maxima and minima as a reference stardard plus the absorbance at 271 nm is within 3% of that of the reference standard. The aqueous layer remaining from an alkalinized and extracted solution of the salt also responds positively to the diloride test. Finally, the melting point of a salt formed when trinitraphenol is added to a bupivacaine HC1 solution, serves as an identification test. Identification tests for bupivacaine HC1 drug products have also been developed. 'Ihese include a Tli2 procedure for Wzpivacaine in Dextrose Injection and the organic nitrogenous base infrared absorption spectroscapy test applied to Bupivacaine HC1 Injection (3,20).

5.

Methods of Analvsis 5.1 Titrhtric

Wzpivacaine can be detennhed by a titrimetric procedure in which the ccnnpound is dissolved in glacial acetic acid. Crystal violet is used as indicator and the solution is titrated to a green end-point with 0.1 N percNoric acid. Each mL of 0.1 N perchloric acid at this point is equivalent to 32.49 mg bupivacaine HC1 (13,19)

.

5.2 Ultraviolet

OttnQetry

ultraviolet spectraphotametry has not been generally applied as a routine or ccnrcpendial method for bupivacaine analysis althuugh reports have appeared making use of it. These irnrolved dissolution procedures in which the 3-hydroxy-2-naphthoate salt and bupivacaine base were assayed by W spectraphotcmtry using 263 nm and 350 nm as analyticdl wavelengths for the base and salt respectively (15,18).

TERRY D.WILSON

80

5.3

(3lrimatoclra&y

5.31

Thin Laver (3lrima-W Thin layer chmnatcgraphy has been used to analyze bupivacaine and has also been used as an identification test and a test for chrcnnatographic purity (13,3,20). It was also used in biological test* to purify extracted rabbit urine (21) and to separate ccanporaents of extracted equine urine (22). conlitions employed in these procedures are listed in Table 10.

5.32

Gas mtoclramv and GOMS

as chroanatography is the method of choice for measuring lyivacaine levels in biological

fluids in cldcal studies. W e a multitude of such clinical studies can be found in the literature anly a few actually describe chmnatographic conditions used. Gas chramatosraphy has also been used for bupivacaine assay in anilnal studies and in dissolution Studies. The conditions enplayed in these studies are listed in Table 11. Impmemnts in methodology indicated in this table include increased use of the more sensitive and specific rlitmgen and nitrogen/phasphonts detectors along with the ability to detect metabolites as well as the application of capillary column Gc to further increase sensitivity.

Wlpivacah has also been analyzed in biological sanlples u s h j Gc-Ms procedures. conditions for these reprted studies are listed in Table 12. 5.33

Liauid Chranatoclrarh~ have been dweluped for analysis of bupivacaine in both biological specimen and dosage forms. These methcds are classified here as achiral or chiral c b p n d h g on whether or not separation of the (+) and (-) enanticaners was claimed. conditions used for the achirdl methods, all reverse phase, are listed in Table 13.

Hi&

performance

Hm% proaedures

81

BUPIVACAINE

Thin Lay-

Table 10 Chrmatography of Bupivacaine

Stationary Phase

Mobile Phase

Visualization

Silica gel

butyl alcohol: water:dlcahol:

Icdoplatinate

0.25 mm

3

gl .HaAc

(6:2: 1:1)

Silica gel 0.25 mm

hexane: isoPrpPylW (97:3)

Silica gel

ethanol

G

Silica gel G

(96%)

20

Patassium iodabislarthate

13

isoprapanol: chloroform: annnonim hydroxide

21

chloroform: lIEthano1

22

(10:89.5: 0.5)

HP Silica gel 0.2 mm

(9:l)

TERRY D.WILSON

82

-

FID

210

30

FID

225

30

m

FID

230-280

18

5%OV-17

1.8 m

FID

190-250

23

-

10% PEG

1.5 m

FID

214.5

62.2

-

18

1.5 m

FID

265

31.6

20

15

FID

215-235

30

-

27

FID

250

40

50

28

2.5% SE-30

2

3%OV-17

5'

3% OV-17

1.8

m

23 24 25 26

-2

3% OV-17 3%W-17

6'

3% SE-30

1.8

m

10%OV-1 (3%OV-17)

1.2 (1.8

m

Nit.

200-250

35

25

29

3% OV-17

1.8 m

Nit.

180-240

20

50

30

Nit.

170

5

3

31

Nit.

-

-

10

Nit.

260

30

-

32

Nit.

-

-

1

34

Nit.

210

30

50

35

m) Rms.

carbo-

Sarr

W a x Z w

10m

3% OV-17

6'

5%OV-17

1.8

KLMI

m

m.

Fhos. CFmX

capil

57cB

10

2 m

3%OV-101

-

m

Nit. nitmgen detector N i t . Fllos. nitragen phosphoraus detector

-

33

83

BUPIVACAINE

Table 12

Gc-m Analysis of wrpivacaine

Instrument

column

IXB 9000s

-

70 w

21

Varian 140-

3% SE-30

88 w

36

HP 5995A

3% OV-17

70 ev

37

-

38

-MAT31lA Ins

I3a3 2091-710

3%

m Table 13

Achiral H P E Methods for wrpivadne

Flow

column

Mabile Fhase

Detection

Rate

Detection Limit

hlulnin)

olu/nlL)

Reference

OD6

m : 2 8 nM R1os. Buffer pH 6.8 (65:35)

W-263

2

-

20

C18

MeQ€I:50 nM R1os. Buffer pH 5.0 (60:40)

W-254

1

50

39

C18

m : 5 0 nM Fhos. wrffer pH 5.8 (25:75)

W-210

0.9

50

40

c8

n m 1 0 nM Fhos. Buffer pH 2.4 (8:92)

W-210

1.6

100

41

C18

ACN:50 nt4 Fhos. Buffer pH 3.5 (30:70)

W-210

1

30

42

TERRY D.WILSON

84

chiral separations of bupivacaine optical isamers have been successfully performd usQ -acid glycopmteh columns originally lab p & since ~ they were unavailable copmnerc cially, alone or in ccnnbination with other columns. The original camercial c o l m of this type, 'Rlantiopac,' was marksted and s h a d broad amlicability to a laqe nunber of r a d c drug separations although it suffered fm a lack of ruggedness. A second generation a -XP column was used in the most recent stud$ listed in Table 14 along with conditions for these separations. 6.

Bioloaical Fate and pharmacokinetics 6.1 Absomtion The absorption, distribution, metabolism and exffe-

tion as well as the pharmacakineics of bupivacaine in man have been extensively reported on and reviewed along with other local anesthetics (12,49,50,51).

Since the drug is available for administration by a variety of mutes as indicated in the forward section above, a variety of pharmacokFnetic consequences would be peak concentrations faund in venous or arterial plasma samples over all administration mutes reported, as summarized by Tucker and Mather, ranged between 0.12 and 4.95 p g / a with t h of peak plasma amcentration between 5 and 35 mirmtes (12). when the data was adjusted to peak maximum concentration in p g / a per 100 n g bupivacaine dose, however, the range w a s ccnrrprassed to 0.2-1.55.

-.

The effect of route of administration on bupivacaine absorption into the systemic cirr?ulation can be further delineated by ccanparing epidural to subarachnoid administration. In the f o m a two phase absorption has been measured with a rapid initial phase follcwed by a slaver second phase (Wrption t l / 2 values of 0.12 and 6.0 hours, respectively) (12,51). Following subarachnoid administration, hwever, no rapid initial absorption was noted (t1/2 = 0.83 hr) while the slcrwes final phase had a t1/2

BUF'IVACAINE

85

Table 14

chiral HPIX: Methods for wlpivacaine

column a

1

m

Mobile phase

50 mM m. Buffer, pH 7.01 20 nt4

al=

m.

Buffer,

PH

Flaw

Detection

Rate /mIsminl

Reference

W - 2 15

0.5

1.4

43

W-215

0.5

1.9

44

0.3

1.4

45

7.1:2-propanOl (94:6) 20mphos. Buffer, p H 7 :2-propano1 (90:10)

al=*

alAGP*

alAGP**

-

8mMphos.

W-215

0.3

1.4

46

10 mMphos.

W-215

-

1.5

47

w-210

0.8

1.3

48

Buffer: 21(91:9)

Buffer,

PH

7.26: 2-

propano1 (94:6)

aim**

a

* ** *** alAL;p

10 n@lphos. Buff-, PH 7:2-PrUpanol (91:9)

separation factor (k12/k'l)

labpackedwlumn first gemxation canmemidl wlunm

sec#nd ganeratian ccanrercial wlunm alphal acid glycaprpteh wlumn

TERRY D.WILSON

86

of 6.8 hr. These diffhave been attributed to differences in administration site vascularity and extent of local binding. In any case the fraction of dose absorbed into systemic cimulation fm these sites has been as 94-96% (51). 6.2

Distribution, Bindinu and PharmaCokinetiCS Following absorption into the systemic circvlation bupivacaine is exposed to both tissue and blood binding. High levels of lung binding of lrmpivacaine have been &served in rat tissue slices (52) wha-eas circulating blood binding occurs w i t h two plasma P ' i a -acid glycoprotein, whic31 contains high-affinity: Im-capacity sites and m, with lm-affinity, high-capacity sites (12). Inmases i n plasma levels of the former are associated w i t h various disease states and follming surgery tihi& can account for higher total blood bupivacah concentration a t that time. Analysis for free bupivacaine, however, showed little increase following choleq&e&my in 7 patients. Prolmged epidural bupivacaine infusion i n post operative patients also resulted in high total plasma concentrations but no toxic effects due to protein birding (12). The plasma binding cuwe for bupivacaine plateaus below 2 pg base per mL plasma a t 96% bound

-

(53)

-

These distribution and birding @u?mmnaare reflected in data Shawn in Table 15 the high

is related to extensive tissue and plasma p % k n binding. !Che clearance and half l i f e values are aepenaMt on site of administration as discussed above w i t h subarachnoid bupivacaine eliminated more rapidly than epidural. Yaurrg patients eliminate bupivacaine faster than old patients and the method of calculating these paramters -( or noncaprtmntal analysis) had l i t t l e effect on the values obtained. V

6.3

Metab0l i s m and Excretion wlpivacaine and other d d e local

are mainly eliminated thraugh liver netabolism w i t h only 2.6% appearing i n the urine undmqed (12,51). Anmq the mtabolic pathways available, Figure 10 indicates those most czcmonly utilized i n mamlnals including man. Para- and ortho-hydmxylation are

BUPIVACAINE

87

Table 15 Fhannacokinetics parameters for wlpivacaine Volume of Distribution

steady state

v[L) -dSs

clearance ~Wmin)

TennFndl

Half Life thr)

AdnlhiStT.

Route

Reference

73

0.58

2.7

12

74

0.45

1.9

33

0.51

7.6

54

0.33

9.8

54

0.46

4.8

34

0.28

4.5

34

0.61

4.7

55

67

0.51

2.4

56

68

0.52

2.4

56

66

0.61

1.8

57

TERRY D.WILSON

88

METABOLlSM

nBu

Me

OH

PPX H

F

W 10.

Manrmalian matabolic pathways for klpiMckinB.

I 0

BUPIVACAINE

89

predominant in man, followed by conjugation or N-dealkylation to the htenned~ ' ate 2,6-pipecolylxylidde (PPX). This can then be phydmqlated, and conjugated or hydrolyzed to 2,6-xylidde and pipecolic acid. In man and rats the hydrcorylated P -P ' te with less N-dealkylation and hydrolysis while in n m l q s hydrolysis is the major metabolic pathway (12). 7.

ktennination in Bodv Fl~ids Bupivacaine has been meamred in whole blood, plasma, senrm, ce3tebrosphal fluid and urine. The majority of the methods used for these assays were gas chrcanatographic and gems, with Table 16 listing methods and fluid assayed.

Acknowledqement. The author wishes to thank MS. N. L. valcik for marnwxipt typing assistance, Dr. G. A. and me;mbers of the Wlecular Characterization Section of Sterling Research Group Rensselaer as noted in reference 17.

-

TERRY D.WILSON

90

Table 16 Refereme for WlpiMCaine Detennination in Body Fluids IVkthod:

Gc

G c m

HPIX:

Fluid

Plasma

Blood

27, 23, 25, 29 59

senrm

30, 32

-

CSF

24, 29

-

Urine

3a

46, 41

-

41

21

BUPIVACAINE

91

References 1.

Pnvsician's Desk Reference, 43rd ed., Medical Econcnnics Co., Oradell, N.J., p. 228 (1989).

2.

Martindale, Reynolds, J.E.F. ed., 29th ed., ceutical Press, London, p. 1209 (1989).

3.

The U.S. Fhannaaxeia, 22nd ed., U.S.P. Convation, Roclwille, MD, p. 193 (1990).

4.

pharma-

Ekenstam, B., Egner, B. and Fettersson, G., Acta Chem. 11, 1183 (1957).

-Scand.

5.

Ekenstam, B.T., U.S. Patent 2,955,111 (1960).

6.

Tuller, B.F., J. Med. Chem.,

14, 891

(1971).

7. 8.

Maxk Index, loth ed., Merck and OO., Rahway, N.J., p. 1466 (1983).

9.

IQhnert-Brandstatter, M., IQfler, A. and Kramer, G., Phann. 42, 150 (1974).

r m e r ,P. and Aberg, G. I Acta pharm. SUecica, 8, 361 10. F (1971).

11. Kamaya, H e , Hayes, J.J. and Ueda, I., Anesth. Anala.1 62, 1025 (1983). 12. Tucker, G.T. and Mather, L.E., 'Pmperties, Absorption, and Disposition of Local Anesthetic Agents, I in Neural Blockade, 2nd ed., Cousins, M.J. and Bridenbaugh, P.O. eds., LippincOtt, Philadelphia, p. 47, (1988). 13.

Br. &armacoDoeia, Her Majesty's Stationery O f f i c e , London, p. 80, (1988).

14. Portmann, G.A., data.

S-1-

G W ,

unpublished

TERRY D.WILSON

92

15.

Nakano, N.I. and SetOya, A., J.

pharm.

622 (1979).

Phamacol., 2,

16. Nakano, N.I., J. phann. Sci., 68, 667 (1979).

, Gangell,

17. McNaughton, L.A.

S.J. and M c G u h , T.A. Group, unpublished data.

Sterling

18. Nakano, N.I., Kawahara, N., Zdya, T., pharm. will., 2,936 (1978). 19.

U.S. pharmacopeia, op cit, p. 194.

20.

U.S. Pharmacopeia, up cit, p. 195.

21.

Eouche, R. and Ihoest, G.

22.

(1976).

et all Chean.

51, 223

phann. Acta Helv.,

Chay, S., Houston, T., et 61, J. V e t . 8 , 181 (1985).

Woods, W.E.,

,-

23.

Reynolds, F. and Beckett, A.H.

p.

24.

W i l k i n s o n , G.R. and Lurd, P.C.,

Anesthesiol,,

25.

Dennhardt, R. Fricke, M. and Stockert, G. Anesthes., 2, 59 (1978).

26. 27

,

704 (1968). (1970).

pharm. pharmac.

,

ZylbercKatz, E., G r a n i t , L. and 1573 (1978).

24,

G.T.,

,-.

20,

2,483

, Reaim.

Levy, M., Clin. Chan.,

32, 255 (1970).

28.

Verheesen, P.E., Brcanbacher, P.J., J. Clh. Chem. C l h . B i d e m . ,

29.

Park, G.B.,

H.M., et all

u,351 (1980).

phann. Sci.

30.

Lesko, L.J.,

31.

Wum, A.G.

Erdtmansky, P.E., 603 (1980)

, 69,

.

Rruwn, R.R.,

et 61, JI

Ericson, J., Ostheimer, G., e t a l l clhrcoMt4QT., 182, 226 (1980).

,

,

KlWf, J.W.

I

and de Boer, A.G.

57, 527 (1982).

,

JI

BUPIVACAINE

93

e t al, C l h .

32

Densan, D., Cayle, D., Thcnnpson, G., PhafiMCol. ma., 3,409 (1984).

33.

N o b l e , D.W., Smith, K.J. and Ixlndas, C.R., Anesth., 59, 735 (1987).

34. Veering, B.T., Bunn, A.G., van Kleef, J.W., Anesth. Analcf., 66, 965 (1987). 35. 36. 37.

Chan, K., Ther. Druq M o n i t o r . ,

., Smith, R.L.,

.

P.M.,

39. Wiegarrd, U.W., QlrmMtosr.

. S t i t t s , J.M.,

Ha, H.R.,

63, 448

sundberg, A.E.,

e t al, e t al,

Edstrom, H.H.,

65, 753 (1986). Chm, R.C.,

, 311,

Lanz, E., et all JI

218 (1984).

Funk, B., Gerber, H.R., (1984).

et al, Anesth. Anals.,

Lindberg, R.L., Emto, J.H. and Pihlajamaki, K.K., Chrmatow., 383, 357 (1986).

42. Adams, H.A., B i s c a p i n g , J., Ludolf, K., Ansth. , 12, 53 (1989). 43.

et a l l B i d .

Anesthesiol., 55, 611 (1981) Anesth. AnalS. I

41.

Kuhnert, B.R.,

et al,

(1989).

C a l d w e l l , J., M o f f a t t , J.R. , 4, 322 (1977)

Mass smct

38. Axelsson, K.H.,

40.

11, 567

Br. J.

JI

e t 61, m i o n .

Hermansson, J., J. chmmatoar. , 269, 71 (1983).

44. Hermansson, J., J. Qwmratoar., 298, 67 (1984). 45. Schill, G., Wainer, I.W. and Barbn, S.A., QrrmMtoar., 2, 641 (1986) 46.

Lse, E.J.,

47.

-,

&KJ,

S.B.

and

203 (1987).

ura&ia

J., S-,

, 24, 520

QzrCuMt0ar.i

420,

K. and Sandberg, R., -to-

(1987).

48. Walhagen, A. and Edholm, L.E., (1989)

.

T.L., J.

J. Lia.

J. C!hrcmtour.

, 473, 371

TERRY D.WILSON

94

49.

Tucker, G.T. and Mather, L.E., Clh. pharmacokin., 4, 241 (1979).

50. Tucker, G.T.,

Br. J. -the,

2 , 717 (1986).

s, 283

51.

Bunn, A.G., C l i n . pharmacokin.,

52

m t , C., Anderson, R.G., Ryrfeldt, A., et al, Acta. pharm.

53.

(1989).

., 4,103 (1979).

Tox

Tucker, G.T. and Mather, L.E., Wr. J. Anesth., 47, 213 (1975).

54. Veering, B.T., Wurm, A.G., van Kleef, J.W., et al, Anesth. Anala., 66, 589 (1987).

et al,

55.

Bunn, A.G., van Kleef, J.W., G l a d i n e s , M.P., Anesth. Anala. 66, 1104 (1987).

56.

E3unn, A.G., Vermeulen, N . P . , van Kleef, J.W., et al,

57.

Bunn, A.G., de Boer, A.G., van Kleef, J.W., et al, B i m Drua Dismsit., 2, 85 (1988)

Clh. pharmacokin.,

13, 191

(1987).

.

.

58. Mather, L.E., Long, G.J. and Thomas, J . , Clh. pharmacol. I .Ther u, 935 (1971). 59. 60.

Bunn, A.G., van Kleef, J.W., G l a d i n e s , M.P., et al, Anesthesiol., 3,191 (1983)

. Bunn, van Kleef, Jew., Venneul-, Anesthesiol., 69, 584 (1988). A.G.,

N.P., et al,

61. KUhnert, B.R., Zuspan, K.J., KUhnert, P.M., et al, Anesth. Anala., 66, 986 (1987). 62. Kbhnert, B.R., Zuspan, K . J . , KUhnert, P.M., et al, Anesth. Anala., 66, 407 (1987).

ANALYTICAL PROFILE OF CEFTAZIDIME

IVIohammad A. Abounassif Neelofur Abdul Aziz Mian* Mohammad Saleem Mian

Pharmaceutical Chemistry Department, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh-11451, Saudi Arabia.

*Clinical Laboratories Department, College of Applied Medical Science, King Saud University, P.O. Box 10219, Riyadh-11433, Saudi Arabia.

ANALYTICAL PROFILES OF DRUG VOLUME 19

SUBSTANCES

95

Copyright 0 1990 by Academic F’ress, Inc. All rights of repmduction in any form reserved.

MOHAMMAD A. ABOUNASSIF ETAL.

96

Contents

I,

Description 1.1

1.2

Nomenclature 1.1.1 Chemical Names 1.1.2 Generic Names Formulae 1.2.1

1.3 1.4

1.5 2.

1.2.2 1.2.3 Molecular Elemental Color and

Emp i r ic a l

S tr ii c tura1 (;AS Registry Number Weight c’ompositioii Appearance

Physical Properties 2.1 2.2

2.3

2.4 2.5 2.6 2.7

2.8 2.Y 2.1u

Melting Range Solubility Optical Rotation Action Stability plia PH Crystallization of Ceftazidime X-Ray Powder Diffraction Spectral properties 2 . 1 0 . 1 Ultraviolet spectrum 2.10.2 Infrared Spectrum. 2.10.3 Nuclear Magnetic Resonance Spectra

3,

Synthesis

4.

Metabolism

5.

Uses and Requirements

6,

Cautions and Adverse effects

CEFTAZIDIME

7.

8,

Yethods of. 4nalysls i,1 Olemental A-\nalysis / . 2 Colorimetric 7, : i Microbiological i,4 Chromntographlc 7.5 Thermal Behavlor References

97

MOHAMMAD A. ABOLJNASSIFETAL..

98

1.

D_escription 1.1

Nomenclake Chemical Nagis

1.1.1

(a) 1-[1(GH,7H))-i-(Z-Amino-4-thiazo~y~~~i~o~~~~amido]-Z-carboxy-8-oxo-s-thia-l-az~l~icyclol4.2.O~-oct-2-en-Y-ylJmet.hSllpyridinium hydroxide, inner s a l t . 7. (Z)-(0-(1-carboxy-1-methyl-ethylloxime). ( 1 , Z )

(b) (6H-7K)-7-[(Z)-2-(8-Aminothi~zol-4-yl)-2-~2carboxyprop-Z-oxyimino)acetamidoJ-~-(l-p~ri~ini~immethyl)-ceph-3-em-4-carboxylic acid inner salt. ( 2 ) (c) ItiR-[Ga, 7l~~~~I1-1-[[i-ll(~-amino-?-thiazolyl) [(l-carboxy-l-methylethosp)imino~acetyl~aminoi-8-carboxy-8-oxo-5-thia-l-~zabicyclol4.2.0loct.-~-ene-~yllmethyllpyridinium hydroxide, inner salt. ( 2 )

(d) 1-[ 1 / - l (2-Amino-4-thiazolyl)l [ (l-carhoxy-lmethylethoxy~iminoJa~~t~~llamino)-2-carboxy-~-o~~-5thia-l-azabicyclo[~.~.Oloct-~-~n-J-yllmeth~l~ pyridinium hydroxide, inner s a l t . ( 1 ) 1.1.2

__Generic -.Names I..

F o r t am. 1.2

Formulae 1.2.1

Eapi rical

1.2.2

Structural

CH 3 CH,+COOH

CEFl'AZDIME

99

CAS Hegistrg Number

1.2.3

172558-82-8 I a n h y d r o u s 178439-06-21 p e n t a h y d r a t e . Ceftazidime pentahydrate 1.16 g is approximately e q u i v a l e n t t o 1 g of a n h y d r o u s c e f t a z i d i m e . ( 3 )

1.3

Molecular Weight

1.4

Elemental Comwsitior! 2 1

C

38.33%;

S

11.74%.

1.5

H

4.UtjX;

N 1.5.Y8%:

0

20.~,U%;

Color and Appearance

White t o off w h i t e powder.

2.


Melting Range

Changes t o d a r k brown and decomposes a t 135 t o 137 C .

2.2

Solubility

The d r u g h a s t h e s o l u h i l i t i e s of .j m q / m l less t h a n 1 mg/ml i n a l c o h o l . ( 4 )

2.3

Optical Rotation 20

1oln 2.4

i n water and

=

t 24.5.. ( 2 )

Action

C e f t a z i d i m e h a s a b a c t e r i c i d a l actioii and hrnad s p e c t r u m activity but i n c r e a s e d a c t i v i t 1 a g a i n s t p s e u d o m o n a d s s p e c i e s I 11, Drug i s h i g h l y s t a b l e t o h y d r o l y s i s b y most I + - l a c t a m a s p s p r o d u c e d b v Gram-negat i v e and Gram-posit i v e bacl eria.

MOHAMMAD A. ABOUNASSJF ETAL.

2.5

Stability

Drug f o r i n j e c t i o n is e s s e n t i a l l y s t a b l e i n t h e d r y s t a t e a n d c a n be s t o r e d a t room t e m p e r a t u r e , b u t should be p r o t e c t e d from l i g h t , khen r e c o n s t i t u t e c l with Hz0 f o r i n j e c t i o n s loss of potency o c c u r s s l o w l y and it is recommended t h a t it s h o u l d be used w i t h i n 6 hours i f s t o r e d a t room t e m p e r a t u r e and 24 hours i f i n refrigerator. (31 R e c o n s t i t u t e d 1 g v i a l s of drug f o r i n , j e c t i o n added t o 50 m l m i n i b a g s of sodium c h l o r i d e i n j e c t i o n ( 0 . 9 % ) were found t o be s t a b l e f o r 97 days when s t o r e d a t ZO'C. A f r o z e n s h e l f l i f e of 42 days was s u g g e s t e d . t o allow f o r a r e f r i g e r a t i o n l i f e of 4 days followed by 2 4 h o u r s at room t.emperature. ( 5 ) 2.6

a&

Ceftazidime has pKa's of 1 . 9 , 2 , 7 and 4 . 1 . ( 6 )

Ceftazidime sodium s o l u t i o n s have a pH of 5-8 and are l i g h t y e l l o w t o amber i n c o l o r d e p e n d i n g on t.he d i l u e n t u s e d , c o n c e n t r a t i o n of t h e d r u g , and l e n g t h of storage. 2.8

Crystallization

of

Ceftaeidime

C r y s t a l s of c e f t a z i d i m e h a s been p r e p a r e d bv a~I.iusti n q an aqueous s o l i i t i o n 01 c e f t a z i d i m e from lot1 5.3-ti.5 t o 4.0-4.7 a t 5-15 r' uslrlg H c ' l or t l z P ( - h , lhus a s u s p e n s i n n of 2.1 g m of c e f t a z i d i m e i n 5 m l 1i1U wits cooled t o 3 C' aiid a d j u s t e d pH b . 9 w i t h 1.28 M NaOH, d i l u t e d with H z O t o 190 mg/ml, w h i c h was trcfi;ite~-l with 2 . 5 M H3W4 at 5 C t o 11it 1,4 and tlieri 4.2 t o ~ i 211 v gm of d r i e d crystals. 2.9

X-Hay Powder U i f k a c t i o n ( 8 )

T h e I - r a y d i f f r a c t i o n 1 < i t t e r n ok c e t t a z i d i m e was determine.! on H P h i l i p s X-ray d i t t r a c - t i o n s p e c t r o s o n i o m e t e r f i t t e d w i t h Pk 1730 q e n e r a t o r . R a d i a t i o n hias provided by a copper t a r g e t (r;u anode 2000 W , y = 1.5480 4 ) and high i n t e n s i t y x - r a y t u b e o p e r a t e d a t 4U h\. and 35 MA. 3 h e monochromator was a

~

CEFTAZIDIME

101

c u r v e d s i n g l e c r y s t a l o n e ( Pk 1 i 3 2 / 0 0 ) . Divergence s l i t a n d t h e r e c e i l i n g s l i t were 1 a n d 0 . : respectively. I'he s c a n n i n g s p e e d o t t h e griiiiometrr (PW 105O/kIl) u s e d was 0 . 0 2 - 2 tf per s e c o n d . 'Ihc. i n s t r u m e n t is combined w i t h P h i l i p s PM 821U p r i n t i n g recorder w i t h b o t h a n a l o g u e r e c o r d e r a n d d i g i t a l printer. The g o n i o m e t e r was a l i g n e d u s i n g s i l i c t i n sample b e f o r e use. The x-ray p a l t e r n o l c e f t a z i d i m e is p r e s e n t e d i n Fig. ( 1 1. 'I'he i n t r r p l a n r i e r di.itaiic P dA and r e l a t i v e i n t e n s i t y 1/10 a r e shown i n l a h l r ( 1 1 .

2.10

Spectral P r o p e r t i e s 5.10.1

Ultraviolet S p e c t r u m ( U V )

The u l t r a v i o l e t a b s o r p t i o n s p e c t r i i m of r e f t a z i d i m e i n 0 . 1 hi H2s0.1 h a s o b t a i n e d o n 4 0 5 4 L h U l i \ / \ i s s p e c t r o p h o t o m e t e r ( 8 ) . 1 he s p e c t r u m shown i n b J 4. ( Z ) e x h i b i t r d a maximum a t 2hO n m . l h ~s p e c t r a o f c e f t a z i d i m e showrd a maxiniuni a t 238 iini and L 5 7 tim 111 Hz0 and m e t h a n o l r e s p e c t i v e l y . 2.10.2

I n fr a r e d Suectrum

MOHAMMAD A. ABOUNASSIF hT AL.

102

45

40

35

30

25

20

15

10

5

Fig. 1: Characteristic principal lines of the X-Ray powder diffraction of ceftazidime.

R 7

EZSE'E

ESS'EZ

OGbZ'E 166Z'E

161'EZ FLfi'LZ

ESSO'E S6hl'E OL61.E

OBV'EE

BPb'9Z

L06'0E 018'61 bRS'6Z

5610'E

REI'LE

lf.66'7.

O6b' SE ELE'Sl

EZT'ZE

6b7.L'Z b98L'Z

SSI ' bZ

6989'7.

bIt'T1

IHI'PE

ZEZ9'Z

E6b'bE

1009'7

660'6Z S6U'61 1 TR ' 01 SOB'LI

RR9'9Z

L86'ET

ESE'SE

WES'Z

ET9'SE

60ZS'7.

IEGR'Z

IRUL'E

CZF'LZ

6969'h

PZB ' 98

STRb'E

610'67.

1TPt'F

29s * 5 2

LLR'ZR

URLU'E LSb6'E

EG6 ' 1 E

86UE'b 7CES'F

961'6t

GRZO'B LOET'b IZLI'f

SZO'L6 9EZ'EL

R89 ' 1s

EOP'LI

fim' L Z L

bEA9'6

ZtOt'G IGSF'S

BIh'EE

SIFL'F bS66.b

6LO'R

65 9

SSh'tt

9bE'EE U9FI'ZE

zci*az 9EE'UZ

LOG'LZ TSC'LZ ugn*iZ

066'92 16R'SZ GUS * sz

ELO'bZ

FRP'EZ RZ6'ZZ EES'ZZ

E9O'ZZ ZTS'TZ 96Z'IZ SZZ'OZ ZBS'6I ZS6'Rl

PIL'XI SSL'Ll LCO'Ll 9EZ'91

OEF 'GI OLL'PI OZ~'E~

wzo'nr

110'69

ss1.11

9rui-L firsiL'5

CLH'ZI

btLH'9

cjSI'E1

SELL'S tL66'S 919F.9 F4ZL'9

E06'BZ Sll'PZ 99C'EI L69'ES

600'LZ IPS'f'l. Fq9.9Z

no1

t 4 L n . 91

nLo.01

STS'? 96f'E ~.

1% C ' T l I I

Yi'

R 7

:1 a T q o l

€01

z0 -

c

y

h

l

-

0

m

0 0

o

0 0 -

104

0

0 0 0

8 E

0 0

* 0 aD

m

0

fn

0

0

*

m 0 hl

m

m

0 0

0

aD hl

0 W

hl

0 * hl

0

N

hl

0 0 N

0

b,"

0'

00

0 \D

0

d

105

0

h)

0

8

4 I

0 0 N

0 0

d 0 0

0 0

CT,

0

0

0 4

ca

c\1 rn

0 0

d 4

0 0 \D Fl

0 0

m A

0

0

0

h)

0 0

m

h)

0

0 0 M

0 0

m

M

0 0

0

d

MOHAMMAD A. ABOUNASSIF ETAL..

106

Freauency

cm-'

A s s i@nien t

,

3UOU-BtiUU

OH s t r e t c h i n e ,

1810

C'-S-C

16'iU

8t retcliinq of amide carboiiyl.

1450

C'-N

ti 00 -tloo

Adjacent hydrogen del'ormat ions. 2.10.3

NH2

(.'-H s t r e t c h .

stretch.

Nuclear Mamiet ic Resonance t33eLrrU

2.10.3.1

Proton Spectra ( W )

The PMR s p e c t r a of ceftazidime i n OMSO-dh was recorded on a Varian PT 8 O A , 80 MHz NMtl spectrometer u s i n g 'TMS as fin i n t e r n a l r e f e r e l i c e . ( F i g . 1 ) . T h e s p e c t r a l assignments a r e presented i n T a b l e ( 3 )

.

Table 3 :

PMR c h a r a c t e r i s t i c s of ceftazidime

Croup

s

Chemical shift 6 (ppm)

C-CH3

1.38

s

-C:H:i

1.7u

s

N-CHZ

5.(J2

d

-t4H

6.66

s

-CHZ

8.U8

m

-CH2

9-34 d

= singlet,

d = doublet,

m

= multiplet..

CERAZIDIME

107

f

16.25

0

Fig. 4: PMR spectrum of ceftazidime in DMSO-d6.

Fig. 5 :

"C-NMR complete decoupled spectrum of ce ftazidime.


108

The l J C hMH s p e c t r u m o f c e f t a z i d i m e i n 1)MSO u s i n g 'IMS as a n i n t e r n a l r e f e r e n c e is recorded on Jerrl r'X -1OU FT NMH S p e c t r o m e t e r ( Y ) and is p r e s e n t e d i n b i g , 1 5 ) . 2.1U.4

_-Mass gpectrur

The mass s p e c t r u m of c e f t a z i d i m e i s p r e s e n t e d i n k i g . ( 6 ) . 'rhi s was o b t a i n e d by e l e c t r o n impact 10111 z a t i o n on a Y i n n i g e n 3UU Mass S p e c t r o m e t e r by d i r e c t i n l e t p r o b e a t 270 f : , 'The e l e c t r o n e n e r g y was 7U e v . Ihe s p e c t r u m was s c a n n e d t o mass 55U a.m.u. The s p e c t r u m s h o w s a m o l e c u l a r i o n p e a k !+I a+ t m/e 5 4 7 w i t h a r e l a t i v e i n t e n s i t y o f 40%. 'I'he base peak a t 1 h Y w i t h a r e l a t i v e i n t e n s i t y of 100%. 3.

Synthesis

(10)

C e f t a z i d i m e is s y n t h e s i z e d by t h e r e a c t i o n of n i t r o u s a c i d w i t h e t h y l a c e t . o a c e t a t e t o p r o d u c e o x i m e . 'I'he oxime is n e x t c o n v e r t e d t o 2-aminot h i a z o l e by halogenat,ion w i t h s u l f u r y l c h l o r i d e followed by t h i o u r e a displacement. The amino group i s p r o t . e c t , e d by t h e t r i t y l amirie a n d t . h e n ether f o r m a t i o n w i t h e t h y l 2-bromo-2-methylpropionute q i v e s int.ermediatr. The s p o i i i f i c a t i o n t h e n f r e e s t h e carhoxy g r o u p f o r c o n d e n s a t ion w i t h t. b u t y l , 7 - a m i n o c e p h n l o s p o r i n a t e mediated by d i c r c l o h e x y l c a r b o d i i m i d e a n d l - h y d r o x y b e n z o t r i a z o l e . The s y n t h e s i s is c o m p l e t e d by r e m o v a l of t h e p r o t e c t i n g g r o u p s from t h e product formed w i t h t r i f l u o r o a c e t i c a c i d and d i s p l a c e m e n t . of t h e acet,oxyl moiety from ('-3 by t , r e a t m e n t w i t h p y r i d i n e arid sodiiim i o d i d e i n order to g i v e c e f t a z i d i m e .

f .-

-

I

a. 3

1

i

I

Fig. 6: The mass spectrum of ceftazidime.

MOHAMMAD A . ABOUNASSIF E T A L .

110

Scheme :

0 I1 CH3COCHgoEt

+

HNO,

NOH II + CH,COCCOOEt

Ethyl acetoacetate

S0Clz

I"

I

Oxime

NOH II

NH2 2 -Aminothiazole

I

I 0

0 f""H3

Q)

u

3cH

0

q C NHP tritylamine

COOEt Intermediate

2 z

Sponif i c a t ion

C0,- t-Bu

CEFIAZIDIME

4.

111

Metabolism

Ceftazidime is not absorbed from GI tract and must be given parenterally. 1M injection into the qluteus maximus o r vastus laterals, ceftazidime may be absorbed more slowly in women than in men. In women, peak serum concentration of the drug may be lower following 1M injection into the gluteus maximus than into the vastus laterals. ( 6 ) Ceftazidime is administered by injection as the sodium salt. Mean peak serum concentrat.ion of 1 7 and 39 pg/ml have been reported approximately one hour after intramuscular administration of the equivalent of 0 . 5 and 1 g of ceftazidime respectively. Five minutes after intravenous b o l u s in,jections of Hie equiralent of 0 . 5 , 1, arid 2 gm of ceftazidime, mean serum concentrations o f 4 5 , YU and 1 7 U pg/ml, respectively have been reyort.ed. l'he plasma eliminat.ion half l i r e of ceftazidime is about 1 . 8 - 2 . 2 h o u r s hut this is prolonged in t.he patients with severe renal failure and in neonates. It. is about 10-17% Ixnind to plasma proteins. ( 3 ) Ceftazidime is widely distributed in body tissues and fluids including boiie, synovial fluid, heart, b i l e , sputum and aqueous humor; therapeutic concentrat i o n s have been achieved in the cerebrospinal fluid when the meninges are inflamed, it diffuses across the placenta and is excreted in breast milk. ( 3 ) Plasma concentrations of crftazidime decline 111 biphasic manner. In adults w i t h normal renal and heptic function, the distribution half life ( t t a ) of ceftazidime is 0 . 1-0.6 hours and the elimination half life ( t g n ) is 1 , 4 to 2 hours. ( 6 ) Ceftazidime is not metahol i z e c l arid is excrel ed unchanged principally i n i.ir i n e b y plnmerular filtration. Following IM o r I L administration of a single 0 . 5 or 1 g dose of drug i n adults with iiormal renal function, 8c)-9U% of the dose is excreted in urine unclianged within 2 4 hours? approximately 5UX oi the dose is excreted within 2 hours after the dose. (ti)

MOHAMMAD A. ABOUNASSIP ETAL.

112

Serum clearance of ceftazidime average 98-122 m l / m i n in healthy adults. In geriatic patients 63-83 years of age with urinary tract infections, serum clearance of ceftazidime averaged 79 ml/min and the serum half life of a drug averaged 2.9 hours. In patients with cystic fibrosis, the serum clearance of ceftazidime ranges from 142-316 ml/min per 1.73 M L , the serum halt life of the drug in these patients, however, ranges from 1 - 2 . 2 hours and generally within the same ranee as that for healthy individuals. ( 6 ) The serum half life of drug is longer in neonates than in older children and adults. Serum concentration of drug are higher and the serum half life o f drug is prolonged in patients with impaired renal function. The serum half life of the druq; only slightly prolonged in patients with impaired hepatir function and accumulation of the drug does not generally occur in those patients unless renal function is also impaired, Ceftazidime is readily removed by hemodialysis. drug is also removed by peritoneal dialysis. ( 6 ) 5.

The

Usesand Hequirements Ceftazidime is t hird-generat ion cephalosporin antibiotic with enhanced activity against Pseudomonas aeruginosa. It is used in the treatment of susceptible infections including respirat,ory-tract infections such as pneumonia and lung infections in patients with cystic fibrosis-urinary t r a c t infections, skin and soft tissue infections, bone and joint. infections, peritonitis and other abdominal infections, septicaemia and meningitis. It 1s often used alone but can be used i n assnciaticin with an amiiioglycoside o r vancomvcin 111 patients w i t h severe neutropenia, or if infection with Bacteraides fragilis is suspected, it may be used in association Kith an antibiotic active against R n a e r o b e s such as clindamycin or metronidazole. The drug should generally be administered separately. ( 3 ) Ceftazidime is used for the treatment of gynecologic infections (including endometritis, pelvic cellulitis. and other infections of female genital tract). ( 6 )

CEFTAZIDlME

113

C e f t a z i d i m e i s a v a i l a b J e as t h e p e n t a h y d r a t e b u t i t I S f o r m u l a t e d w i t h sodium c a r b o n a t e t o form t h e sodium s a l t . i n s o l u t i o n , Doses a r e e x p r e s s e d i n terms of anhydrous ceftazidime. I t i s a d m i n i s t e r e d by d e e p i n t r a m u s c u l a r i n j e c t i o n , slow i n t r a v e n o u s i n j e c t i o n , o r i n t r a v e n o u s i n f u s i o n i n doses of 1-ti g d a i l y i n d i v i d e d doses e v e r y 8-12 hours. The h i g h e r d o s e s are u s e d i n s e v e r e i n f e c t i o n s e s p e c i a l l y i n immunocompromised p a t i e n t s . In patients with cystic f i b r o s i s who have pseudomonal l u n g i n f e c t , i o n s , h i g h d o s e s of 1OU-150 m g p e r kg body w e i g h t d a i l y i n 3 d i v i d e d doses u p t o 9 g d a i l y h a s been g i v e n t o a d u l t s wit.h normal r e n a l f u n c t i o n I f p a i n is c o n s i d e r e d a problem w i t h I \ u s e , d r u g may b e r e c o n s t . i t u t , e d J c i t h l i g n o c a i n e h y d r o c h l o r i d e 0.5% o r 1% i n j e c t . i o n . ( 3 )

.

30-100 mg p e r kg i n 2 o r 3 d i v i d e d closes of d r u g a r e usually g i v e n t o t h e c h i l d r e n and ma! i n c r e a s e u p t o 150 mg p e r kg d a i l y t o a maxinium o f ti s d a i l y may b e given i n 3 divided doses. N e o n a t e s and i n f a i i t s u p t o 2 months o l d have been q i v e n 25-60 m g p e r kg d a i l y i n 2 d i v i d e d doses. 1 3 ) 6.

Caution8 and Adverse Effects A d v e r s e e f f e c t s r e p o r t e d w i t h c e l ' t a z i d i m e arrt 6 1 0 1 1 I:+r t o t . h o s e r e p o r t e d w i t h o t h e r r.-ephalospr,rins. C e f t a z i d i m e i s g e n e r a l l y well t o l e r a t e d , a d \ . e r s r e f f e c t s h a v e b e e n r e p o r t e d i n a b o u t 9% o f p i i t i e n t s r e c e i v i n g t h e drug and have been r e q u i r e d d i s c o n t i n u a n c e i n about. 2% of p a t i e n t s . ( 6 1

Lo s 1 n o p h i 1i a ? t h r o 01 bo c y t o s 1s ? t ran s i e n t 1e u kopen i a, n e u t o p e n i a , t h r om ho c y t o p e n i a a n d 1y m p h o c y t r) s 1 s may occur i n 2-7% of t h e p a t i e n t s r e c e i v i n g c e f t a z i d i m e . (ti) A d v e r s e GI e f f e c t s , including diarrhea. nausea, v o m i t i n g , abdominal p a i n and a m e t a l l i c t a s t e have been r e p o r t e d i n 2% of t h e p a t i e n t s . ( t i ) Hash ( m a c u l o p a p u l a r o r e r y t h e m a t o u s ) p u r i t u s , u r t i c a r i a , f e v e r and a d v e r s e local r p a c t i o n s i n c l u d i l i < ( p h l e b i t i s arid p a i n o r i n f l a m m a t i o n a t t h e i n f e c t i o n s i t e h a v e b e e n r e p o r t e d i n l e s s t h a n 9% of t h e patients receiving ceftazidime.

MOHAMMAD A. ABOUNASSIF ETAL..

114

T r a n s i e n t i n c r e a s e i n serum c o n c e n t r a t i o n s of S W Y , S b p t , A 1k a 1i n e p hos p h a t ase , L L)H a n d / y - g l u t xmlr 1t r a n s f e r a s e ( y - g l u t a m y l t r a n s p e p t i d a s e , MA. G G I Y ) , b i l i r u b i n , bun and serum c r e a t i n i n e have been r e p o r t e d 111 1-9% of t h e p a t i e l i t s , receiving ceftazidime in a p p r o p r i a t e l y l a r g e d o s e s , mag c a u s e s e i z u r e s , e s p e c i a l l y i n p a t i e n t s k i t h r e n a l impairment. l'lic d r u s s h o u l d be c l i s c o n t i i i u e d p r o m p t 12: i f s e i z u r e s o c c u r ; a n t i e o n v u l s a n t t h e r a p y may be a d n i i n i s t e r 4 i t i n d i c a t e d . I f a c u t e overdosage of c e f t a z i d i m e o c c u r s , h e n o d i a l y s i s may b e u s e d t o m h a n c e d e l i m i n a t i o n &>t t h e drug. (6)

I t h a s been reported t.ha1- c e f t a z i d i m e does n o t c a u s e d e c r e a s e d a c t i v i t y when i n c u b a t e d i n s o l u t i n r i w 1 t h g e n t a m y c i n o r t o b r a m y c i n a t 37 ' C [ 1 1 , 1 2 1 . However, t h e m a n u f a c t u r e r s recommended t h a t c e f t a z i d i m e , 1i k e mast o t h e r Ij-lactam a n t , i b i o t i c s , s h o u l d n o t b e niixed w i t h a n a m i n o g l y c o s i d e i n t h e same g i v i n g set o r s y r i n g e b e c a u s e of p o t e n t i a l i n t e r a c t i o n . c ' a i r n s and Hobert.son ( 1 3 ) r e p o r t e d t h e p h y s i c a l i n c o m p a t i b i l i t y between c e f t a z i d i m e and vancomycin. 7.

Methods

7.1

of Analysis Elemental Analysis

The e l e m e n t a l a n a l y s i s of c e f t a z i d i m e as r e p o r t e d is: C ' 2 z H z 2 N 6 0 7 S z = 546.90 Element

c

7.2

(

21

3 'fheo r e t.i ca 1 48.93%

H

4,06%

N

15.38%

0

20.50%

S

11.74%

Colorimetric Method ( 1 4 )

A c o l o r i m e t r i c m e t h o d f o r t h e d e t e r m i n a t i o n of c e f t a z i d i m e h a s been d e v e l o p e d which is based o n

CEFTAZIDIME

115

frlrmation o f d i a z o p r c i d u r t s w i t h h a N 0 2 i i i a c i d i c medium. I h e c n l o r i a b s n r h a n c e I was measiri.ed a t nl)U n m . A linear r e l a t i o n b e t w e m t h e c o l o r i n t e n s i t $ awl d r u g c o n t e n t was observed i n t h e c o n c e n t ratiori r'aritle 12.5-ZU0

1.3

pg/ml.

Microbiological Methods

(a) A s e n s i t i v e method i 1 5 ) is d e s c r i b e d i o r the d e t e r m i n a t i o r i of c e f t a z i d i m e i l l b i o l o g i c a l f l u i d s u s i n g P r o t e u s m o r g a n i i N C l C Z 3 5 as t h e t e s t o r g a n i s m . l'he o r g a n i s m i s c u l t u r e d o v e r n i g h t on n u t r i e n t agar s l o p e s a t 9 1 , t h e g r o w t h is t h e n washed o f f i n 5 ml p h o s p h a t e b u f f e r a t pH i . O ? arid t h e s u s p e n s i o n i s d i l u t e d lO-folcl t o c v n t . a i n a b o u t 10' c e l l s / m l a n d a d d e d i n an amount e q u a l t o 1%t o t h e m o l t e n a g a r h e l d Aboiit 1 2 . 5 m l o f i n o c u l a t e d in Petri dishes a t SU.. medium is p o u r e d 1 n t . o 9-cm p l a t e s ( l a r g e 1 2 i n c h e s p l a t e s c a n a l s o be u s e d ) . Holes are punched in t h e a g a r f o r s t a n d a r d and Lest s o l u t i o n s . A f t e r 18 h o u r s i n c u b a t i o n a t 37 ' C , zone d i m e n s i o n a r e measured ancl ceftazidime concentrations i n t h e samples are e s t i m a t e d from a s t a n d a r d c u r v e . (bj M i c h a e l e t a l . ( l b ) a n a l p s e d c e f t , a z i d i m e 111 serum a n d body f l u i d s b y Large-p1at.e a g a r d i f f u s i o n t e c h n i q u e u s i n g s t a n d a r d solilt i o n s oi t h e d r u g made u p i n human serum. Serum samples were sssayed a g a i n s t s t a n d a r d s made up i n l U 0 X serum arid each t.est serum s a m p l e a n d s t a n d a r d ( 2 5 p l ) was i n o c u l a t e d i n t o Nhatman A.l p a p e r d i s k s . Standard s o l u t i o n s f o r a s s a y i n g b l i s t e r f l u i d and c a n t h a r i c l i n b l i s t r r f l u i d were p r e p a r e d w i t h 50 and '10% serum r e s p e c t i v e l y made u p i n p h o s p h a t e b u f f e r ( p l l 0. Blister f l u i d a s p i r a t e s a n d s t a n d a r d ( 5 p l ) were i n o c u l a t e d o n t o ti-mm d i s k punched from Whatman no. 54 f i l t e r p a p e r . C o t t o n t h r e a d s were r e m o v e d a n d immediate1:t r a n s f e r r e d i n t o p r ew e i ghed bo t t.1e s w h i c h were t h e n weighed. l'he t h r e a d l e n g t h s were m e a s u r e d , and t h e amount of f l u i d t a k e n u p per c e n t i m e t e r of l e n g t h was calculated. l'he t h r e a d s were t h e n c u t i n t o two 1-cni lengths for assay. S t a n d a r d s f o r t h e t h r e a d s were p r e p a r e d by i m p r e g n a t i n g 1-cm 1engt.hs of d r y t h r e a d w i t h 5 p1 of known c o n c . o f a n t i b i o t i c d i s s o l v e d in 50% serum.

MOHAMMAD A. ABOUNASSIF ET AL.

116

D i s k s impregnated w i t h serum and b l i s t e r t l u i d s were p l a t e d i n t o t h e unpuriched s u r f a c e of l a r g e a s s a y p l a t e s . 'I'he threads were inserted i n t o .+mm diameter w e l l s c u t i n t o a g a r p l a t e s , and 5 p l o t s a l i n e was added t o each well t o a s s i s t uniform e l u t i o n of the antibiotic. Serum conc, i n excess of 5 U pg/ml were assayed by i i s i n q Bacillus s u b t i l i s 1YU4 seeded i n t o Oxoid A n t i b i o t i c assay medium No. 2 w i t h J g oi sodium c i t r a t e added per l i t r e . c'oncs o i drug i n b l i s t e r a n d thread f l u i d s and serum concentrations of l e s s t h a n J U l i g / l i t r e Kere assayed by u s i n g proteus morganii 2 3 5 . I n these assays the p l a t e s consisted of a base l a y e r of n u t r i e n t agar and a top layer of Uxoid l s o s e n s i t e s t agar i n t o which the orgallism was seeded. A l l assay p l a t e s were incubated o v e r n i g h t a t J i t.', For the tlirends, the assay results were corrected f o r the volume of f l u i d absorbed ( 4 t o J til/cni) before the

a n t i b i o t i c concentrations were calculated

1.4

mromatorfraphic Methods performanc_e Liquid 6hm.matoRraphj

Some of the rapid and s e n s i t i v e hiqh-pressure l i r l i i i d chromatography ( H P L C ) procedures f o r t h e y u a n t i t a t ive a n a l y s i s of ceftazidime a r e summarised i n Table ( 41 ,

7.5

Thermal Behavior

A d i f f e r e n t i a l scanning colorimetry curve was obtained F i g ( 7 ) on a P e r k i n - E l m e r L)SC'-BC d i f f e r e n t i a l

calorimeter, Nitrogen was used a s t h e purge g a s . Scan was performed a t t h e r a t e o f 25 C / m i n from 6O'-Y8U'C. 'The L)YC curve r e v e a l e d an endothermLc melting peak (Max. 132.71'C).

Ceft az idime MN RATE#

Fig. 7:

The differentical scanning calorimetric (DSC) thermal curve of ceftazidime.

Table 4: Summary of HPLC conditions f o r the determination of ceftazidime.

Column

Mobile phase

( 3 0 cm h 3 . Y mm of ji

Bondapak

Acetic acid:HzO: acetonitrile, pH

Flow rate 2 ml/min

Sample Serum. urine ('SF or peri-

Detect ion

Ref.

2 5 4 nm.

IS

255 nm

18

tonial fluid.

4.0.

(1U p). Cib

-

( 3 0 cm S 3 . 9 m m ) of p kndnpak CIR (10

pm) and a

Phosphate b u f f c r ipH 6.5): methanol 31:Y f o r serum 22:s for urine.

1 . 2 ml/min

f o r serum

Scrim or urine.

2.0 ml/min for iirine.

guard column of li Eondpali c i s of ( 3 7 to 50 pm). ( 1 0 cm .ri 5 m m ) of Hypersil ODS (pm)

0.05 M-NHJ HZ !Xh

.

containing 7% of acetonitri le and 0 . 1 % of formic acid.

1 ml/min.

Serum o r plasma

__

_ _ _ _ _ _ _ _ _ _ _ _ ^ _ _ _ _ _ ^ _ _

Continued

/...

Continued ( l a b l e 4 1

(‘olumn

...

Mobile p h a s e

blow r a t e

Sample

Detect i o n

Kef ,

____ Micropak MCHlU

ZU% m e t h a n o l i n 5U mM-NH-r H i P o 4

that in l l i ym i n HC’IOJ.

1 ml/min.

Blood o r

urine

2 3 1 nm

2 (1


120

8.

1,

References "The Merck I n d e x " , I n c . , Hahway, N . J . ,

p . 1913, Merck and Co., 1983.

1 0 t h ed. U.S.A.

2,

Annual Urug Data R e p o r t , Vol. 4, p . 41-45 I.R. P r o u s , S . A . P r o v e n z a , 383-38i B a r c e l o n a 25, S p a i n (1982).

3.

" M a r t i n d a l e " The E x t r a p h a r m a c o p e i a " 2 9 t h ed. Eds. E, b'. Reynolds and h a t h l e e n t'arfit t , p. 162. 'The P h a r m a c e u t i c a l Press, London, 1Y8Y.

4.

"Drug I n f o r m a t i o n " 88. American S o c i e t y of Ilospi t a l P h a r m a c i s t s . I n c . 4630 Montgomery Avenue-Uethesda M D 20814,

5.

A . F . Brown e t a l . , B r . J. P a r e n t l ' h e r . , 6 , 13, 1985.

6,

"Drug i n f o r m a t i o n " 8Y. American S o c i e t y nf H o s p i t a l P h a r m a c i s t s , I n c . 1630 Montgomery .ivenue-Bethesdn MI! 20814.

7.

Chemical . A b s t r a c t s ,

8.

Mohammad Saleem Mian, C o l l e g e of' Pharmacy, k i n a Saud University, Riyadh, Saudi Arabia, Unpublished d a t a

105,

226188r, 1986.

1990.

9.

N e e l o t u r Abdul A z i z Mian, C o l l e g e o f A p p l i e d Meclicnl S c i e n c e s , k i n g Saiid U n i v e r s i t y , U n p u b l i s h e d m n t e r i a l , 1990.

10.

"'l'he O r g a n i c C h e m i s t r y nf Uruq S y n t h e s i s " UaiIiel L e d n i c e r a n d Lester A . Y i t s c h e i , bol, 1 1 1 , p . 2 1 1 , J o h n W i l e p and Sons, X e w l o r k .

11.

N,

12.

'T.S.J. E l l i o t e t a l . , 4680, 198ti.

13.

C a i r n s C'.J. ( 1987 1 .

14.

Uri, J . V . ; J a i n , '1.L'. i t e c e n t Adv. C h e m o t h e r . , P r o c . l n t . Congr. C h e m o t h e r . , 1-1 ( S e c . 1 ) 2 4 5 - 2 4 6 , 1983.

and J .

,4ntimicrol), Chemother,,

ttobertsori,

Pharni. , . J

1_,

537

CEFTAZIDIME

15. 16.

121

T h o r n t o n , J . E . , JL A n t i m i c r o h . C h e m o t h e r . , 8 ( S u p p l . H I , 2 2 5 - 2 2 6 , 1Y81. U. M i c h a e l R i g a n , B r e n d a H o d g e s , G e o r g e R.S. ~ n d S t a u r t M . H . A n t i m i c r o b i a l A g e n t s &nA C h e m o t h e r a p y , 2 2 ( 6 ) , YY5-9Y8, l Y 8 2 .

17.

Hwang, P . T . H . , Urexler, P.G., M e y e r , M . C . , C h r o m a t o g r . , I ( 5 ) 979-987, 1984.

18.

L e e d e r , J . S t e v e n ; S p i n o , M i c h a e l ; 'l'esoro, Angelo, M . , MacLeod, S t u a r t M . , A n t i m i c r o b i a l A g e n t s Chemother. 2 4 ( 5 ) , 720-4, 1983.

1Y.

A y r t o n , J . , J- A n t i m i c r o b _ , C h e m o t h e r . U ( S u p p 1 . U ) , 227-31,

20

J-

1981.

Myers, C.M., Ulumer, J.L. Antimicrob. Chemother., ( 3 1 , 333-346, 1983.

&_gents

DICLOFENAC SODIUM Christianah M. Adeyeye and Pui-Kai Li Department of Pharmaceutical Chemistry and Pharmaceutics School of Pharmacy, Duquesne University Pittsburgh, Pennsylvania 15282

1 Description 1.1 Introduction 1.2 Appearance, Color, Odor 1.3 Formula, Name, Molecular Weight 2 Physical Properties 2.1 Ultraviolet Spectrum 2.2 Mass Spectrum 2.3 Nitrogen-15 Nuclear Magnetic Resonance Spectrum 2.4 Nuclear Magnetic Resonance Spectrum 2.5 Crystal Properties 2.6 Differential Scanning Calorimetry 2.7 X-Ray Diffraction 2.8 Solubility 2.9 pKa and Partition Coefficient 3 Synthesis 4 Stability 5 Pharmacology 6 Pharmacokinetics, Metabolism and Activity 7 Toxicity Studies 8 Analytical Methods 8.1 Gas-Liquid Chromatography 8.2 Thin Layer Chromatography 8.3 High Performance Liquid Chromatography 8.4 Spectrophotometric Methods 8.5 Nuclear Magnetic Resonance Spectroscopy 8.6 Colorimetric Methods 8.7 Gas Chromatography- Mass Spectrometry ANALYTICAL PROFILES OF DRUG SUBSTANCES VOLUME 19

123

Copyright 0 1990 by Academic Press, lnc. All rights of reproductionin any form reserved

CHRISTIANAH M.ADEYEYE AND PUI-KAI LI

124

1 Description

Svnonvms: Voltaren, Voltarol, Voldal, Voveran, Orthophen

Diclofenac sodium is a synthetic, nonsteroidal anti-inflammatory, and analgesic compound

w

1.2

w

Formula

Formula Weight 1 ' 4H1 O C ' 2 q N a

318.13

Diclofenac sodium is also described by the following chemical names: 1) 2) 3)

2-[(2,6-Dichlorophenyl)amino] benzeneacetic acid monosodium salt [0-(2,6-dichloroanilino)phenyl] acetic acid sodium salt sodium[0-[(2,6-dichlorophenyl)amino]phenyl] acetate

Diclofenac sodium is an odorless, white to off-white crystalline, slightly hygroscopic powder.

125

DICLOFENAC SODIUM

Pr

2

m

2.1 The ultraviolet spectra of diclofenac sodium (batch 46694), in two solvents, methanol and phosphate buffer pH 7.2, were obtained with IBM UV/visible 9420/9430 spectrophotometer in our laboratory. The spectra depicted characteristic aromatic absorption (Figure 1). The wavelengths of maximum absorption for the two solvents are 283 and 276 nm and the molar absorptivities E~~~ and^^,^, are 1.05 x 105and 1.01 x 1O 5 liter/mole-cm respectively.

ABSORBANCE

Figure 1 Ultraviolet Absorption Spectra of diclofenac sodium in methanol (i). and aqueous phosphate buffer (pH 7.2), (ii). b=lcm c = 7.86 x 10-6hA


126

2.2 The mass spectrum of diclofenac sodium was obtained with a ShimadzuLKB 9000 gas chromatograph-mass spectrometer and a Shimadzu 9060s multiple-ion-detector peak matcher were used. Diclofenac and 4’methoxydiclofenac (internal standard) were first converted to their respective indolinone derivatives. The electron-impact mass spectra (20eV) of indolinone derivatives of diclofenac and 4’-methoxydiclofenac are shown in Figure 2 (1 ). a)

2771M‘)

c L

c

b)

Figure 2 Electron - Impact mass spectra (20eV) of indolinone derivatives of a). diclofenac; b). 4’-methoxydiclofenac

2.3 m - 1 5 N

P

The 15N NMR of diclofenac sodium was measured in 20% solution of hexadeuteriodimethyl sulfoxide (DMSO-d,). The Chemical shift of 15Nof diclofenac sodium was-294.4 ( 2 ).

DICLOFENAC SODIUM 2.4

127

~

The 'H NMR of diclofenac sodium was recorded in deuterated methanol(d,) with sodium acetate as internal standard and using a Varian T60-A NMR spectrometer ( 3 ).The spectral assignments are presented in Table 1.

for

3.62

singlet

2

6 -7.5

multiplet

7

-CH,aromatic protons

We also recorded the 'H NMR spectrum of diclofenac sodium with an IBM AF/250 spectrometer in the pulse mode using deuterated methanol as the solvent. The spectral assignments is similar to the spectrum reported by F a t t a h a d The methylene protons appears as singlet with a chemical shift of 3.53. The chemical shifts of the aromatic protons are 6.24-7.28 and exhibits as multiplet. The spectrum is presented in Figure 3. 2.5 The crystal strucutre of the tetrahydrate of diclofenac sodium was determined by Reck et al. The compound crystallized in the monoclinic space group p2Jm with a=9.464(2), b=39.405(7), c=9.972(3) A and j3=90.72( 2)'. The unit cell contained two symmetry independent formula units (Cl,H,,CI,N0,)'Na+.3.94 H,O ( 4 ). 2.6 The differential scanning calorimetry (DSC) of diclofenac sodium was done with a Dupont 10908 thermal anlyzer at 20"C/min in static air (Figure 4). The analysis shows an exotherm at 280" C,followed by an endotherm. This result is indicative of melting and decomposition. The normal melting point range of the drug is 283-285" C.

e

N

m

Figure 3.

’H

NMR of diclofenac sodium

c120 : 180: 2ao: 240 : : : :380 :400: 440: 480 :: 520 : : :: I : : : : : : 280 320 5w Temperatwo P C )

Figure 4

DSC curve of Diclofenac sodium

W o n t log0

CHRISTIANAH M. ADEYEYE AND PUI-KAI LI

130

2.7

X

--

X -Ray structure analysis of diclofenac sodium showed that the two aromatic rings were twisted in relation to each other, the angle of torsion being 69' and the hydrogen bond 8 = 2x10-I nm. The two chlorine atoms substituted into the phenyl ring are responsible for the maximum twisting of the ring. The relative steric arrangement of the aromatic rings is known to influence receptor interaction of some non-steroidal antiinflammatory drugs including diclofenac ( 5,6 ).

2.8

..

The equilibrium solubility performed in various solvents at the indicated temperature (RT) are shown in Table II.

Solvent Deionized Water (PH 5.2)

RT

Methanol

RT

Acetone

RT

Acetonitrile

RT

Cyclohexane

RT

pH 1.1 (HCI)

RT

pH 7.2 phosphate buffer

RT

2.9

6

..

..

P a m Coefflclent

The pka of diclofenac sodium in water is 4 and the partition coefficient in n-octanol/aqueous buffer pH is 13.4 ( 7 ).

131

DICLOFENAC SODIUM

3.1 -of

Diclofenac Sodium

Synthetic procedures of diclofenac sodium have been described (8-12). The synthetic pathway by T a m u r a a d i s presented in Figure 5 ( 8 ). The a-(met hylt hio)acetanilide 1was obtained by N-acylation of N-phenyl2,6- dichloroaniline 1,The product L w a s oxidized with m-chloroperbenzoic acid (m-CPBA) or hydrogen peroxide (H2q) to give a(methylsulfinyl) acetanilide 5 Cyclization of 9to form product B w a s carried out by heating9 in benzene with p-toluenesulfonic acid (pTsOH). An alternate route through chlorination of 2 with N-chlorosuccinimide (NCS) in carbon tetrachloride (CCI,) gave l a n d subsequent cyclization of &with stannic chloride (SnCI,) yielded L Desulfurization of 5 with Raney Nickel (Ra-Ni) or Zinc dust - acetic acid (Zn - AcOH) obtained the oxindole L Hydrolysis of &with sodium hydroxide gave diclofenac sodium

L

3.2

S v n W s of -

L14

The synthesis of 14C labelled diclofenac sodium was achieved in 22% overall yield (13 ). The synthetic scheme is presented in Figure 6. It began with the preparation of 14C labelled (o-iodophenyl) acetonitrile P by the substitution of (o-chloromethy1)iodobenzene l w i t h [14C]KCNin mixture of 18 crown-6 in acetonitrile (14 ). The cyan0 group OfPwas converted to carboxylic acid 9through acid hydrolysis in 18N H 2 S 4. Esterification of the acid in MeOH-CH,CI,

afforded the methyl ester&

Coupling of the ester with 2,4-dichloroaniline using cuprous iodide (Cul)-potassium carbonate ( K 2 q ) yielded the diphenylamine 5 Base hydrolysis of the ester group of 5 t o acid& followed by reacting the acid with equimolar of sodium hydroxide in water obtained the final product [ 14C]diclofenac sodiumz

Diclofenac sodium tablets film coated with polymers like acrylate hydroxypropylcellulose were reported to be stable after storage for one week at 30°C in 80% relative humidity (15 ). Suppository formulation was also analyzed for stability using thin layer chromatography and ultraviolet spectroscopy. The formulation was stable for 24 months at room temperature (16 ). Stability in biological fluid (serum) was determined and the results demonstratedthat diclofenac sodium can be frozen for at least two weeks without degradation ( 17 ).


132

2

1

3

1

NCS

4

Ra-Ni

5

OT

5-

Zn-ACOH

6

Figure 5. Synthesis of diclofenac sodium

7

DICLOFENAC SODIUM

133

aWfl18 crorm-6

I

+

H&CN

["CIKCN

acetonitrile

1

2

ub"

U

5

7

Figure 6. Synthesis of f4C] diclofenac sodium

U


134

5.1 Diclofenac sodium is a potent anti-inflammatory agent, the effects of which have been demonstrated in carrageenan and kaolin paw oedema models of rats with adjuvant arthritis between18 and 21 days following the injection of Freund’s adjuvant ( 18 ). The ED& many times lower than most anti-inflammatory NSAID’s and at least half that of indomethacin and naproxen. 5.2 inhibition of P

r

l

The drug is among the most effective inhibitors of PGE synthetase, acting at a concentration of 1.6 pmol/L (19 ). It markedly inhibits platelet aggregation in rats (20 ). Jobin and Gagnon ( 21 ) also studied inhibition of ADP and collagen- induced aggregation of human platelets by diclofenac sodium and found it to be a potent and partial inhibitors respectively. 5.3

Anti-pvretic Fffe-

Following interperitoneal injection of various irritants (p-benzoquinone and aceticacid) to mice and rats respectively, diclofenac was found to have an analgesic effect in the writhing syndrome, an effect much higher than other NSAlDs tested. The anti-pyretic activity was also been shown in with yeast-induced febrile rats (18 ).

. .

6 6.1

. .e c

o

n

c

m Fxcratiqn

Voltaren is completely absorbed from the gastrointestinal tract after oral administration. The half-life of Voltaren is approximately two hours, with mean peak plasma levels of approximately 0.5 pg/ml and 1.O pg/ml occurring 2-3 hours after single doses of 25 mg and 50 mg of enteric coated tablets, respectively; mean peak plasma levels of 1.9 pg/ml are reached two hours after a single dose of 75 mg ( 22 ). Four hours after dosing the levels still detectable in the plasma are equivalent to about 10% of the maximum concentrations. Rectal administration of diclofenac sodium suppositories produces rapid peak plasma concentration at a rate and level of the same order as oral administration of the drug in solution. In rats and dogs, majority of the drug is found in the faeces, indicative of biliary excretion, whereas in rhesus monkeys 76% is excreted via the kidneys. In man renal excretion is greater than biliary excretion ( 23 ).

DICLOFENAC SODIUM

6.2 -vial

135

-F

Voltaren penetrates the synovial membrane and diffuses into the synovial fluid. From 4 to 24 hours after dosing, synovial levels of Voltaren are higher than the corresponding plasma levels ( 24 ). 6.3

. . .

Following rapid absorption, the drug is widely distributed with highest concentrations in the elimination organs (liver and kidney) and in the blood (22 ).

..

6:4

and A c t i v u

In man and monkeys, the metabolic change is hydroxylation , whereas in rats and dogs, the major metabolites are formed by direct conjugation, -Figure 7 - ( 22).

R3aCH2-H Metabolite

c'w NH

R'

R2

R,

R2

R3

I

OH

H

H

II

H

H

OH

Ill

OH

H

OH

IV

H

OH

H

Metabolites I, the 4-hydroxy derivative is the main metabolite in man. The metabolite I and IV reduce paw oedema and inhibit prostaglandin synthetase but all are at least 30 X less effective in the oedema test than diclofenac sodium on a dose/effect basis. The effects of metabolites II and Ill are produced only by high dosage and are not relevant. Metabolite I is about 6x more active than aspirin in the kaolin oedema test and also effective in rat adjuvant arthritis, though diclofenac itself is 40x more potent. All four have moderate analgesic activity in the writhing test but only metabolite I has an antipyretic effect. In acute toxicity studies, metabolite I has an LD, similar to diclofenac, the others (11, Ill, IV) having much higher levels (22). A new metabolite, 3'-hydroxy- 4'methoxy diclofenac has been identified, however, the metabolite does not significantly contribute to the therapeutics effect of the drug (25 ).


136

UIH

u7

ooc

.*

a-=rk

N

*

-.

P X O *

w

*

*rbt

*.

wcpl

m

mu

.

.

Figure 7. Metabolites oi diclofenac sodium and thelr metabolic pathways.

DICLOFENAC SODIUM

137

. . .

6:5

Using 4C-labelled drug and equilibrium dialysis, diclofenac is reported to be bound to human serum to the extent of 99.7%, of which not less than 99-99.4% is bound to serum albumin fraction. It does not modify the binding of warfarin acenocoumarol, prednisone and salicylic acid to proteins (22). 6:6 Concomittant administration of single oral doses of aspirin 6OOmg/kg and diclofenac sodium (50mg), causes a reduction in the area under the curve (AUC) of the diclofenac plasma profile ( 26 ). This was confirmed by Ciba- Geigy Ltd ( 27 ). Further studies in rat by Ciba Geigy (28 ) showed that proportion of unbound diclofenac increased with salicylate dosage and that the total (bound plus unbound) diclofenac in the plasma increased while the excretion of the drug and metabolites increased in the bile. Rosak and Schoffling (29 ); and Chlud (30 ) reported that insulin blood sugar and plasma tolbutamide levels were not affected by diclofenac sodium. Studies also showed that diclofenac sodium do not interact significantly with oral anticoagulant like acenocoumarol (31 ).

Pharmacokinetic studies carried out by Willis and Kendall (32 ), in young females (18 to 21 years) and elderly females (62 to 78 years) dosed with 50 mg of diclofenac sodium revealed that individuals mean curves and statistical analysis of drug handling in the two groups was similar. The amount of free drug excretion appeared greater in the younger group but the differences were not significant. Ciba Geigy Basle ( 33 ) compared the AUCs from a single dose of 50mg and repeated doses of 2 X 50 mg/day for 4 weeks in younger and older subjects and reported that differences between the groups were not statistically significant. In neither group did the bioavailability change over the period studied. 7:O

..

The major side effects of NSAlDs are gastric irritation and ulceration, due to inhibition of cyclooxygenase. Cyclooxygenase, PGE2 has a cytoprotective effect on the gastric mucosa by inhibiting gastric acid secretion and by helping to maintain the gastric mucosa barrier (34 ). I n acute toxicity studies diclofenac sodium was found to cause gastric lesions in a lower dose (12 mg/kg) compared to NSAlDs such as phenylbutazone ,

CHRISTIANAH M. ADEYEYE AND PUI-KAILI

138

oxyphenbutatozone 620mg/kg. Chronic toxicity studies over a period of 26 weeks (in doses of 5, 15,75 mg/kl) in rhesus monkeys produced evidence of gastrointestinal lesions only at the highest 75 mg dose ( 23 ).

8.1 Gas - liquid chromatography has been used to analyze diclofenac sodium and its metabolites ( 35-40 ). The column conditions are presented in Table Ill. Because of its high sensitivity, electron capture detector is the detector of choice. Before injecting into the column, diclofenac or its metabolites are derivatized into the indolones or the methyl esters.

Calumn

TemDerature

Reference

25mx0.3mm id; coated with barium carbonate and statically coated with Carbowax 40M

24OoC

39,40

2mx3mm id; 3%0V-17 Gas Chrom Q on 80-120 mesh glass beads

3OOOC

38

(methyl silicone) on Gas-Chrom Q

205OC

35

2mx3mm id; 1.5% Silicone OV-17 on Shimalite W AW DMCS, 80-100 mesh.

26OoC

36,37

4 ftx3mm id; 3% JXR

8.2 Thin layer chromatography has been used to analyze diclofenac sodium in suppositories (16 ) and plasma (41).

DICLOFENAC SODIUM

8.3

Perfor-

139

. .

Determination of diclofenac sodium in biological fluids by High Performance Liquid Chromatography were described (42-47 ). The fluids included plasma (42-46 ), urine ( 46 ) and synovial fluid (44). Detection by UV spectrometer was employed with absorbance at 210nm (43 ) , 215nm (44-46 ), 280nm (42 ) and 282nm (46 ). The detection limits are 5-25ng/ml of fluid. Reverse - Phase C,* columns prove to be suitable for diclofenac sodium analysis ( Table I V ). El-Sayed atal employed a rapid sample preparation by precipitating the serum proteins with acetonitrile instead of using phosphoric acid and organic solvent extraction (42 ). Grandjean a d d e s i g n e d an automated robotic extraction and subsequent analysis of diclofenac which could handle large number of samples with little manpower ( 43 ). Analysis from a solid dosage form (tablet) has also been reported (48 ).

forDi-

References

Column Aceton it r ile-w at er ( 50 50, v/v) adjusted to pH 3.3 with glacial acetic acid

42

Spherical C18 (5 Pm)

Isopropanol-acetonitrile-0.02M acetate buffer pH 7 (NaCI 0.02M;5:18:77)

43

Supelcosil LC-18 ( 5 elm)

Methanol-acetonitrile-0.02M sodium acetate buffer (25:20:55)

44,45

Spherisorb RP-C8 column (5 pm)

Methanol-acetonitrile-pH 7 phosphate buffer(30:17:53; v/v)

46

pmbondapak C 18 ( 30 cm x 3.9 cm id)

Methanol 55% in 50mM orthophosphoric acid, pH 4.0

47

Microbondapak CN (30 cm x 3.9 cm id)

Methanol-acetatebuffer (65:35% v/v) pH 3.7

48


140

8.4

SDectroDhotometrlc *Method

Diclofenac sodium may be assayed by simple spectrophotometric method at 600nm inwater ( 49 ). Diclofenac sodium reacted with 3-methyl-2benzothiazolinone hydrazone hydrochloride and cerium ammonium sulfate to form a colored complex which exhibited Am,, at 600nm. H a r l a n d d a l ( 50 ) have also analysed diclofenac sodium spectophotometrically at 275 nm from hydrophilic matrix (polyvinyl alcohol). Other investigations involving analysis by spectrophotometric methods include solubility studies reported by Finiatal( 51) and ongoing work by Vilivallam and Adeyeye ( 52 ). In both cases, the analysis were carried out at 275 nm and 280 nm respectively. 8.5

*Resonance

The proton magnetic resonance (PNMR) method to quantify diclofenac sodium in pure and tablet forms was described ( 3 ). The sharp singlet at 3.62ppm which corresponded to the methylene protonsin diclofenac was chosen for quantitative measurement. Anhydrous sodium acetate was used as internal standard. The methyl protons of sodium acetate gave a sharp singlet at 1.8lppm. The amount of diclofenac could be calculated by comparing the peak ratio of diclofenac to that of the internal standard since the amount of internal was known. The PMR spectrum could also be used to examine the purity of the drug. 8.6 Saneaddescribed a method for determining diclofenac sodium from pharmaceutical preparation by reacting diclofenac sodium with potassium ferricyanide in the presence of sodium hydroxide to form a yellow complex which showed maximum absorbance at 450 nm ( 53 ). Agrawal a a d e s c r i b e d a rapid method for the determination of diclofenac sodium. and reported that the drug solution turned yellow color when reacted with sodium nitrite and hydrochloric acid and exhibited maximum absorbance at 390 nm. Beer’s law was followed in the range of 50-600 pghnl ( 54 ). 8.7

-7

Gas chromatography - Mass spectrometry is the most sensitive method reported in the analysis of diclofenac sodium (1 ). The lowest limit of detection of diclofenac is 0.2 ng/ml of plasma which is 10 times more sensitive than using gas chromatography alone.

141

DICLOFENAC SODIUM

References 1.

H. Kadowaki, M. Shino and J. Vemura, K. Kobayashi, J. Chromatography,U 329 (1 984).

2.

J. Cizmarik and A. Lycka, Pharrnazie,

3.

S. A. Abdel Fattah, S.Z. El-khateeb, S.A. Abdel Razeg and M.S. Twakkol, Spectroscopy Letters, 2-t 5 3 3 ( 1 988)

4.

G. Reck, G. Faust and G. Dietz, Pharmazie, 4;L, 771 (19 8 8 ) .

794 (19 8 8 ) .

5. J. H. Fried, I. T. Harrison, 6. Lewis, J. Riegl, W. Rooks and A. Tomolonis, Scand. J. Rheumatology, Supp. 2 : 77-1 1 ( 1973) 6.

T. Y. S h e n , h " Non Steroidal Anti-inflammatory Drugs", (Ed.) S. Garattini and M. N. G. Dukes, International Symposium Milan ( 1 964)

7.

P. Moser, K. Jakel, P. Krupp, R. Menasse and A. Sallman, J. fur Med. Chern.,1Q, 61 3 ( 1 975)

8.

Y. Tamura, J.4. Venishi, H.D. Choi, J. -I Haruta and H. Ishibashi, Chem. Pharm. Bull. 3.L 1995 ( 1 984).

9.

A. Sallmann and R . Pfister, S. African Patent 6705987, C A : n P i 0697d.

10. T. Nohara, U.K. Patent 20237028, CA:& 11.

Baiocchi, UK Patent 2023578, CA:

15402~.

a 95009

12. A. Sallman U.S. Patent 3558690 13.

L. Horio, Y. Torisawa and S. Ikegami, Chem. Pharm. Bull., 3.L 5562 (1985)

14.

L. Landini, F. Montari and F.M. Pirisi, J. Chem. Soc.. Chern. Commun., 879 ( 1 9 7 4 ) .

15. S. C. Khanna, Ciba-Geigy Patent No. DE 3620631, (1987)


142

16.

L .A. Budukova, T. S. Kondrat'eva, A. P. Echevarria-Uribe, V. D. Arzamastev and V.I. Volchenok, Farmafsiya, 16-20

a

(1 989)

17.

Y.M. El-Sayed, M.E. Abdel-Hameed, M.S. Suleiman and N.M. Najib, J. Pharm. Pharmacol., 4 0 , 727-729 ( 1 9 8 8 )

18.

R, Menass&, P. R. Henwall, J. Kraetz, C. Pericin, Riesterer, L., Sallmann, A., Ziel, R., and Jacques, R., Scand. J. Rheumafology, SUPP. 22: 5-16 (1978)

19.

H.L. White, and A.T. Glassman, Prostaglandins , L 123 ( 1 974)

20.

S. Renauld and F. LeCompte, Thrombosis ef Diafhesis Haemorrhagica (Sfuggarf),_24, 577-586 ( 1 9 7 0 )

21.

F. Jobin, and F.T. Gagnon, Canadian Journal of Physiology and Pharmacology, 479 - 4 8 1 ( 19 7 1 )

22.

W. Reiss, H. Sterlin, P. Degen, J. W. Faigle, A. Ge'rardin , J. Moppert, A. Sallman, K. Schmid, A. Schweizer, M. Sulc, W. Thesbald and J. Wagner, &and. J. Rheumafology, Supp 22: 17-29 (1978)

23.

P. D. Fowler, Clinics in Rheumatic Diseases,A. ( 2 ) , 427-464 ( 1 979)

24.

P. D. Fowler, M. F. Shadforth, P. R. Crook, V. A. Euro, J. Clin. Pharmacol., i& 389 (1983)

25.

J. W. Faigle, I. Boltcher, J. Godbilllon, H. P. Kriemler, E. Schlumpf, W. Schneider, A. Schweizer, H. Stierlin, and T. Winkler, Xenobiofica,J.& ( 1 O ) , 1 191 -1 1 9 7 ( 1 9 8 8 )

26.

F.O. Muller, H.K.L. Hundt, and D.G. Muller, International Journal of Clinical Pharmacology, L5-(9 ) , 3 9 7 - 4 02 ( 1 9 7 7 )

27.

Ciba - Geigy, Baste, Pharmacological Chemisfry Repoft, No. 14 (1977a)

28.

Ciba - Geigy, Basle, Pharmacological Chemistry Report ,No. B 59 (1977b)

143

DICLOFENAC SODIUM

29.

von C. Rosak, and K. Schtiffling, K. Medizinische Welt, 1845 - 1 8 4 6 ( 1 9 7 7 )

30.

K. Chlud, Zeitschrift fur Rheumaforschung ( D), 77-382 (1 976)

31.

F. Michot, K. Ajdacick, and L. Glaus, international Medical Research, 9( 3 ) , 1 53- 1 57 (1 9 7 5 )

32.

J. V. Willis, and M. J. Kendall, Scand. J. Rheumatology, (SUPP), 22, 36-41 (1978)

a

35 (9/1O ) ,

33.

Ciba - Geigy, Pharmacological Chemistry Report, No.37 ( 1 977c)

34.

D. R. Robinson, Amer. J. Med., 84, (supp 2 A ) , 2 (1988)

35.

V.P. Geiger, P.H. Degen and S. Sioufi, J. Chromatography,_LU, 293 ( 1 9 7 5 )

36.

M. Ikeda, M. Kawase, T. Kishie and S. Ohmari, J. Chromatography (Bio App1).273. 486 (1981)

37.

M. Ikeda, M. Kawase, M. Hiramatsu, K. Hirota and S. Ohmori, J. Chromatography, J&L 4 1 ( 1 9 8 0)

38.

A. Schweizer, J.V. Willis, D.B. Jack and M.J. Kendall, J. Chromatography, X& 4 2 1 ( 1 9 8 0 )

39.

W. Schneider and P.H. Degan, J. Chromatography, 11L 263 (1981)

40.

W. Schneider and P.H. Degen, J. C h r o m a r o g r a p h y m 41 2 ( 1 986)

41.

A. Schumacker, H.E. Geissler and E. Mutschler, J. Chromatogr., l & 5 12 ( 1 980).

42.

Y. M. El Sayed, M. E. Abdel-Hameed, M. S. Suleiman, N.M. Najib, ibid, 727 (1988)

43.

D. Grandjean, J.C. Beolor, M.T. Quincon and E. Savel, J. Pharm. Sci., 1 & 247 ( 1989)


144

44.

K.H. Chan and K. H. Vyas, Anal. Lett., 1 & 2502 ( 19 8 5 )

45.

K.H. Chan, K.H. Vyas and K. Wnuck, Anal Lett., U,1649 (1982)

46. J. Grodbillon, S. Gauron and J.P. Metayer J. Chromatography, 151 ( 1981)

.a267-273,

47.

F. Nielsen-Kudsk, Acta Pharmacol et toxicol 1980.

48.

R.T. Sane, R.S. Samant, V.G. Nayak, Drug Dev. lnd. P h a r m . U ( 7 ) , 1307-1314 (1987)

49.

S. Sastry, R.M. Rao and T.N.V. Prasad, Analytical letters, 1Q, 349 ( 1987)

50.

R.S. Harland, A. Gazzaniga, M.E. Sangalli, P. Colombo and N.A. Peppas, Pharm Res. 8 ) ( 19 8 8 )

51. A. Fini, V. Zecchi and A Tartarini, Pharm. Acra. Helv. M ( 2 ) , 58 ( 1985) 52. V. Vilivallam and C. M. Adeyeye, unpublished data 53.

R.T. Sane, R.S. Samant and V.G. Nayak, Indian Drugs, 14, 161 (1986).

54. Y.K. Agrawal, V.P. Upadhaya and S.K. Menon, Indian J. Pharma. Sci., 58 (1988) .

a

ANALYTICAL PROFILE OF DIETHYLSTILBESTROL

Abdullah A. Al-Badr** M e 1 G. Mekkawi*

**Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University

*Riyadh Health Institute, Ministry of Health, Riyadh.


145

Copyright B 1990 by Academic Press,Inc. All rights of reproduction in any form reserved

ABDULLAH A. AL-BADR AND ABDEL G. MEKKAWI

146

CONTENTS 1. Description.

Nomenclature Formulae Molecular Weight Elemental Composition 1.5 Appearance, Color and Odor

1.1 1.2 1.3 1.4

2. Physical Properties. 2 . 1 Solubility 2 . 2 Melting Range 2 . 3 Spectral Properties 2.3.1 2.3.2 2.3.3 2.3.4

Ultraviolet Infrared Nuclear Magnetic Resonance Mass

2 . 4 Crystalography and X-Ray Crystalography 2 . 5 Thermal Analysis 2 . 6 X-Ray Powder Diffraction 3. Synthesis. 4. Physiology, Pharmacology and Uses.

5. Pharmacokinetics.

6. Methods of Analysis. 6.1 6.2 6.3 6.4 6.5 6.6

Identification Titrimetric Methods Spectrophotometric Methods Polarographic Methods Chromatographic Methods Radioirnmunoassay Methods

7. Metabolism

Acknowledgement References.

147

DIETHYLSTILBESTROL

1. DESCRIPTION 1.1

1.1.1

Nomenclature Chemical Name 3,4-Di(p-hydroxyphenyl)hex-3-ene. 3,4-Bis(p-hydroxyphenyl)-3-hexene. 4,4(1,2-Diethyl-1,2-ethenediyl)bis(E)phenol. -4,4*-Dihydroxy-GP-diethylstilbene. a,&-Diethylstilbenediol.

a,&-Diethyl-(E)-4,4’-Stilbenediol. trans-a,&-diethyl-4,4’-Stilbenediol

1.1.2

(1-4).

Generic Names Diethylstilbestrol; Diethylstilboestrol; DES, Stilbestrol; Stilboestrol; Stilbol (2,3,5).

1.1.3

Properietary Names Antigestil; Bio-des; Biofon; Cyren A; Distilbene; Domestrol; Estrobene; Estrosyn; F o r n a t o l ; Grafestrol; Hi-Bestrol; Microest; Neo-Oestranol 1, Oes trogenine; O e s t r o m e n i n; O e s t r o m e n s y 1 ; Oe st romon; Palest rol ; Percutacrine Oestrogenique Iscovesco; Serral; Sexocretin; Sibol; S t ilbetin; Stilboef ra; Stilboestroform; Stilkap; Synestrin (Tablets); Synthoestrin (1-5).

1.2 Formulae 1.2 1 Empirical 18*20°2

1.22 Structural


148

1.23 CAS registry No. [ 56-53-1

1.

1.3 Molecular Weight 268.4 1.4 Elemental Composition C 80.56%, H 7.51%, 0 11.92%. 1.5 Appearance, Color and Odor

White or almost white, crystalline powder and is odorless (2,4). 2. PHYSICAL PROPERTIES 2.1 Solubility Very slightly soluble in water, soluble solutions of alkali hydroxides, soluble in ether, in 5 parts of 95% v/v alcohol and in arachis oil, slightly soluble in chloroform

in aqueous 3 parts of 40 parts of (2,4).

2.2 Melting range 169-175'C

(1).

2.3 Spectral Properties 2.3.1

Ultraviolet Spectrum

The ultraviolet spectrum of diethylstilbestrol in 0.1N sodium hydroxide, maximum at 259 nm ( E l % , 1 cm 764). (2). The ultraviolet spectrum of diethylselbestrol in ethanol is obtained using Cary, 219 spectrophotometer and is shown in Figure [l]. The spectrum shows a major band at 240 nm and a minor band at 280 nm. 2.3.2

Infrared Spectrum

The infrared spectrum of diethylstelbestrol as KBr disc is presented in Figure [2] and is recorded in PerkinElmer spectrophotometer model 580 B. The structural

DIETHYLSTILBESTROL

149

Wavelength ( n m )

300

400

Figure I : Ultrwiokl spectrum of Diethylstilbcstrd in ethanol

MICRONS I

4olm 3000 2500 2000 la00 1600 1400 1000 800 Wavenumber Figure 2 : Infrared spectrum of Diethylstilbestrol, KBr disc.

600

400 200


150

assignments have been correlated with band frequencies and are given in the following table :Frequency (cm")

Assignment

1592,1612 2990 3420 1340 830

C=C stretch (aromatic) C-H stretch OH stretch C-H bending C-H bending (aromatic)

Clarke (2) reported the following principal peaks as KBr disc: 1198, 1515 and 1165 cm-'. 2.3.3 Nuclear Magnetic Resonance Spectra 2.3.3.1

Proton Magnetic Resonance Spectrum (PMR)

The PMR spectrum of diethylstilbestrol was recorded on varian T-60 A spectrometer with DMSOd6 as a solvent and TMS (tetramethylsilane) as internal reference. The spectrum is shown in Figure [31 and the signal are assigned as follows:Proton

6.6 - 7.1 0.65 2.05 9.16

Phenyl protons CH3 CH2 OH 2.3.3.2

Mu1t iplicity

Chemical shift (ppm)

Multiplet Triplet Quartet

Carbon-13 NMR Spectra

The Carbon-13 NMR noise-decoupled and of fresonance spectra are presented in Figures [ 4 ] and 151 respectively. The samples were dissolved in DMSO-d6 and the spectra were obtained on Jeol-XL100 NMR spectrometer using tetramethylailane (TMS) a s i n t e r n a l r e f e r e n c e standard. Spectral assignments are listed below: a'

9'

CH2CH3 140

-' H

!(

3

CH 8 2

3'

2'

ioo

200

300

0

c , . ' . . * * 1 * - .

.

~

-

.

"

~

.

"

'

~

-

.

.

.

~

.

.

.

.

~

.

.

.

.

~

.

.

~

.

8.0 7.0 6.0 s.oppM( 6 40 3.0 2.0 LO 0 Figure 3: Proton nuclear magnetic resonance spectrum of Diethylstilbestrol in DMSO-dg using TMS as reference standard.

1

152


figure 4 : Proton -decoupled carbon-I3 NMR spectrum

Of

DiethylsteLkstrol i n

DMSO-d6 using TMS as reference standard.

-

Figure 5: Off-Resonance carbon I3 NMR spectrum of Diethylstelbestrol in D M s 0 - d ~using TMS as reference standard.

DIETHYLSTILBESTROL

Carbon No.

153

Chemical Shift (ppm) relative to TMS

1 and 1’ 2,2‘ and 6,6’ 3,3‘ and 5,5’ 4 and 4’ 7 and 7’ 8 and 8‘ 9 and 9’ 2.3.4

155.58 114.78 129.22 137.85 132.45 28.00 13.27

Multiplicity Singlet doublet doublet singlet singlet triplet quartet

Mass Spectrum

The electron impact (EI) mass spectrum at 70 eV recorded on Varian Mat 311 mass spectrometer and the methane-derived chemical ionization (CI) mass spectrum obtained with Finnigan 4000 mass spectrometer are shown in Figures [ 6 ] and [ 7 ] respectively. Scheme ( 1 ) shows the proposed fragmentation pathway. Low resolution mass spectra for diethylstilbestrol, dienestrol, hexestrol, the acetates of them, dimethyl, the bis-(trimethylsilyl) ethers, and some deuterated derivatives of these were studied by Engel -et a1 ( 6 ) . 2.4 X-Ray Chrystallography

Simley and Rossmann ( 7 ) have determined the crystal structure of diethylstilbestrol because of the interest in its biological activity. Crystal of the drug are orthorhombic with a = 19.18, b = 5.32 c = 15.01 A . , 2 = 4 , calculated d = 1.164, experimental d = 1 . 1 6 2 , and space group Pcab. The planes of the two benzene rings were paralleled but not coplanar. This loss of coplanarity resulted from steric effect between the methylene carbon of the ethyl group and the orthohydrogen atoms. The bond length A and angles ( 0 ) are listed below (Table 1) and Figure I81 gives a respective view of the molecule. Busetta and Hospital ( 8 ) have studied the crystalline structure of diethylstilbestrol. The drug was crystallized by sublimation in the form of orthorhombic needles, space group Pbca with a = 18.992 + 0.005, b = 14.931 + 0.005 and c = 5.296 + 0.005 A; Z =-4. The unit

ABDULLAH A. AL-BADR AND ABDEL G . MEKKAWI

154

loo.(

2

i680.

ME50 100 I50 200 250 300 Figure 6 : Electron impact ( E l lmass spectrum of Diethylstilbestrol

1000-

5 0.0-

'4472.

m/e268

m / e 253

m / e 1-19

czH5 -HO-Q-c=C-Q-OH Scheme 1:

m/e268

m/e91

C2H5

m / e 239

l+

m/e210 Proposed fragmentation pathway of diethylstilbestrol.

-r

A

ro r tm V

6

4

E

I

-

-

f I' "II ' s

$0 I V

Ot I

0

N

I

to

G

I

I '

\

aJ E

0 c

fi

E

\

aJ

6

8 r q 4-

156

Scheme 1 :

Proposed fragmentation (continued).

pathway of

diethylstilbestrol

158

ABDULLAH A. AL-BADR AND ABDEL G . MEKKAW

Figun8:Molecular stereochemistry of

-

aa/diethylstilbene 44’-d io I

DIETHYLSTILBESTROL

159

of symmetry i s h a l f a molecule, and t h e molecules a r e bonded t o e a c h o t h e r w i t h hydrogen bonds 3A long and with a d i h e d r a l a n g l e of 88’. Table (1) Bondlength A

and Bond a n g l e s

C( l.)-C(l)-C(8) C( l)-C(8)-C(9) C( 1)-C( 1 )-C(2) C(2)-C( 1)-C(8) C(3)-C(2)-C(7) C(2)-C(3)-C(4) C(3)-C(4)-C(5) C(4)-C(5)-C(6) C( 5)-C( 6)-C( 7) C(2)-C(7)-C(6) C( 4)-C( 5)-0 C(6)-C(5)-0

(0)

124.07 109.32 122.22 113.78 116.05 125.15 116.27 122.65 119.15 121.65 119.57 117.80

The c r y s t a l s t r u c t u r e of d i e t h y l s t i l b e s t r o l was a l s o s t u d i e d i n r e s p e c t t o e s t r o g e n i c a c t i v i t y by Weeks et a 1 (9). The d r u g ( s i n g l e c r y s t a l s ) were grown by s l o w l y c o o l i n g a s o l u t i o n of t h e d r u g i n a 0.01 M s o l u t i o n of p - c h l o r o p h e n o l i n i s o - o c t a n e . The m o l a r r a t i o of p - c h l o r o p h e n o l of t h e drug i n t h i s s o l u t i o n was 2:l. The s y s t e m a t i c absences (OK1 f o r K odd, h01 f o r 1 odd, and hKO f o r h o d d ) i n t h e d i f f r a c t i o n p a t t e r n , were c o n s i s t a n t w i t h t h e o r t h o r h o m b i c s p a c e group Pbca and t h e c r y s t a l d a t a a r e :

2 0.004, b = 14.929 + 0.001 5.291 + 0.001 A ( a t 2OoC, Cu Kal = 1.5045 A) V = 1497.29 A3, Dm = 1.14 g.cm Dc = 1.19 g . ~ m ‘ ~ , u = 6.1 cm-I (by f l o t a t i o n ) , Z = Space group Pbca, D1”no.61. a = 18.954

c

=

The a u t h o r s have p r e s e n t e d a t a b l e showing t h e agreement b e t w e e n t h e o b s e r v e d and c a l c u l a t e d s t r u c t u r e f a c t o r amplitudes. Table 2 shows a l i s t of t h e r e f i n e d atomic c o o r d i n a t e s and t h e thermal parameters. The i n t e r a t o m i c d i s t a n c e s and valency a n g l e s i n v o l v i n g n o n h y d r o g e n a t o m s a r e shown i n F i g u r e [9] (Standard d e v i a t i o n a r e i n t h e range of 0.006-0.01 A and 0.2-0.7 An u n u s u a l l y s h o r t a p p a r e n t d i s t a n c e of respectively). 1.498 A between C(8) and C(9) r e s u l t from t h e l a r g e thermal motion of C(9). C-H d i s t a n c e l i e s i n t h e range

exp [ 2

0.15324(27) 0.21313(25) 0.21507(22) 0.153%(25) 0.09949(23) 0.09571(23)

0.03131(24) 0.04616(27) 0.07880(32) 0.27396(16)

(U h2a* + 2UI2hka*b* +

0.03507(33) 0.08731(33) 0.14632(28) 0.15144(31)

0.09820(31) 0-04043(28) 0.01726(25) 0.11730(29) 0.14524(35) 0.20083(20)

-0.0921 4.0548 -0.1462 4.3118 -0.2722 -0-0669 -0.0233 -0.0418 -0.2873 4.17M

9) 9) 8) 9) 9) 8) 8) (10) (12) ( 6) ( ( ( ( ( ( (

...11

0.0680(30) 0.0576(26) O.W5(22) 0.0563(27) 0.0479(24) 0.0555(24) 0.0601(23) 0.0633(28) 0.0818(36) 0.0508(17)

0.0474(24) 0.0505(24) 0.0378(21) 0.0523(27) 0.0518(25) 0.0357(20) 0.0291(21) 0.0302(21) 0.0482(28) 0.0456(16)

Table 2 ( b ) : Atomic coordinates of t h e hydrogen atoms. 0.1543 0.2524 0.1707 0.0618 0.0849 -0.01 18 0.0630 0.1342 0.0804 0.2729

-0.0025 -0.0827 -0.1876 -0.1044 -0.1348 -0.1470 -0.1087 -0.1313 -0.2026 -0.2250

-0.2554 -0.1638 -0.4613 -0.3899 -0.0820 -0.0545 -0.4219 -0.2757 -0.3422 -0.3303

0.0533(26) 0.0548(26) 0.0587(26) 0.0556(27) 0.0581(26) 0.047’l(23) 0.0536(24) 0.0811(34) 0.0876(41) 0.0700(23)

-0).O020(22) -0.0058(22)

-0.0081(20)

-0.a)69(2l) -0.0087(19) -O.a)82(22) d0093(21) -0.0071(22) -0.0011(21) -0.U32l(l8) -0.0110(19) -0.0040(17) -0.OllX21) 4-0042(20) -0.0140(25) -0&092(26) -0JB88(30) -0.0126(14) -0.0014(16)

-0.0056(20)

-0.0056(2l) -0.0001(17)

-0.0033(18) -0.0106(20) -0.0102(21) -0.002l( 17) 4.0004(17) 4.00l2(21) -0.0213(27) -0).M)56(16)

Ho OH

Figure9:lnteratomic distances and valency angles. Corrected for thermal motion ( 9 ) .

162


of 0.91 t o 1.19 A, with average v a l u e of 1.00 A. 0 -H d i s t a n c e i s 0.92 A.

The

A c l o s e i n t e r m o l e c u l a r c o n t a c t of 3.03 A occurs between oxygen atoms. The a n g l e OH---0 i s 171°, and t h e H----0 d i s t a n c e i s 2.11 A. The system of h y d r o g e n bonds a n d t h e packing of t h e molecules a r e i l l u s t r a t e d i n f i g u r e [ l o ] which i s a p r o j e c t i o n of one u n i t c e l l down t h e c axis.

Neither t h e benzene r i n g s nor t h e a l k y l groups l i e i n t h e plane of t h e c e n t r a l e t h y l e n i c l i n k a g e . Since t h e atoms comprising t h e benzene r i n g l i e n e a r l y i n a p l a n e a s do t h o s e a t t a c h e d t o t h e c e n t r a l d o u b l e bond, t h e g e o m e t r y of t h e m o l e c u l e i s f i x e d when t h e t o r t i o n a l a n g l e s a b o u t t h e C(6)-C(7) and C(7)-C(8) bonds a r e d e f i n e d . T h e s e a n g l e s a r e l i s t e d i n T a b l e ( 3 ) . The a n g l e formed by t h e l e a s t - s q u a r e p l a n e t h r o u g h t h e e t h y l e n i c l i n k a g e and t h e p l a n e t h r o u g h t h e benzene r i n g i s 62.8'. Since t h e molecule l i e on c r y s t a l l o g r a phic c e n t r e of symmetry, t h e a n g l e s of r o t a t i o n of t h e two r i n g s a r e i d e n t i c a l . The t h r e e dimensional configur a t i o n of t h e molecule i s i l l u s t r a t e d i n F i g u r e [ l l ] . Rotation of t h e r i n g s o u t of t h e c e n t r a l plane g i v e t h e m o l e c u l e a t h i c k n e s s of a b o u t 4.5 A , which i s comparable t o t h e t h i c k n e s s of a s t e r o i d a l e s t r o g e n a t C(18). The r e s u l t s of t h i s X-ray i n v e s t i g a t i o n c o n f i r med t h a t t h e s y n t h e t i c e s t r o g e n , d i e t h y l s t i l b e s t r o l h a s a non p l a n a r conformation. A s shown by t h e d i s t a n c e between t h e p h e n o l i c oxygen atoms, it i s a molecule s l i g h t l y l o n g e r t h a n t h e n e u t r a l e s t r o g e n s , b u t t h e r o t a t i o n of t h e b e n z e n e r i n g s o u t of t h e p l a n e of t h e c e n t r a l d o u b l e bond r e s u l t s i n a molecular dimention similar t o the t h i c k n e s s of a s t e r o i d a l e s t r o g e n .

a

0

U

2

U

7 2 :

7

c

0

U

.s

.-c .u

8 m

.-C

a

-I V

P

Figure1l:Three dimensional conformation of diethylstilbestrol ( 9 1.

DIETHYLSTILBESTROL

165

Table 3 : T o r s i o n a l a n g l e s f o r one asymmetric u n i t of the structure. Angle

C(l)-C(6)-C(7)-C(7’) C(l)-C(6)-C(7)-C(8) C(5)-C(6)-C(7)-C(7’) C(5)-C(6)-C(7)-C(8) C(6)-C(7)-C(8)-C(9) C(9)-C(8)-C( 7)-C( 7‘)

-118.6’ 62.1 63.4 -115.9 56.0 -123.3

The c e n t e r of symmetry c r e a t e s a n g l e s i n t h e o t h e r h a l f of t h e molecule which have t h e o p p o s i t e s i g n .

2.5 Thermal A n a l y s i s The t h e r m a l a n a l y s i s o f d i e t h y l s t i l b e s t r o l was done between 100°C and 250°C a t a h e a t i n g r a t e of 10°/minute ( F i g u r e [12]). P u r i t y of sample was found t o be 99.86%. Heat of f u s i o n of t h e s a m p l e was found t o be 31.9 Km/mole (7.62 Kcal/mole).

2.6 X-Ray Powder D i f f r a c t i o n The X-ray d i f f r a c t i o n p a t t e r n s of d i e t h y l s t i l b e s t r o l was d e t e r m i n e d u s i n g P h i l i p s f u l l a u t o m a t e d X-Ray d i f f r a c t i o n Spectrogoniometer equipped with PW 1730/10 g e n e r a t o r . R a d i a t i o n was p r o v i d e d by a c o p p e r t a r g e t (Cu anode 2000 w, 8 = 1.5480 A) h i g h i n t e n s i t y x-ray The monochromator t u b e o p e r a t e d a t 40 Kv and 35 mA. was a c u r v e d s i n g l e c r y s t a l o n e (PW 1752/00). Divergance s l i t and t h e r e c e i v i n g s l i t were 1 and 0.1’ respectively. The scanning speed of t h e goniometer (PW 1050/81) used was 0.02-28 p e r second. The i n s t r u m e n t i s combined w i t h P h i l i p s P M 8210 p r i n t i n g r e c o r d e r w i t h b o t h a n a l o g u e r e c o r d e r and d i g i t a l p r i n t e r . The goniometer was a l i g n e d u s i n g s i l i c o n sample b e f o r e use. The x-ray p a t t e r n of D i e t h y l s t i l b e s t r o l i s p r e s e n t e d i n F i g u r e [13]. The i n t e r p l a n n e r d i s t a n c e s d(A) and r e l a t i v e intensity 1/10 a r e shown i n t h e f o l l o w i n g table:-

166


171.6

0-

L--.

'...

-

-1-

-171.4 3

-171. 2

'....DO

.'?

0

.c0

,. 0.q

E -2-

-171.0 P.*

g-,

Purity : 99.86 yole '1. Melting pt : 171.5: Depression : 0.07C * 31.9kJlmole LL 4- Delta H Correction : O.OO*/.

-8 -

-6-7-

Y

"m

-170.8

"U..

-170.6 b...,

-

2IV -5 -

b..., 'b

-169.8

I5

Ip

5

7. 6.

5-

4. 32I07065

55

. -170.2 -170.0

Total Area I Partial Area

45

35

25

15

5

28 Figure 13: The X-Ray ditfraction pattern of diet hy Ist i I best rol

-5L

3

n

-170.4 E

b....

Mol.Weight : 268.3g1Mole Cellconst : 1.282 Onset slope : 7.90mw1d

0

-

*V

$

167

DIETHYLSTILBESTROL

X-Ray Diffraction Patterns of Diethylstilbestrol d(A)

1/10

9.54 8.06 7.51 5.90 4.85 4.54 4.43 4.33 4.22 4.01 3.94 3.74 3.57 3.44 3.39 3.17 3.10 3.05 3.03 2.91 2.85 2.75 2.56 2.52

16.40 14.03 20.14 48.03 100.00 51.49 65.06 18.11 27.88 17.98 27.23 12.93 35.93 39.11 22.00 11.35 10.49 7.97 8.02 20.58 5.27 3.35 8.31 7.46

d(A)

1/10 9.47 4.42 6.59 6.22 5.44 3.28 3.84 6.29 9.91 3.08 3.54 3.04 3.14 2.93 3.14 3.38 3.49 3.80 2.48 2.42 2.66 1.40 1.37

2.50 2.41 2.38 2.32 2.30 2.24 2.20 2.17 2.14 2.10 2.03 2.00 1.96 1.93 1.89 1.88 1.83 1.75 1.68 1.63 1.56 1.39 1.38

3. SYNTHESIS

Several methods have been reported f o r the synthesis of diethylstelbestro1:1)

et a1 ( 1 0 T h e d r u g w a s f i r s t prepare1 by DO( ds a,b) according to the following scheme:OH


168

72H5 , , C O G

H3C0

H3C0

c-

a :.;!.f

co

C2H5 Mg Br

--@

t

OCH3

PBr

dI

OCH3

4

-H20 -

C2H5

-@C2H5 A ~= -@ ocu3 * - ethanolic

KOH

1

2)

C H 2 5 Kharasch and Kleiman ( 1 1 ) p r e p a r e d t h e d r u g by t r e a t i n g a n e t h o l e hypobromide w i t h sodamide i n l i q u i d ammonia t o form a c a r b a n i o n which r e a c t w i t h u n r e a c t i n g s t a r t i n g m a t e r i a l and t h e n t h e e l i m i n a t i o n of h y d r o g e n b r o m i d e f o r m s a n i n t e r m e d i a t e w h i c h on d e m e t h y l a t i o n g i v e diethylstilbestrol.

DIETHYLSTILBESTROL

hH

169

O e Y = h * O H

C2H5

C2H5 3)

Kuwada -e t a1 ( 1 2 ) have prepared the drug according t o the f o l l o w i n g scheme :-

CN I C2H5MgBr C2H5-CH-OH

OH I H3COC6H4MgBr C2H5-CO-CH-C2H5 c

72H5

c -CH--

H3C0G-,

H3C0

I

I

OH

‘2*’5

@Z12H Y C O - C H

2 5

30% H,SO4

OH

b

H3CO-C 6H 4-MgBr

b

OH

H3C0

=( @ ’; C2H5

@-OC3H

C&-?C=

I

C2H5

C2H5

OCH3

HC 1

.----+

H

OCH3-

R MgBr

+

170


4)

Alder et a1 (13) have reported the synthesis of diethylstilbestrol according to the following scheme:-

OH

C2H5 H C 1 gas

._____)

E-co

OH

*OAc

Na/AmOH 140°

-H,O L

C2H5 H HO

-@[2H5 C2H5

H C 1 gas -H20

bI -@OH

>

OH f2H5

HO-@

5)

f=c C2H5 Shishido and Nozaki (14) reported the synthesis of diethylstilbestrol through the pinacol-pinacolone compounds according to the following scheme:

CH

Mg B r

f

DIETHYLSTILBESTROL

171

6)

Yoshida and Akagi (15) have reported the synthesis of the drug by treating p-CH30C6H4CHEtC(OH)EtC6H40CH3-P with POC13 in boiling toluene.

7)

A method for the synthesis of diethylstilbestrol have been reported by Slager (16). It involves the

conversion of 3,4-bis-(p-hydroxyphenyl)- 3,4hexandiol to 3,3-bis(p-hydroxyphenyl)-4-hexanone, treatment with Et4NBr and Et4NOH and electrical reduction to give the drug. OH

OH &OH

-H20*0

F2HS C-COC2H5 I

C2HS

4. PHYSIOLOGY, PHARMACOLOGY AND USES Diethylstilbestrol is a synthetic nonsteroidal estrogenic compound that exhibits the characteristic physiological actions of the hormonal class estrogens, these hormones are largely responsible for the changes that take place at puberty in girls and they go a long way for the tangible and intangible attributes of femininity (17). They affect the body, building and function; the biological role, the physiology, the thinking and psychology of the female. Diethylstilbesterol is indicated clinically for purposes where estrogenic effects are needed. On molecular basis, 1.6 mg. of diethylstilbestrol diphosphate is approximately equivalent to 1 mg. of diethylstilbestrol. The drug is indicated for the following clinical purposes: 1) Cancer treatment

Diethylstilbestrol exerts the usual inhibitory effects of estrogens on androgen dependent carcinomas and also exerts a direct cytotoxic action due to release of free s t i 1 b e s t r ol w i thin the neoplasm ( 1 8 , 1 9 , 2 0) Suc h cancers include prostatic cancer where the level of the

.


172

hormone is prostatic tissues was 100 times greater than that in the fat and muscle (20,211. The hormone also suppresses pituitary Lutenizing hormones and hence suppression of androgenic stimuli (20-23). 2) Suppression of Lactation

Diethylstilbestrol is used to suppresses lactation particularly post-partum lactatibn and galactorrhea (24-26) 3) Polycythemia Vera Treatment

Wirth (27) used diethylstilbesterol to improve cases of polycythemia Vera. 4) Symptomatic Relief of Menopause

Diethylstilbesterol has been used with success in symptomatic relief of menopause. It is reported that diethylstilbesterol supplementation may delay the onset of oesteo porisis in post-menopausal women (28,29).

5) Post-hysterectomy Use Diethylstilbesterol like other estrogens is a definite indication for post hysterectomy menopause to prevent vaginal atrophy and hot flashes (29-31). 6) Contraception Diethylstilbestrol use in oral contraceptives is no longer popular but its indication in post coital contraception is still widely used (FDA drug bulletin, 1973). 7) Other Indications

Other indications where diethylstilbestrol is used include: Postpartum breast engorgement, Duchennes muscular dystrophy, after sexual assault, sickle cell disease, dysfunctional uterine bleeding, failure of ovarian development and acne (17,32,33).

173

DIETHYLSTILBESTROL

8 ) Adverse E f f e c t s A d v e r s e s i d e e f f e c t may i n c l u d e h e a d a c h e , n a u s e a , v o m i t t i n g and m i l d d i a r r h o e a . R e c e n t l y i t h a s b e e n p o s t u l a t e d t h a t long d u r a t i o n t h e r a p y may p r e c i p i t a t e some c o m p l i c a t i o n s i n some p a t i e n t s , s u c h a s v o i c e c h a n g e , m a l i g n a n t changes, p e r e p h e r a l venous thrombos i s , pulmonary e m b o l i s m , h y p e r t e n s i o n and s t r o k e ( 1 7 , 3 0 , 32-35). The d r u g i s t e r a t o g e n i c , may induce malformation and malfunction i n o f f s p r i n g s of pregnant women who use it. 5. PHARMACOKINETICS D i e t h y l s t i l b e s t r o l i s r e a d i l y absorbed from t h e g a s t r o i n t e s t i n a l t r a c t . The d r u g i s d i s t r i b u t e d t h r o u g h o u t body t i s s u e s . I t i s bound i n 50-80% t o p r o t e i n s ( 3 4 , 3 5 ) . Borozdina e t . a l . (36) detected r e s i d u a l d i e t h y l s t i l b e s t r o l i n meat o f a n i m a l s f e d t h e drug. The compound was d e t e c t e d i n t h e f a t , m e a t , l i v e r and kidneys. A f t e r a s i n g l e subcutaneous i n j e c t i o n t h e drug was completely e l i m i n a t e d a f t e r 5 d a y s , i n r o o s t e r s ( 3 6 ) , t h e drug i s slowly i n a c t i v a t e d i n t h e l i v e r and e x c r e t e d i n u r i n e and f a e c e s , p r i n c i p a l l y a s g l u c u r o n i d e (17,35-37) and a s t h e s u l p h a t e (37-39). I n p r o s t a t i c cancer p a t i e n t s t h e l e v e l of t h e hormone was 100 times h i g h e r i n p r o s t a t i c t i s s u e s t h a n i n f a t and muscle ( 2 0 , 2 1 ) . It i s n a t u r a l t o a n t i c i p a t e h i g h e r c o n c e n t r a t i o n s of t h e hormone i n i t s n a t u r a l t a r g e t t i s s u e s t h a n t h e r e s t of body t i s s u e s (17,32,33,39). 6. METHODS OF ANALYSIS 6.1 I d e n t i f i c a t i o n T e s t s The f o l l o w i n g t e s t s a r e d e s c r i b e d i n B.P.

1980 (4):-

1)

The l i g h t a b s o r p t i o n , i n t h e range 230 t o 350 nm, of a 2-cm l a y e r of a 0.001 p e r c e n t w/v s o l u t i o n i n a b s o l u t e e n t h a n o l e x h i b i t s a maximum o n l y a t 241 nm; absorbance a t 241 nm, about 1.2.

2)

The l i g h t a b s o r p t i o n , i n t h e range 230 t o 450 nm, of t h e i r r a d i a t e d s o l u t i o n prepared a s d i r e c t e d i n t h e a s s a y , e x h i b i t s two maxima, a t 292 nm and 418 nm.

174


3)

Dissolve 0.5 mg in 0.2 ml of glacial acetic acid, add 1 ml of orthophosphoric acid and heat on a water-bath for three minutes; a deep yellow color is produced which almost disappears on dilution with 3 ml of glacial acetic acid.

The following identification tests are described in USP

xx

(1) :

1)

Prepare an alcoholic solution containing 10 ug of USP diethylstilbestrol RS and diethylstilbestrol respectively in each ml. Determine the absorbance of each solution in the range 230 to 350 nm, using alcohol as the blank. The spectrum of diethylstilbestrol exhibits a maximum and an additional inflection at the same wavelength as that of the solution of USP diethylstilbestrol RS, concomitantly measured, and the absorpitivity of diethylstilbestrol at the wavelength of maximum absorbance does not differ from that of the Reference Standard by more than 3.0%.

2)

Prepare the standard preparation as follows: "Dissolve in alcohol a suitable quantity of USP diethylstilbestrol RS, accurately weighed and prepare, by stepwise dilution with alcohol, a solution containing about 20 ug per ml of this solution with an equal volume of dibasic potassium phosphate solution (1 in 55). Transfer 4 ml of this standard preparation to a stoppered, 1-cm quartz cell, place about 5 cm from a low-pressure, short wave mercury lamp, rated at from 2 to 20 watts, and irradiate €or about 5 minutes. Measure the absorption spectrum, in the range of 250 to 4 5 0 nm of this yellow solution exhibits inflections only at the same wavelengths as that of the solution obtained after irradiation of the standard preparation.

6.2 Titrimetric Methods 6.21 Volumetric Determination

Stilbestrol dipropionate was determined volumetrically by Gyenes ( 4 0 ) using the bromination method. 72-82 mg in acetic acid (in 20 ml acetic

DIETHYLSTILBESTROL

175

a c i d ) were t r e a t e d w i t h 0.1 N KBr03 (10 m l ) , H2S04 ( l : l , 0.5 ml) and K B r (300 mg i n 1 m l of H 0 ) i n a s t o p p e r e d f l a s k and l e f t i n t h e dark a t 35' + 3' f o r 80 t o 83 min. K I ( 5 0 0 mg i n 20 m l H20)-was added f o l l o w e d by s t a r c h s o l u t i o n and t i t r a t e d a g a i n s t 0.1 N t h i o s u l p h a t e s o l u t i o n . One molecule o f t h e d r u g consumes 4 e q u i v a l e n t s of bromine. However, f o r s t i l b e s t r o l t h e r e a c t i o n t i m e b e f o r e t i t r a t i o n was 25 minutes. The l i m i t of e r r o r f o r s t i l b e s t r o l was 2 0.5%. Elsayed and Obiakara (41) a s s a y e d s t i l b e s t r o l i n t a b l e t s and powders by s l i g h t l y modifying t h i s method and d i s c u s s e d t h e r e a c t i o n k i n e t i c s i n r e s p e c t t o time of a d d i t i o n and bleaching of t h e r e a g e n t . They c o n c l u d e d t h a t t h e method i s s u i t a b l e f o r r o u t i n e work i f o t h e r p h e n o l i c compounds a r e absent. 6.3 Spectropho tome t r y 6.31 C o l o r i m e t r i c Methods B r i t i s h Pharmacopeia 1980(4) d e s c r i b e d t h e followi n g procedure: D i s s o l v e 20 mg i n s u f f i c i e n t a b s o l u t e e t h a n o l t o produce 100 m l and d i l u t e 10 m l t o 100 m l with t h e same s o l v e n t . To 25 m l of t h e r e s u l t i n g s o l u t i o n add 25 m l of a s o l u t i o n prepared by d i s s o l v i n g 1 g of a n h y d r o u s d i p o t a s s i u m hydrogen orthophosphate i n 55 m l of w a t e r , t r a n s f e r a p o r t i o n of t h e m i x t u r e t o a 1-cm c l o s e d q u a r t z c e l l , p l a c e t h e c e l l 10 cm from a 15-watts, shortwave, u l t r a v i o l e t l a m p , and i r r a d i a t e f o r t e n minutes. Measure t h e a b s o r b a n c e of t h e i r r a d i a t e d s o l u t i o n a t t h e maximum a t about 418 nm, and c a l c u l a t e t h e c o n t e n t of C8H2002 f r o m t h e a b s o r b a n c e o b t a i n e d by r e p e a t i n g t h e o p e r a t i o n using d i e t h y l s t i l b e s t r o l EPCRS i n s t e a d of t h e s u b s t a n c e being examined. United S t a t e Pharmacopia XX( 1 ) d e s c r i b e d t h e f o l l o w i n g procedure: Standard p r e p a r a t i o n : Dissolve i n alcohol a s u i t a b l e q u a n t i t y of USP d i e t h y l s t i l b e s t r o l R S , a c c u r a t e l y w e i g h e d , and p r e p a r e , by s t e p w i s e

176


d i l u t i o n w i t h a l c o h o l , a s o l u t i o n c o n t a i n i n g about 20 ug p e r m l . Mix 25 m l of t h i s s o l u t i o n w i t h a n e q u a l volume of d i b a s i c p o t a s s i u m p h o s p h a t e s o l u t i o n ( 1 i n 55). Assay p r e p a r a t i o n : Proceed with a s u i t a b l e q u a n t i t y , a c c u r a t e l y w e i g h e d , of d i e t h y l s t i l b e s t r o l a s d i r e c t e d under Standard p r e p a r a t i o n . Procedure: (Caution - P r o t e c t t h e e y e s from d i r e c t r a y s oE u l t r a v i o l e t l i g h t t h r o u g h o u t t h i s procedure). T r a n s f e r 4 m l of t h e S t a n d a r d p r e p a r a t i o n t o a s t o p p e r e d , 1 cm q u a r t z c e l l , p l a c e a b o u t 5 cm from a low-pressure, shortwave mercury lamp, r a t e d a t f r o m 2 t o 20 w a t t s , and i r r a d i a t e f o r about 5 minutes. P l a c e t h e c e l l i n t h e sample compartment of a s u i t a b l e spectrophotom e t e r , and m e a s u r e t h e a b s o r b a n c e a t t h e wavelength of maximum absorbance a t about 418 nm, u s i n g water a s t h e blank. Continue i r r a d i a t i o n f o r s u c c e s s i v e 1 t o 3-minute i n t e r v a l s , m e a s u r i n g a t 418 nm u n t i l t h e maximum absorbance (about 0.7) has been o b t a i n e d . I f n e c e s s a r y , a d j u s t t h e g e o m e t r y of t h e i r r a d i a t i o n a p p a r a t u s so a s t o o b t a i n maximum, r e p r o d u c i b l e absorbance a t 418 nm. S i m i l a r l y , i r r a d i a t e a 4-ml p o r t i o n of t h e a s s a y p r e p a r a t i o n , r e c o r d i n g t h e a b s o r b a n c e a t 418 nm, a t s u c c e s s i v e s h o r t i n t e r v a l s u n t i l maximum absorbance i s o b t a i n e d . C o n c o m i t a n t l y d e t e r m i n e t h e a b s o r b a n c e s of t h e Assay p r e p a r a t i o n and t h e S t a n d a r d p r e p a r a t i o n i n 1-cm c e l l s a t 418 nm, u s i n g w a t e r a s t h e b l a n k , and s u b t r a c t t h e s e v a l u e s from t h o s e f o r t h e r e s p e c t i v e i r r a d i a t e d s o l u t i o n s , t o o b t a i n t h e c o r r e c t e d maximum a b s o r b a n c e s . C a l c u l a t e t h e q u a n t i t y , i n ug o f C18H2002 i n e a c h m l of t h e Assay p r e p a r a t i o n by t h e formula C(Au/As), i n which C i s t h e c o n c e n t r a t i o n , i n ug p e r m l , of USP d i e t h y l s t i l b e s t r o l RS i n t h e s t a n d a r d p r e p a r a t i o n , and Au and A s a r e t h e c o r r e c t e d maximum absorbances of t h e i r r a d i a t e d Assay p r e p a r a t i o n a n d S t a n d a r d preparation, respectively. De Almedia B a l t a z a r and V e i r a de Arbeu compared d i f f e r e n t methods used i n d e t e r m i n a t i o n of d i e t h y l s t i l b e s t r o l , h e x e s t r o l and d i e n e s t r o l and developed t h e i r own method f o r d i e n e s t r o l (42).

DIETHYLSTILBESTROL

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I n t h e v i s i b l e r a n g e Goodyear e t a 1 ( 4 3 ) made d i e t h y l s t i l b e s t r o l to develop a yellow colour a f t e r i r r a d i a t i o n of a n a q u e o u s a c e t i c a c i d s o l u t i o n of t h e drug w i t h UV l i g h t , and measured t h e c o l o u r a b s o r p t i o m e t r i c a l l y . They a l s o measured t h e c o n c e n t r a t i o n by a b s o r b a n c y d i f f e r e n c e s of a c i d and a l k a l i n e s o l u t i o n s i n t h e UV range. Cheng and B u r r o u g h s u s e d SbC15 i n e t h y l e n e c h l o r i d e t o develop a c o l o u r w i t h d i e t h y l s t i l b e s t r o l and used a c o l o r i m e t e r w i t h f i l t e r s a t 525 and 430 mu (44). They found t h a t t h i s method is more s e n s i t i v e t h a n t h e method of Goodyear e t a 1 ( 4 3 ) . The y e l l o w c o l o u r p r o d u c e d by n i t r a t e d d e r i v a t i v e s of s t i l b e s t r o l and d i e n e s t r o l w i t h a l k a l i had been used by Tokar and Simonyi (45). The p h o t o m e t r i c d e t e r m i n a t i o n of 126 p h e n o l i c compounds i n w a t e r u s i n g group-specif i c r e a g e n t s i . e . p - n i t r o a n i l i n e , s u l f a n i l i c a c i d , 4-aminoa n t i p y r i n e and 3-methylbenzothiazoline-2-ylhydraz i n e , was c a r r i e d o u t by Koppe e t a1 ( 4 6 ) . I n i n j e c t a b l e p r e p a r a t i o n s of l i p i d s o l v e n t , t h e p h e n o l i c hormone w a s e x t r a c t e d w i t h aqueous 0.1 N NaOH and determined s p e c t r o p h o t o m e t r i c a l l y a t 259 nm, while i n t a b l e t s a f t e r d i s p e r s i o n i n d i l . H C 1 and e x t r a c t e d by 0.1 N NaOH and measured a t t h e same wavelength. The a b s o r b a n c e obeyed LambertBeer's law a t c o n c e n t r a t i o n s ranging between 2.5 12.5 ug/ml. The s t a n d a r d d e v i a t i o n f o r i n j e c t a b l e s o l u t i o n s d e t e r m i n a t i o n s was 2.06% w h i l e f o r t h e t a b l e t s was 2.52% (47). 6.32 F l u o r i m e t r i c Methods Ponder ( 4 8 ) determined d i e t h y l s t i l b e s t r o l i n a n i m a l f e e d s ( 5 u g / k g ) f l o r i m e t r i c a l l y by c o n v e r t i n g i t t o p h e n a n t h r e n e d i o l d e r i v a t i v e . The f e e d m a t e r i a l was e x t r a c t e d w i t h a c e t o n e - i s o p e n t y l alcohol ( 1 : l ) a f t e r i n i t i a l treatment with a c e t i c e t h a n d i o l ( 1 :4) mixture. A f t e r p u r i f i c a t i o n acid w i t h s o l v e n t p a r t i t i o n i n g , t h e drug was c o n v e r t e d by UV i r r a d i a t i o n i n t o t h e phenenthrenedione which was t h e n o x i d i z e d t o t h e d i o l and d e t e r m i n e d as p r e v i o u s l y d e s c r i b e d by Umberger e t a l ( 4 9 ) . Ponder (50) a s s a y e d t h e drug and i t s monoglucuronides i n b e e f meat. Vogt d e t e r m i n e d d i e t h y l s t i l b e s t r o l i n t h e f e c e s and u r i n e of f e e d e r c a l v e s ( 5 1 ) .

-


178

K o l i n s k i e t a 1 ( 5 2 ) e x t r a c t e d t h e drug from e n t e r i c - c o a t e d and p l a i n - c o a t e d t a b l e t s , e x p o s e d t o U V i r r a d i a t i o n (pH 6 - 7 ) and t h e r e a c t i o n product t r e a t e d w i t h 2% c a t e c h o l s o l u t i o n i n 2 M H C 1 a t 7OoC and t h e r e s u l t i n g 9,lO diethylphenathrene-3,6-diol was determined p h o t o m e t r i c a l l y a t 4 1 0 nm w i t h e x c i t a t i o n a t 3 3 5 nm. F o r 1 0 d e t e r m i n a t i o n s a t d i f f e r e n t d a y s , f o r 1 mg t a b l e t s , t h e c o e f f i c i e n t of v a r i a t i o n was 0.6% and r e c o v e r i e s w e r e q u a n t i t a t i v e down t o 0 . 1 mg / t a b l e t

.

A f t e r u s i n g ion-exchange column (Amberlite X AD-2) and ( P o l y c o l o r column) followed by L i Chrosorb RP18 column and an on-line r e a c t i o n system, Verbeke and Vanhee (53) f l u o r i m e t r i c a l l y determined s t i l b e s t r o l r e s i d u e s i n u r i n e and animal t i s s u e s . I n t h e on-line r e a c t i o n system o x i d a t i o n was achieved a t 75OC by SO2 i n a l c o h o l i c s o l u t i o n t o form a h i g h l y f l u o r e s c e n t compound, w h i c h , a f t e r e x c i t a t i o n a t 260 nm was measured a t 370 nm and they c o n c l u d e d t h a t t h i s method i s s u p e r i o r t o H. P L. C. methods

.

.

The f o l l o w i n g f l u o r i m e t r i c procedure i s recommended by t h e B.P. ( 4 ) f o r t h e drug t a b l e t s : Procedure Weigh and powder 20 t a b l e t s . To a q u a n t i t y of powder e q u i v a l e n t t o 5 mg of s t i l b e s t r o l add 50 m l of a b s o l u t e e t h a n o l , s h a k e f o r 1 5 m i n u t e s , add s u f f i c i e n t a b s o l u t e e t h a n o l t o produce 100 m l and c e n t r i f u g e . D i l u t e 20 m l of t h e s u p a r n a t a n t l i q u i d t o 50 m l w i t h a b s o l u t e e t h a n o l and t o 25 m l of t h e r e s u l t i n g s o l u t i o n a d d 25 m l o f a s o l u t i o n prepared 1 gram of anhydrous d i p o t a s s i u m hydrogen o r t h o p h o s p h a t e i n 55 m l of w a t e r . T r a n s f e r a p o r t i o n of t h e mixture t o 1-cm c l o s e d q u a r t z c e l l , p l a c e t h e c e l l 1 0 cm from a 1 5 w a t t s h o r t w a v e , u l t r a v i o l e t lamp, and i r r a d i a t e f o r 10 minutes. Measure t h e absorbance of t h e i r r a d i a t e d s o l u t i o n a t t h e maximum a t about 418 nm and c a l c u l a t e t h e c o n t e n t of s t i l b e s t r o l f r o m t h e a b s o r b a n c e o b t a i n e d by r e p e a t i n g t h e o p e r a t i o n w i t h d i e t h y l s t i l b e s t r o l EPCRS.

DIETHYLSTILBESTROL

179

6.4 Polarography

Direct c u r r e n t and a l t e r n a t i n g c u r r e n t p o l a r o g r a p h i c responses of some p h a r m a c e u t i c a l s , i n c l u d i n g e s t o g e n i c compounds, i n a n a p r o t i c o r g a n i c s o l v e n t s y s t e m w e r e i n v e s t i g a t e d by Woodson and Smith (54). The a p p l i c a t i o n of polarography i n s t i l b e s t r o l a n a l y s i s was demonstrat e d by Erb e t a 1 ( 5 5 ) . P u l s e and d i f f e r e n t i a l p u l s e polarography a f t e r i r r a d i a t i o n of t h e drug by U.V. was c a r r i e d o u t by Kubes ( 5 6 ) t o e n a b l e d e t e r m i n a t i o n of t h e compound a s t h e d i k e t o n e , and i t s peak a t -0.8 V (vs the s.c.e) was measured and t h e r e s p o n s e was r e c t i l i n e a r l y r e l a t e d t o c o n c e n t r a t i o n between 0.75 t o 24 u M - s t i l b e s t r o l . 6.5 Chromatographic Methods 6.51 Paper (PLC) and Thin-Layer Chromatography (TLC): The e a r l i e s t of t h e c h r o m a t o g r a p h i c t e c h n i q u e s used i n e s t o g e n i c pharmaceutical p r e p a r a t i o n s was Paper was impregnated paper chromatography (PLC). i n 5% s i l i c o n e i n cyclohexane, d r i e d a t l l O ° C and s p o t s of 5-50 ug of t h e o e s t r o g e n i c compounds were a p p l i e d and descending chromato-graphy was c a r r i e d o u t u s i n g t h e lower l a y e r of t h e mixture: o b t a i n e d by mixing 15 m l of w a t e r , 85 m l of methanol, 30 m l of benzene and 70 m l of hexane a s t h e moving phase ( 5 7 ) . S i l i c a g e l G p l a t e s and i n t e g r a t i n g d e n s i t o m e t r y w e r e c o m b i n e d a f t e r column chromatography i n t h e technique used by J o n e s et a 1 ( 5 8 ) . The s o l v e n t s y s t e m used f o r developing t h e chromatograms was : e t h y l a c e t a t e - l i g h t petroleum - anhydrous a c e t i c acid - ethanol (144:27:20:9). T h y m o p l p h t h a l e i n i n d i c a t o r was s p o t t e d a t RF 1 before s p r a y i n g t h e p l a t e w i t h Folin-Ciocalteu d i l u t e d ( 1 : 4 ) r e a g e n t followed by 0.5 N e t h a n o l i c KOH, u n t i l t h e i n d i c a t o r s p o t was p e r m a n e n t l y b l u e . S e p a r a t i o n of s y n t h e t i c e s t r o g e n s from n a t u r a l e s t r o g e n s was c a r r i e d o u t on s i l i c a g e l H u s i n g chloroform a c e t i c a c i d (85: 1 5 ) ( 5 9 ) . O t h e r s o l v e n t s y s t e m s on T.L.C. were t r i e d by Di b m i z i o and Muscarella (60). Quantitat i o n on s i l i c a g e l G u s i n g two-dimensional chromatography and exposing t h e chromatograms t o 254 nm i r r a d i a t i o n f o l l o w i n g by H2SO4 ( 5 0 % ) and

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180

h e a t i n g a t 95OC was c a r r i e d o u t by Karkosha ( 6 1 ) . High p e r f o r m a n c e t h i n l a y e r c h r o m a t o g r a p h y (H.P.T.L. C. ) u s i n g two-dimensional chromatography u s i n g hexane methylene d i c h l o r i d e ethyl a c e t a t e ( 1 : 2 : 2 ) and c h l o r o f o r m benzene m e t h a n o l ( 3 6 :4: 1) was u s e d , f o r b i o l o g i c a l e x t r a c t s ( f r o m m e a t , l i v e r and u r i n e ) a f t e r p u r i f i c a t i o n by g e l permeation chromatography, by Smets and Verschaeren (62).

-

-

-

Clarke i n h i s monograph ( 2 ) d e s c r i b e d t h e followi n g PLC condition. Sample P r e p a r a t i o n I f t h e s a m p l e i s u r i n e , i t is r e f l u x e d w i t h h y d r o c h l o r i d e a c i d , e x t r a c t e d w i t h e t h e r and t h e e t h e r e a l e x t r a c t is e v a p o r a t e d t o d r y n e s s . R e d i s s o l v e i n e t h a n o l s o t h a t one m l of t h e e t h a n o l i c s o l u t i o n i s e q u i v a l e n t t o 50 m l o f u r i n e . 20 u l of t h i s s o l u t i o n should be a p p l i e d t o chromatogram. Paper Layer: Whatman No.1, a cylinder.

s t a p l e d i n t h e form of

S o l v e n t System: S t r o n g ammonia s o l u t i o n : i s o p r o p r a n o l : water (1:8:1). Equilibration: Development: Location: Rf v a l u e s :

None Ascending

Pauly's

r e a g e n t (yellow).

S t i l b e s t r o l 0.85.

6.52 Gas-Liquid Chromatography (GLC) McGregor e t a 1 (63) a s s a y e d d i e t h y l s t i l b e s t r o l , e x t r a c t e d from u r i n e , u s i n g G.L.C. on a ' c o l u m n of 13.5% polyoxyethylene g l y c o l a d i p a t e on Chromosorb W a t 200'. T h e h o r m o n e was c o n v e r t e d t o t h e d i m e t h y l e t h e r . M o r e t t i e t a 1 ( 6 4 ) derivitized d i e t h y l s t i l b e s t r o l , d i e n o e s t r o l and h e x o e s t r o l a s t h e i r a c e t a t e s and used 3% QF-1 l i q u i d p h a s e a t

--

DIETHYLSTILBESTROL

181

170 OC. The dipropionate of diethylstilbestrol can be determined by direct GLC on 3% JXR on Gas Chrom P at 200°C using stainless steel column. The sample liquid phase was used by Rutherford (65) to determine the cis and trans forms of the estrogenic compound in feeding-stuff pre-mix. The use of a 5% X E - 6 0 o n G a s C h r o m 2 eliminates interference of polyoxyethylene glycol 200 that occurred on 3 % JXR column. The electron-capture G.L.C. of the fluoropropionyl diethylstilbestrol or trifluoroacetic anhydride was successful in determination of concentration as low as 1-2 ppb in animal chew or urine (66,67). The use of columns of OV-17 was described by Kohrman and MacGee (68) and Van de Vaart et a 1 (69) in determinations carried out in biological and cosmetic materials. Clarke in his monograph (2) described the following G.L.C. conditions: Column : 2.5% SE-30 on 80-100 mesh Chromosorb W AWHMDS, 5 ft x 4 mm (i.d.), glass column. Column Temperature : 225OC. Carrier Gas : Nitrogen. Gas Flow Rate : 50 mllminute. Detector : Flame ionization detector (F.I.D.). Hydrogen Flow Rate : 50 mllminute. Air Flow Rate : 300 mllminute. Retention time 0.78 relative to codeine. At a column temperature of 225OC, the relative retention time to codeine (R.Rt) is 0.78. 6.53 High Resolution Liquid Chromatography (H.P.L.C.) and GLC/HPLC HPLC was used by several authors in determination of stilbestrol in various formulations and biological materials. The table summarises some of the HPLC (72-79) conditions of techniques used

Table 4

: Higfrperfomance Liquid chrcooatograply of Diethylstilbestrol.

0.1 M CH3aXNH in MeDH - %O ?3:2) # 7.1, I elution at 1 d/mtn.

Electrockmica1 detection limit cyclic voltamretry at + 0.7V

75%Me(xf

w (254 m),resolved cis

w the

Li chrosorb RP-8 or RP-18

Gradient, lO-lCQ% MeOHorRP-8and 20-100% Me(xf for P 1 8 , 1 ml/m€n.

Zorbax SIL

Et(XHhane (1:39), 1 d/rllin. Gradient elution:A: ~3CN/H20(1:9)

(;N

Ref. (72)

20 Pg

s.e.c.

and trans isorners.

RF2 RP-18 Zork

Lintit of detection

Detection

Mobile #me

_.

0.2-2 j.lg/all

(73)

(74)

W 240 nm. Voltamtry with vitreous - carbon and I - (reference) ~ electrodes, Potential sweep rate is 5 mv/sec.

A

0.01 pg.

0.3-0.5

(75)

ng

(76)

.......

Table contd

B: ~ 3 ~ / H 2 0 ( 9 : 1 ) (25% B a t 0 time t o 45%B a t 5 min). Eluent contains 1 ag of L i C 1 and 1 tlg of LiC104. Ijchrosorb

RP-6

Mec€I : $0 (35: 13) (25:23)

Vitreous carbon or plat& counter electrode and a silvefAgC1 reference electrode. 0.4 ml plasm (78) or urine, 1 g tissue.

RP-8

50% acetonitrile (#I 3.5) 1.5 ml/min.

In-line photochemical reaction, fluorimetrically a t 390 rm (excitation a t 280 m).

lw-ppb levels (79) in U r i n e @.==and

sera extracts.


184

by v a r i o u s a u t h o r s ( 6 6 , 7 0 - 8 2 ) w h i l e combined GLC/HPLC was t r i e d by o t h e r s (66,691. 6.54 Combined Gas Chromatography Spectrometry (GC/MS)

-

Mass

D e t e r m i n a t i o n s of a n a b o l i c s t e r o i d s and d r u g s , i n c l u d i n g s t i l b e s t r o l i n meat and i t s products by combined gas chromatography mass s p e c t r o m e t r y (GC/MS) were done by S t a n and Abraham (83) a n d Duerbeck and Bueker ( 8 4 ) , i n plasma by Gaskell et a 1 ( 8 5 ) , i n u r i n e by Derks e t a 1 ( 8 6 ) , T u i n s t r a e t a 1 ( 8 7 ) D i e d e r i k e t a 1 ( 8 8 ) and i n baby f o o d s a m p l e s by G a l l i e t a 1 ( 8 9 ) . E.I. mass s p e c t r o m e t r y was u s e d by m o s t o f t h e a u t h o r s w h i l e D i e d e r i k et & ( 8 8 ) u s e d n e g a t i v e c h e m i c a l i o n i z a t i o n mass s p e c t r o m e t r y u s i n g CHh OR CH4 : N20 ( 4 : l ) as chemical i o n i s a t i o n reagents. However, GC-MS t e c h n i q u e i s t h e most s e n s i t i v e t e c h n i q u e , o t h e r t h a n R.I.A. methods f o r e v a l u a t i o n of such drugs i n b i o l o g i c a l s , food and p h a r m a c e u t i c a l s and t h e s e n s i t i v i t y of t h e technique i s 0.1 1 ppb.

-

-

-

6.55 Assay by NMR Al-Badr and Ibrahim (90) developed an NMR s p e c t r o m e t r i c method f o r t h e q u a n t i t a t i o n of d i e t h y l s t i l b e s t r o l i n t a b l e t s a n d a m p o u l e s . The m e t h o d i n v o l v e d c o m p a r i n g t h e i n t e g r a l of t h e t r i p l e t system of s t i l b e s t r o l spectrum ( p o s i t i o n e d a t 0.73 O) t o t h a t of t h e s i n g l e t ( p o s i t i o n e d a t 6.25 a ) of m a l e i c a c i d , a s a n i n t e r n a l s t a n d a r d . The p r o c e d u r e f o r t h e q u a n t i t a t i o n of t h e a u t h e n t i c drug, t h e t a b l e t s and ampoules was described. 6.6 Radio Immuno Assay (R.1.A.) R.I.A. methods have p r o v e d t o be t h e most s e n s i t i v e methods of a n a l y s i s today. The t e c h n i q u e i s now a r o u t i n e i n most h o s p i t a l s and a n a l y t i c a l l a b o r a t o r i e s . S u c c e s s f u l R.I.A. of d i e t h y l s t i l b e s t r o l and a l l i e d hormones i n b i o l o g i c a l m a t e r i a l s and e s p e c i a l l y i n none t h i c a l u s e ( i n meat p r o d u c t s ) was shown by s e v e r a l a u t h o r s and t h e s e n s i t i v i t y of t h e technique s u r p a s s e s t h a t of GC/MS method. The s e n s i t i v i t y is i n t h e range - l o w 7 ( 9 1 - 9 6 ) . By t h i s t e c h n i q u e i t was

DIETHYLSTILBESTROL

185

determined i n blood of f e e d l o t c a t t l e ( 9 1 ) , i n animal t i s s u e s ( 9 2 , 9 4 , 9 6 ) and i n f e c e s ( 9 5 ) . A r n s t a d t ( 9 2 ) u s e d t h e enzyme immunoassay method by c o m p e t e t i v e b i n d i n g s t i l b e s t r o l and p e r o x i d a s e d l a b e l l e d s t i l b e s t r o l t o a n a n t i b o d y bonded t o DEAE-cellulose. The method is s u i t a b l e f o r a range a s low a s 0.2 pmol (0.05 ng) of s t i l b e s t r o l . G r i d l e y e t a 1 ( 9 3 ) u s e d a n immunogen a n d a s e c o n d a n t i b o d y of g o a t a n t i - r a b b i t - 0 - g l o b u l i n assay f o r s t i l b e s t r o l and i t s m e t a b o l i t e s i n b o v e i n e l i v e r . T r i t i u m l a b e l l e d s t i l b e s t r o l was used and measurement was c a r r i e d by s c i n t i l l a t i o n counting. 7

METABOLISM D i e t h y l s t i l b e s t r o l can be conjugated i n t h e body w i t h H2S04 t o a s m a l l and v a r i a b l e e x t e n t i n r a t s , c a t s and d o g s b u t n o t i n r a b b i t s (97). Metabolism t o monogluaxmiride by s l i c e s o r r a t l i v e r was r e p o r t e d ( 9 8 , 9 9 ) and a l s o i n t h e e v e r t e d s a c s of t h e r a t i n t e s t i n e (99,100,101 ). Formations of d i h y d r o x y - d i e t h y l s t i l b e s t r o l and t h e methoxy d e r i v a t i v e s i n v a r i o u s s p e c i e s were observed (99,102,103,104). The hormones and i t s m e t a b o l i t e s a r e e x c r e t e d v i a t h e kidney, l i v e r b i l e and f e c e s and f r e e s t i l b e s t r o l p r e s e n c e was o b s e r v e d i n f e c e s examined. McLachlan ( 1 0 5 ) s t u d i e d p r e n a t a l exposure t o d i e t h y l stilbestrol i n mice and observed e q u i v a l e n t amounts i n mother and f e t a l plasma. The c o n c e n t r a t i o n of t h e d r u g i n f e t a l g e n i t a l t r a c t was t h r e e - f o l d h i g h e r t h a n t h a t of t h e plasma.

ACKNOWLEDGEMENT

The a u t h o r s wish t o thank Mr. A l t a f H. Naqvi f o r t y p i n g t h e manuscript. REFERENCES

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527

FLUOXETINE Donald S . Risley Ronald J. Bopp

Lilly Research Laboratories Eli Lilly and Company Indianapolis, Indiana 46285

ANALYTICAL PROF'KES OF DRUG SUBSTANCES VOLUME 19

193

Copyright 0 1990 by Academic Press. Inc. All rights of reproduclion in any form reserved

DONALD S. RISLEY AND RONALD J. BOPP

194

TABLE OF CONTENTS 1 . Introduction 1.1 History 1.2 Name, Formula, Molecular Weight, Structure 1.3 Appearance, Color, Odor 2. Physical Properties 2.1 Melting Range 2.2 Simple SolubilityProfile 2.3 Elemental Analysis 2.4 Infrared Spectrum 2.5 Nuclear Magnetic Resonance Spectrum 2.6 Mass Spectrum 2.7 Ultraviolet Spectrum 2.8 Optical Rotation 2.9 DifferentialThermal Analysis 2.10 Thermogravimetric Analysis 2.1 1 X-Ray Diffraction Analysis

3. Synthesis 4. Analytical Methods 4.1 Chromatography 4.1 1 Thin Layer Chromatography 4.12 High Performance Liquid Chromatography 4.13 Gas Chromatography 4.2 Spectroscopy 4.21 Infrared Spectroscopy 4.22 Nuclear Magnetic Resonance

5. Stability 5.1 Stability in Bulk 5.2 Stability in Dosage Form 5.3 Stability in Solution 6 . Biopharmaceutical Profile 6.1 Pharmacokinetics 6.2 Drug Metabolism 6.3 Toxicity

7. References 8. Acknowledgements

FLUOXETINE

195

1 . INTRODUCTION

1.1 History Fluoxetine hydrochloride is a selective serotonin reuptake inhibitor which is clinically effective for the treatment of depression (1). Fluoxetine hydrochloride formulation is marketed as 20 mg (base equivalent) capsules under the proprietary name Prozac@. Fluoxetine and its major metabolite norfluoxetine act as neuronal inhibitors of serotonin reuptake and result in both increased serotonin concentration at the synaptic cleft and autoreceptor stimulation (2-3). Fluoxetine hydrochloride has been shown to have comparable efficacy to tricyclic antidepressants but with fewer anticholinergic side effects (1,4-6).Fluoxetine hydrochloride has been primarily studied for the treatment of depression, but more recently has been studied for the treatment of bulimia and severe obesity (7-9). 1.2 Name, Formula, Molecular Weight, Structure Chemical Name: d,l-N-methyl-3-phenyl-3-[(a,a,a-m~uoro-p-tolyl)oxy] propylamine hydrochloride. Emperical Formula: C17H1gF3N0.HCI Molecular Weight: 345.79 Structure:

1.3

Appearance, Color, Odor

Fluoxetine hydrochloride is a white to off-white, crystalline, odorless powder.


196

2. PHYSICAL PROPERTIES 2.1 Melting Range

The melting range of fluoxetine hydrochloride is 158.4 - 158.9OC 2.2 Simple Solubility Profile

The solubility properties of fluoxetine hydrochloride are listed in Table I. Fluoxetine hydrochloride is freely soluble in methanol and ethanol; soluble in acetonitrile, chloroform, and acetone; slightly soluble in ethyl acetate, dichloromethane, and water (with sonication at p H 1.2,4.5, and 7.0). The maximum solubility of fluoxetine obtained in water is 14 mg/mL. Fluoxetine is essentially insoluble in toluene, cyclohexane, and hexane. Table I. The Solubility Properties of Fluoxetine Hydrochloride.

2.3

Solvent

Solubilitv (mdrnL)

Methanol Ethanol Acetone Acetonitrile Chloroform Dichloromethane Water (PH 1.2) (PH 4.5) (PH 7.0) Ethyl acetate Toluene Cyclohexane Hexane

> 100 > 100 > 33 c 100 >33c100 > 33 c 100 >5c10 >1111 2 c 2.5 > 0.5 c 0.67 > 0.5 c 0.67 > 0.5 c 0.67

Elemental Analysis

The elemental analysis data for a typical sample of fluoxetine hydrochloride are listed in Table II.

FLUOXETINE

197

Table 11. Elemental Analysis of Fluoxetine Hydrochloride.

96 Calculated

Element

59.05 5.54 16.48 4.05 4.63 10.25

C H F N 0

c1

!zLEaBd 59.26 5.68 16.52 4.05 4.81 9.93

2.4 M a r e d Spectrum The infrared spectrum for fluoxetine hydrochloride in a KBr pellet as obtained on a Mattson Nova Cygni infrared spectrophotometeris illustrated in Figure 1. The major absorption bands for both the infrared and the Raman frequencies and the corresponding assignments are listed in Table III. Table III. Infrared and Raman Spectral Assignments for Fluoxetine Hydrochloride. Frequency (cm -')

Infrared

Correlations/Assignments OH stretch - H20 in KBr

3430vb

3085,3060 3039,3026 3010

3114,3087 3064,3043 3011

Aromatic CH stretches

2986,2957 2927,29 16

2989,2969 2962,2949 2937,2918

Asymmetric CH2 and CH3 stretches

2884,2861 2838

2893,2870 2843,2825

Symmetric CH2 and CH3 stretches

2805,2790 2772,2730 2638,2614 2547,2490 2435

2800,2769 2746,2700 2627,2609 2547,2495 2458

NH2+ - NH stretches and 'combination bands'

1636

1636

NH2+ deformations


198

Table III. (Continued)

Infrared

Raman

1614,1589 1585, 1516 1495

1615, 1605 1588

Phenyl ring vibrations

1474,1470

1479, 1470

CH2 deformations

1455, 1446

1445

Asymmetric CH3 deformations

1429

1429

Symmetric CH3 deformations

1329

1326

CF stretches

1314, 1307

1306


1257, 1241

1259, 1244

C-0stretches; aryValky1 ether

1182, 1161

1185, 1155

CF stretches; CN stretches

1122,1108

1116

C - 0 stretches; aryValkyl ether

1075,1069 1028, 1023

1079,1070 1029


999

1003

Ring 'breathing' vibrations mono-substituted phenyl

991,959 948,916 907, 848 819

Phenyl CH wags

783

Phenyl ring vibrations Para di-substituted

768,747 735


986, 945, 903, 841,

957 913 847 818

765,746 730

secondary amine.

FLUOXETINE

199

Table III. (Continued)

Infrared

R&tUB

647, 635 622

651,638 622

697

Phenyl ring vibrations mono-substituted Phenyl ring vibrations

Unassigned: Infrared: 3225,3173,2355, 1970, 1951, 1907, 1897, 1886, 1808, 1010, 878, 858, 805,671,594,563, 520, 512 Raman: 3225,3202,3170, 1690, 1391, 1358, 1275, 1211, 1099, 1040, 881, 569, 515, 478,414, 363, 306, 294, 281, 261, 215 2.5

Nuclear Magnetic Resonance Spectrum

The proton magnetic resonance of fluoxetine hydrochloride is represented in Figure 2. The spectrum was obtained on a General Electric QE 300 MHz NMR using CDC1, as the sample solvent. Proton chemical shifts were determined from the two-dimensional l3C/lH correlation data. The 13C spectrum is shown in Figure 3. Structural assignments are listed in Table IV.

6

5

13

2.5 100-1

3.0 I

3.5 4.0 I

I

5.0 I

Microns 6

8

10

15

20

I

I

I

I

I

40 I

Infrared - KBr Pellet

30-

Raman - solid

2010-

0 i ~ - . r l- .l -, v . - l l . . ,m .~ l l ~. ,, .. ll .. ,, .. ll .. ll .. ll .. ,, .. ll .. ll .. ll .. ,, ~~ ll ~~ ,,. ,~~ .l l ~~. ,, , .~~ . , . 4000 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 600 400 21 Wavenumber 4 Figure 1. The infrared spectrum offlruoxeetine hydrochloride in a KBrpellet.

201

a

-

-ru

- m

-

-Lo

-10

-r.

- m

-m

I

1 ~ " ' ~ " " 1 " " ~ " " I " " ~ " " I " " ~ " " 1 " " ~ " " 1 " " ~ " " 1 " " ~ " ~ ~ ~ " ~ ~ " ~ ~ ' l 140 120 100 80 60 40

160

Figure 3. The I3C NMR spectrum ofjluoxetine hydrochloride in CDC13.

20

PPM

FLUOXETINE

203

Table IV. The NMR Spectral Assignments for Fluoxetine Hydrochloride. Assignment

1 2 3 4 5, 9 6, 8 7 10 11, 15 12, 14 13 CF3 N-CH3 Exchangeables

*3C (A)

~~

3.12 2.48 5.47

46.03 34.49 77.04 139.72 125.76 126.77 123.33 159.74 115.88 128.99 128.38 124.21 32.89

6.90 7.39 7.31 7.27 7.24 2.62 9.7 1

2.6 MassSpectrum The electron impact @I) mass spectrum of fluoxetine hydrochloride is illustrated in Figure 4. The spectrum was obtained using a Varian-MAT 73 1 MS. The EI spectrum for fluoxetine hydrochloride shows a main contribution from the base (MW=309). The EI spectrum is dominated by a major fragmentation from CHz=NH-CH3+at m/z 44. Several other fragmentationsare illustrated in Figure 5 and listed in Table V.

+*

-N

/H

. HCI

44

Figure 5. Electron impactfragmentation schemefor fluoxetine hydrochloride.

100-44 95 -

9085 80. 75 70 656055~

5045 40 35 ~

~

3025 2015105-

0Figure 4. The EI mass specnun offluoxen'ne hydrochloride.

FLUOXETINE

205

Table V. The Mass Spectrum Fragmentation Assignments for Fluoxetine Hydrochloride.

44 59 77 91 104 148 162 25 1

CH2=NH-CH3+ MeNHEt+ Ph+ Ph-CH2' Ph-CH=CH2+ Ph-CH-CH2-CH2-NHCH3' CF3-Ph-O+ [M-MeNH(CH)2]+

The field desorption (FD) mass spectrum obtained at the optimum anode temperature consists of the molecular ion of the base at d z 309 and the protonated f o m of the base at m/z 310. A small fragment peak is present at m/z 104. At higher current emissions, both base and protonated base forms are observed along with cluster ions (base + salt + H) at d z 655 and (base + 2x salt + H) at d z 1000. Cluster ion formation is often observed in a FD spectra due to ionization in the condensed phase. 2.7


The ultraviolet spectrum of fluoxetine hydrochloridein methanol is shown in Figure 6. The ultraviolet absorbance of fluoxetine hydrochloride is due to individual contributionsfrom CF3-Ph-OR and Ph-R. The maximum absorbance from the fluoronated cresol chromophore occurs at 227 nm with a molecular absorptivity of E = 12,900. The peak absorbances are listed in Table VI. Table VI. Peak Absorbances for Fluoxetine Hydrochloride. Wavelength hm) 227 264 268 275

E 1%/1 (cm) 372.0 29.2 29.3 21.5

E

12,900 1,010 1;010 745

0 C Q

e 1.286 -

2

-

.633-

.ooo -

~L~.""""'"'

L-LII.LI_L_L-JIIL

Figure 6 . The W spectrum offluoxetine hydrochloride in methanol.

L-u

1

FLUOXETINE

207

2.8 Optical Rotation The observed rotation for a 10 m g / d methanol solution of fluoxetine hydrochloride using the sodium D-line on a Perkin-Elmer 241MC Polarimeter was determined to be O.OOo indicating a racemic mixture. 2.9 Differential Thermal Analysis The DTA thermogram for fluoxetine hydrochloride, at a heating rate of 5OC per minute, shows a sharp endotherm at 161OC indicating a melt. A large exotherm occurs at 241OC and this is attributed to the decomposition of fluoxetine. 2.10 Thermogravimetric Analysis The TGA thermogram for fluoxetine hydrochloride, at a heating rate of

S0Cper minute, shows an initial weight loss at 172°C followed by continuous weight loss indicating decomposition. 2.1 1 X-Ray Diffraction Analysis Listed in Table VII are the data from the powder X-ray diffraction for fluoxetine hydrochloride where h=1.5418,d is the interplanar spacing (A), and IRo is the relative intensity of the X-ray line. Figure 7 illustrates the Xray diffraction.

3. SYNTHESIS The schematic diagram for the synthesis of fluoxetine hydrochloride is outlined in Figure 8. Synthesis of fluoxetine began with a-[2-(Chloro)ethyl]benzene methanol. A Finkelstein reaction was performed to yield the corresponding iodo derivative. Reaction of this iodide with aqueous methylamine resulted in formation of a-[2-(Methylamino)ethyI]benzene methanol. This material was then reacted with sodium hydride in dimethylacetamideto generate the alkoxide. Addition of 4-fluorobenzotrifluoride led to a facile nucleophilic substitution. Fluoxetine was then reacted with dilute hydrochloric acid to produce the hydrochloride salt (10).

DONALD S . RISLEY AND RONALD J. BOPP

208

Table VII. X-ray Powder DiffractionData for Fluoxetine Hydrochloride.

do

UQ

31.43 16.14 8.73 8.09 6.7 1 6.38 6.09 5.39 4.94 4.87 4.79 4.62 4.37 4.27 4.2 1 4.04 3.92 3.77 3.75 3.59 3.53 3.47 3.36 3.29 3.23 3.19 3.09 3.05 2.99 2.92 2.75 2.57

0.7 1 0.66 0.07 0.04 0.02 0.60 0.04 0.90 0.03 0.03 0.21 0.01 0.14 0.06 0.01 1.oo 0.04 0.15 0.11 0.02 0.06 0.01 0.01 0.01 0.1 1 0.09 0.21

0.01 0.01 0.01 0.09 0.01

400 -

350;

300y 2501

i

200 -

150 100;

50 ; Fp

5.0

10.0 Figure 7 . The X-ray difiraction offluoxetine hydrochloride.


210

H

H 0

0

a-[2-(Methylamino)ethyl]benm1emahano1

NaH,Dimethylacetamide

cF3

a

cF3 Fluoxetine

+

HCL

+

0

a 0

HQ

Fluoxetine hydrochloride

Figure 8. The chemical synthesis offluoxetine hydrochloride.

211

FLUOXETINE

4. ANALYTICAL. METHODS 4.1 Chromatography 4.1 1 Thin Layer Chromatography A thin layer chromatography (TLC) method can be used to determine the identity and purity of fluoxetine hydrochloride. Precoated 20x20 cm silica gel 60F254 TLC plates are used in combination with a binary solvent system consisting of 90% methanol and 10% concentrated ammonium hydroxide. Visualization is performed by exposing the plate to iodine vapors prior to viewing under short W light (254 nm). This system will separate the starting material and synthetic intermediatesfrom fluoxetine hydrochloride. These compounds and their respective Rfvalues are listed in Table VIII.

Table VIII. Thin Layer Chromatography for Fluoxetine Hydrochloride. ComDound

Ef

Acetophenone

0.84

Starting Material

Benzylmethylamine

0.58

Starting Material

p-Chlorobenzomfluoride

ND

Starting Material

Paraformadehyde

0.38-0.61 (streak)

Starting Material

a-(N-methyl-N-benzylamino)propiophenone hydrochloride

0.55 to (solvent front)

Intermediate

a-[2-(Methylamino) ethyllbenzene methanol

0.3 1

Intermediate and Degradation Product

Fluoxetine hydrochloride

0.58

New Drug Substance

N-Methylbenzenepropanamhe

0.34

Possible Impurity

p-Trifl uorometh ylphenol

0.86

Degradation Product

Identity

212

DONALD S. RISLEY AND RONALD 3. BOPP

4.12 High Performance Liquid Chromatography A high pexformance liquid chromatography (HPLC) method is used for quantitation of fluoxetine hydrochloride at the 0.001% to 0.03% level in rodent feed. The mobile phase consists of 55% methanoV45% water/O.5% diethylamine (water and DEA pH adjusted to 7.4 with phosphoric acid). Chromatographicconditions include a Supelcosil LC8 (150mm x 4.6mm) column combined with a porous silica gel pre-column and packed C8 (pellicular bead) guard column. A flow rate of 1.6 W m i n is used with UV detection at 227 nm. Fluoxetine is extracted from feed using methanol as the extraction solvent. The feed sample and methanol are vigorously shaken for 40 minutes on a wrist-action shaker. A portion of the extraction solution is filtered through fluted filter paper, eluted through an alumina column, and is evaporated to dryness. The residue is reconstituted with mobile phase, and filtered through Whatman #1 filter paper prior to injection. A reversed-phase HPLC system has been developed to determine fluoxetine in capsule and tablet formulations. The mobile phase consists of 50% acetoninile/49%water/l% triethylamine (water and methylamine adjusted to pH 6 with phosphoric acid). A DuPont Zorbax RX column (250 mm x 4.6 mm id.) is used for the separation. The flow rate is 1.0 mL/min and UV detection is at 260 nm. The samples are prepared by emptying the contents of a capsule or adding a tablet to a 50 mL volumetric flask, diluting with 40 mL of mobile phase, and sonicating the mixture for five minutes. The sample is cooled and diluted to volume with the mobile phase. This solution is centrifuged for five minutes prior to injecting the Supernatant. A reversed-phase HPLC system can be used for the quantitation of fluoxetine and norfluoxetine (y-[4-(t1ifluoromethyl)phenoxy]benzenepropanamine) extracted from serum. The assay is linear for these two compounds over the concentration range of 25-800 ug/mL (1 1). An alternate reverse phase HPLC method can be used for the determination of these two compounds in plasma by an extraction procedure into hexane (12).

4.13 Gas Chromatography Due to the reasonable thermal stability and the volatility of fluoxetine, a gas chromatography (GC) method has been used to determine fluoxetine in dosage forms. The chromatographic method was developed on a HewlettPackard model 5710 gas chromatograph. A 15 m x 0.53 urn x 1.5 um DB-1 Megabore column (J&W Scientific) is used with an oven temperature of 17OOC. The injection port temperature is 275OC and the FID detector temperature is 25OOC. Helium flow rate is 25.0 mL/min, oxygen flow rate is 300 a m i n , and hydrogen flow rate is 40 mL/min. This procedure involves extraction from basic solution into chloroform. The chloroform extract is filtered through Whatman #1filter paper prior to analysis.

FLUOXETINE

213

A GC method is used for the quantitation of related compounds and raw materials of fluoxetine hydrochloride. Optimized conditions are as follows for a Hewlett-Packard model 402 gas chromatograph with a flame ionization detector. The column is 3 ft. x 1/8" i.d. glass packed with 4% OV-225 on 80/lOO mesh AWDMCS Chromosorb G. Oven temperature is maintained at l8O0C, the injection port temperature is maintained at 245OC, and the detector temperature is 265°C. Gas flow rates are 300 mL/min for oxygen, 60 mL/min for helium, and 40 mL/min for hydrogen. N-pentacosane (0.8 mg/mL) in chlorofomi is used as an internal standard. All available precursors, intermediates, impurities, and degradation products were analyzed according to this method; the compound names and approximate retention times are listed in Table IX. A GC method is used for the quantitation of fluoxetine and norfluoxetine in plasma, urine, and tissues. This method requires the formation of the PFB derivative prior to analysis. Conditions were optimized using an HP model 5713 GC with electron capture detection (13). An alternate GC-ECD can be used for the determination of these two compounds in serum (14). 4.2 Spectroscopy 4.21 Infrared Spectroscopy Fluoxetine hydrochloride is mixed with potassium bromide. The mixture is pressed into a transparent pellet and a spectrum is recorded with a suitable infrared spectrophotometer. This infrared spectrum is used for identity confirmation when it compares favorably to a reference standard spectrum run under similar conditions. Alternatively, the infrared spectrum for fluoxetine (free base) can be identified after extraction from a basic solution into chloroform. Positive identification is made when the sample spectrum compares favorably to a reference spectrum obtained in the same manner. 4.22 Nuclear Magnetic Resonance Fluoxetine hydrochloride is added to a nuclear magnetic resonance sample tube and dissolved in deuterated chloroform and a small aliquot of tetramethylsilane. A reference standard spectrum is obtained in the same manner. Positive identification occurs when the chemical shifts and integral values of the sample compare favorably to the reference spectrum.


214

Table IX. Gas Chromatography for Fluoxetine Hydrochloride.

ComDound

ComDound Use

Retention (min)

p-Chlorobenzotrifluoride

Starting Material

c0.5

3-Nitro-4-trifluoromethylphenol

Intermediate

1 mg of folic acid was shaken for 30 minutes with O.1M-HC1 (25ml) aquous, 3% calcium lactate aquous, 8% Na3P04 (1:l) buffer (225 ml) was added, and the mixture was heated at 50' for one or (for slow release tablets) A 20ml portion of the two hours and filtered. filterate was adjusted to pH 6.8 to 7.5 with aquous 10% ascorbic acid and after purging the solution with N 2 , a polarogram was recorded from -0.4V (vs. the s,c.e); 5ml of a standared folic acid solution was then added and a second folic acid was calculated from

FOLIC ACID

247

a given equation. The sensitivity of he method was about 0.1 ug ml-1 for a diffusion current of 1 nA, and accurate and reproducible results were obtained for 1.39 to 1.74 mg of folic acid. 2. Jozan et a1 (35) studied a method that a solution of the tablets in alkaline Na citrate solution (pH 12) w a s analyzed directly by polarography. Although insoluble additives interefered, their effect was constant for contents upto about 30%. The polarogram was recorded from -250 to -1050 mV (vs. the s.c.e) for folic acid. The half-wave potential (mV) was -483.

3. Folic acid in pharmaceutical preparations can also be determined polarographically. Dissolve one tablet (containing 30-60ug of folic acid, and usually Fe salts) in lOml of 0.15 M- diethylenetriamine - N N N N’N”- penta acetic acid (disslve 60 g of the acid in NaOH, adjust the pH to 8 and dilute to 1:l) and dilute to 50 ml with O.1M-acetate buffer of pH 5.5. De-aerate 20 ml portion with N 2 , record on a.c. polarogram. (use of a phase-sensitive 8.c. polarograph improves the sensitivity substantially), measure the peak height, and determine the folic acid content by use of a calibration graph (rectilinear over the range 20 nm to20 pm if a phase-sensitive a.c. polarograph is used) or by the standard, addition method. (36).

4. W.J. Mader et a1 (37) estimated folic acid polarographically except when iron is present with 1% tetramethylammonium hydroxide solution, pH 9.0 to9.5, as the base solution, it has a half-wave potential verses the S.C.E. of 0.98 volt with cadmium as an internal standard, the error of the estimation is 2%. (38) 0

8.6

Pluorimetric Method

1. U. Hla. Pe. eta1 describes the method for urinary folic acid. Urine is collected for 5 hours after administration (oral or intramuscular) of 5mg of folate, and an aliquot adjusted to pH 3 . 5 is applied to a column of activated A1203 equilibrated with 0.2 M-acetate buffer of pH-4. After washing the column with buffer solution, the folic acid is eluted with saturated NazB407 solution and the fluorescence is

FAHAD JABER AL-SHAMMARY ETAL.

248

developed by IZMn04 oxidation (decolorising with HzOz ) and measred at 470 nm (excitation at 365 nm). (38). 2. The fluorimetric determination of folic acid has been examined. On oxidation with K h 0 4 it is converted in to 2-amino-4-hydroxypteridine-6-carboxylic acid which flourescence strongly at 470 nm. When irradiated with light of wave-length 365 nm; the intensitiy of the fluorescene is proportional to the concentration. When interfering pigments are present, the oxidation product is isolated chromatographically. ( 3 9 ) . 8.7

Radio-Assap

1. Serum folate was estimated by Dunn et al. (40). The serum was heated on a boiling water bath with lysin buffer solution of pH 10.5 to destroy the binding capacity of protein, then the mixture is diluted with L3H1 folate, B-lactoglobulin solution is added and after 45 minutes, the free and bound forms of folate are seperated by centrifugation with haemoglobin-coated charcoal; the supernatent solution is analysed for 3 H by a liquid scintillation technique.

2, In an other method a partially purified folate binding preparation from hog-kidney is incubated with serum and tritiated p t e r y l g l u t a m a t e in phosphate-ascorbate buffer, pH 7.6, at 4°C for 30 minutes in dark. Free tritiated pterylglutamateis removed by the addition of cold, albumin-coated charcoal suspension and centrifugation. Free and bound labelled pterylglutamate is measured by scintillation counting. (41).

In this method the assay of folic acid in plasma 3. is based on inhibition by folic acid of the binding of 3H-labelled folic acid to a folic acid specific protein obtained from milk. A commercial test kit is used and reproducible results were obtained in 600 assays on plasma from healthy men and women receiving tablets each containing 0-25 mg of folic acid. Results f o r normal subjects not receiving folic acid ranged from 3.2-20.2 ng ml-l (average 6.8 ng ml-1 ) . This procedure is suitable for differenciating between anaemias due to deficiency of cyanocobalamin and of folic acid. (42).

FOLIC ACID

249

4. Smultaneous radio-assay of serum vitamin Biz (cyanocobalomin) and folic acid was done by Gutcho et al. The procedure describes €or determining both these vitamins in same 100 p1 portion of serum. (43). 5. Hendel eta1 used the method in which antiserum was raised in rabbits immunised with a conjugate of folic acid and methylated bovin serum albumin. Erythrocytes and plasma samples were diluted with buffer solution and heated, the mixture were centrifuged and the supernatant solution were used in the assay; urine was assayed directly. The antiserum and sample were incubated for 2 hours at 4 " with [3H] folic acid. Poly ethylene glycol was added in the mixture, centrifuged, and the radioactivity of the precipitate was measured by liquid scintillation counting. (44). 6. Folic acid was also measured in human plasma and erythrocytes. Samples were homogenized with 0.05 M. phosphate buffer (pH 6.1) containing ascorbate. The homogenates were treated with chicken pancreas confugase and incubated for 2 hours at 37" and the enzyme action was stopped by heating the vessel in a boiling water bath. Folic acid was then determined by the radiometric and turbidmetric method. (45).

Waxman et a1 (46) also studied the serum folate levels and serum folic acid binding protein by 3H-PGA (tritiated pterylglutamic acid) radio-assay.

7,

8.8

ChroratoptraDhic Methods 8.8.1

Colurn ChroBatouraDhp

Plasma folate compounds can be seperated from antibiotic and hypnotics by applying a sample solution in an agous NaCl to a column (10cm x 10mm) of TEAE-cellulose (cellex T. calbiochem) and carrying out gradient elution by allowing 0.5M-phosphate buffer of pH 6.5 to drip from an overhead container into a mixing chamber containing 500 ml of H2O at 2 ml per minute while the elute leaves the column at the same rate. Folate is completely seperated from the other compounds, which appear in the first 401111of elute, the folate present, apears later, in the 160 to 2401111 fraction. (47).

FAHAD JABER AL-SHAMhlARY ETAL..

250

8.8.2

Thin layer chromatojcraDhy (TLC)

A summary of some of the TLC systems investigated for the analysis of folic acid are given in the table (4). 8.8.3

u h Performance Liauid ChromatoRraDhp 1HPLC 1

The different methods used to determine folic acid by HPLC are summarised in the table (5).

8.9

Thermal Anelssis (DSC)

A differencial scanning calorimetry curve of folic

acid was obtained Fig (8) on a Perkin-Elmer DSC-2c differencial calorimeter. Nitrogen was used as the purge gas. Scan was performed at the rate of 25"C/min. from 60-380°C. The DSC curve revealed an endothermic melting peak (Max. 193.38'C). 9.

Acknonledrtements The authors appreciate the technical services extended by Mr. Babkir Awad Mustafa, College of Applied Medical Sciences, King Saud University, Riyadh. The authors are also very much thankful to Mr. Tanvir A . Butt, College of Pharmacy, King Saud University, Riyadh for typing the manuscript.

10.

1.

References "The Merck Index" 10th ed. Merck and Co, Inc., Rahway, U.S.A. (1983).

N.J.

2.

The British Pharmacopoeia" Her Majesty's Staionary Office, London Vol. I (1980).

3.

"The United States Pharmacopeia". 19th ed. , Mack Publishing Company, Easton, PA (1975).

4.

"Martindale" , The Extra Pharmacopea" 28th ed. Eds. The Pharmaceutical Press London (1982).

5.

"Clarks Isolation and Identification of Drugs" The Pharmacetical Press London, 2nd ed. 1986.

Table (4): Summary of conditions used f o r the TLC of folic acid.

Plate

Developing solvent

Detection

Cellulose powder

Butanol: acetic acid: water ( 4 : 1 : 5 )

254 nm

-

Silica gel

Propanol: 10% aq. NH3 glycerol ( 4 : l : l ) for 2 hours.

Greenyellow spot

10% cuso4 solution 2% aq. NH3 (5:l).

Silica gel G 0 . 2 5 mm

Butanol: acetic acid: ethano1:water ( 2 5 0 : l : 100: 125 1.

550 nm

3% aq. Na2HFQ4 ( 6 ml)

Kiesel gel G

Acetic acid: butanol : HzO (1:4:5)

tiV

G

Extd. solvent

Rf

Ref.

0 . 1 at conc. > 1 Pg Per P1 and 0 . 4 2 at conc. of 0 . 5 Pg

48

0.41

49

50

51

Table (5) Summary of HPLC conditions for the determination of folic acid

Column

Mobile phase

Flow rate

(30 cm X 4 me) packed with p Bonda pak C i 8 (10 pm)

5 OlM tetrabutylammonium phosphate in aq. 30% methanol

1 ml/min

p Bondapak

Acetonitile: 0.1 M Na. acetate buffer pH 5.7 (3:47)

c18

Stainless steel (30 c m x 4 m id) packed with p Bondapak cl8.

[ (NaC104.H20 35.1 g ) ] , [K2HW4 (1.36 g ) ] , [N.KOH (6.94

ml)] and [CHziOH (40 ml)] diluted to 1 L with H2.

Sample

-

Nutritional diet

-

Detection

Ref.

254 nm

52

365 nm

53

254 nm

54

Continued (Table 5)

...

Analytical column (30 cm X 4 ram and guard column (5 cm X 4 mm) contained Ci s bonded phase.

Amm. phosphate buffer solution

(30 cm X 4 of p Ekmdapak CIS

[Tetrabutylamm. hydroxide (7.5 ml of aq. 40% solution)]H Z w 4 (2.04 g)[H3P04 (4 ml of 3N)][methanol (240 ml)]Hz0 (to 11) as mobile phase of pH 7.0.

Silica gel C18

Methanol: 4 mM Na heptane sulphonate in aq. 2% acetic acid (1:9).

Reversed phase column

0.05 M KHZPO4-0.25 M NaC104 buffer pH 7.2.

lam)

-

1.5 ml/min

-

254 nm

55

Multivitamin

280 nm

56

Multivitamin

280 nm

57

-

254 nm

58

......................... Continued

/...

Continued (Table 5)

...

Ultraspher 1P and p Bondapak phenyl

Phosphate buffer solution (pH 2.3) containing acetonitrile.

-

Pre-column (5 cm X 3 aa) of P Bondapak phenyl/ Corasil (30 w).

0.042 M-NaC104, 1.5 nM-KH2pO4 and 1.6% of methanol adjusted to pH 7 with 1M-KOH

-

Selected food

Fluorescence

59

280 nm

60

255

FOLIC ACID

FOLIC ACID 3.22 q

YTI

SCAN RATG

PEAM

25.00 dig/rtn

144.5 213.0 17874

Fw))c

P(BET1

m

L.

I

TEMPERATURE (C>

FILGGS#KD4

DATG

98/81/23

TIME1

0053

Fig. 8 : D i f f e r e n c i a 1 Scanning Calorimetry Curve o f F o l i c A c i d

FAHAD JABER AL-SHAMMARY ETAL.

256

6,

Remington's Pharmaceutical Sciences". 5th ed., Mack Publishing Company, Easton, Pennsylvania, (1975).

7.

Atlas of Spectral Data and Physical Constants for Organic Compounds. J.C. Grasselli and W.M. Ritchy, 2nd Ed. p. 332 CRC Press Inc., Cleavland, Ohio (1975).

8.

"Drug Information 88". Pharmacists.

9.

B.L. O'Dell and A.G. Kline, J. Biol. Chem. 149, 323 (1943).

10,

E.P. Daniel and O.L. Kline, J. Biol. Chem. (1947).

11 *

American Society of Hospital

170, 739

E.L.R. Stokstad, D. Fordham and A . de Grunigen, J. 167, 877, (1947).

--Biol. Chem.

12.

O.H. Lowry, O.A. Bessey and E.J. Crawford, J. Biol. Chem. ,180, 389, (1949).

13.

H.K. Mitchell, E.E. Snell and R.J. Williams, J. Amer. Chem. SOC, 63, 2284 1941.

14.

P.R. Burkholder, I McVeigh and K. Wilson, Arch Biochemi., 1, 287 (1945).

15.

Mohammad Saleem Mian, College of Pharmacy, King Saud University, Riyadh, Personel Communication (1990).

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J-

ANALYTICAL PROFILE OF LOBELINE HYDROCHLORIDE

Farid

3.

Muhtadi

Department of Pharmacognosy, College of Pharmacy, King Saud University Riyadh , Saudi Arabia

.


261

I

Copyright 0 1990 by Academic Press. Inc. All rights ofreproduction in any form resewed.

FARID J. MUHTADI

262

LOBELINE HYDROCHLORIDE CONTENTS ---_____

1. Description, 1.1 1.2 1.3 1.4 1.5

Nomenclature Formulae Molecular Weight Elemental Composition Appearance, Color and Odor.

2. Physical Properties. 2 . 1 Melting Range

2.2 2.3 2.4 2.5 2.6 2.7 2.8

Eutectic Temperature S o l u b i l i t y Data pH Range S p e c i f i c Optical A c t i v i t y Crystal S t r u c t u r e X-Ray Powder Diffraction Spectral Properties 2.8.1 2.8.2 2.8.3 2.8.4

U l t r a v i o l e t Spectrum Infrared Spectrum Nuclear Magnetic Resonance Spectra Mass Spectrum.

3. Isolation of Lobeline,

4. Structure of Lubeline. 5. Synthesis of Lobeline. 6. Biosynthesis of Lobeline.

7. Pharmacology. 8. Methods of Analysis. 8.1 8.2 8.3 8.4 8.5 8.6

Identification Microcrystal Formation T i t r i m e t r i c Determinations Gravimetric Determinations Polarographic Methods Spectrophotometric Methods

LOBELINE HYDROCHLORIDE

8 . 6 . 1 C o l o r i m e t r i c Determinations 8 . 6 . 2 UV Determinations 8 . 6 . 3 T u r b i d i m e t r i c Determinations 8 . 7 Chromatographic Methods 8.7.1 8.7.2 8.7.3 8.7.4 8.7.5

Paper Chromatography Thin Layer Chromatography Gas Liquid Chromatography High Performance Liquid Chromatography Ion Exchange R e s i n s .

References & Acknowledgement.

263

FARID J. MUHTADI

264

1. Description 1.1 Nomenclature 1.1.1

Chemical Names 2- [ 6- (2-Hydroxy-2-phenylethyl)- 1-methyl2-piperidinyl]-1-phenylethanone. 2- [ 6-(8-hydroxyphenethyl)- l-methyl-2-piperidyl] acetophenone. 2-(2-Hydroxy-2-phenylethyl)-N-methyl-6-phenacyl piperidine. Ethanone 2- [ 6- (2-hydroxy-2-phenylethy 1) - 1methyl-2-piperidinyl]-l-phenyl-, [2R-[2a,6a (S*)

11.

Names of the acids f o h n s the s a l t s are added a f t e r the chemical names e.g. 2- [6-(8-hydroxyphenethyl)-1-methyl-2-piperidyl] acetophenone hydrochloride.

1.1.2

Generic Names Lobeline hydrochloride; Alpha lobeline hydrochloride; a-Lobeline hydrochloride; Inflatine hydrochloride.

1.1.3

Trade Names Lobron; Zoolobelin (for the hydrochloride) Bantron; Glenden; Habit-X; Lobatox; Lobeton; Lobidan; Toban o-t-c; unilobin (for the sulfate).

1.2

Formulae 1.2.1

Empirical C22H27N02 C22H28C1 NO2 C44H56N208S

1.2.2

(Lobe1ine) (Lobeline hydrochloride) (Lobeline sulfate)

Structural Lobeline is one of the pyridine-piperidine alkaloids. Its chemical structure was proposed by Wieland and co-workers (1-3) and has been confirmed by the total synthesis of the

265


alkaloid, which was first carried out by the same group (2-5) and later by others (6-10).

C"3

1.2.3

CAS Registry Number [ 90-69-71 Lobe1ine [134-63-41 Lobeline hydrochloride [134-64-51 Lobeline sulfate

1.2.4 Wiswesser Line Notation (11) T6NTJ A BlYQR 6 FlVR *LV (Lobeline). T6NTJ A BlYQR FlVR *LV G GH (Lobeline hydrochloride). 1.2.5

Absolute Configuration The absolute configuration of natural (-) lobeline and of (+)-lobeline were deduced from chemical degradation, synthesis and corelation (12,13). The configuration of natural ( - ) -1obeline was established as (25, 6R, 8 5 ) -8,lO-diphenyllobelionol (12). The configuration of racemic lobeline was determined as (25, 6R, 8s)-8,lO-diphenyllobelionol and its enantiomer (2R, 65, 8R)-8,10-diphenyl-lobelionol (13). The abso Zute configuration of (-1 -lobe line is shorn above.

FARID J. MUHTADI

266

1.3

Molecular Weight 337.47 373.92 773.0

(Lobeline) (Lobeline hydrochloride) (Lobeline sulfate)

1.4 Elemental Composition Lobeline : C, 78.30%; H, 8.07%; N , 4.15%; 0 , 9.48%. Lobeline hydrochloride : C, 70.67%; H, 7.55%; C1, 9.48%; N, 3.75%; 0, 8.56%. Lobeline sulfate : C , 68.37%; H, 7.30%; S, 4.15%; N , 3.62%; 0 , 16.56%. 1.5 Amearance. Color and Odor

2.

Lobeline occurs as needles(from alcohol, ether, benzene (14), it has a bitter taste. Lobeline hydrochloride occurs as rosettes of slender needles (from alcohol (14) or as a white odorless crystalline or granular powder with a bitter taste (15). Lobeline sulfate occurs as hygroscopic crystals (from alcohol (14) or as white crystalline powder, odorless with a bitter taste.


Melting Range

- Lobeline : 130-131' (1,2,14) - Lobeline hydrochloride, the following data have been reported:178-180" (14); not lower than 180' (15); 182' (1,2,11,16); not below 178" (17).

2.2 Eutectic Temperature The eutectic temperature of lobeline hydrochloride is recorded as follows (17): Microscope Hot Stage Benz. Sal. Dic.

135' 146'

-

Hot Bar

-

162" 134'

Benz. = Benzanilide; Sal. = Acetaminosalol; Dic. = Dicyandiamide.


2.3

261

S o l u b i l i t y Data

-

Very s l i g h t l y s o l u b l e i n w a t e r ; s o l u b l e i n h o t a l c o h o l ; i n chloroform; i n e t h e r and i n benzene (Lobeline ( l Y 2 , 1 4 ) . - One gram of l o b e l i n e h y d r o c h l o r i d e d i s s o l v e s i n 40 m l water; 1 2 m l a l c o h o l ; v e r y s o l u b l e i n chloroform and very s l i g h t l y soluble i n e t h e r (14,lS). - One p a r t o f l o b e l i n e s u l f a t e i s s o l u b l e i n about 30 p a r t s o f water; s l i g h t l y s o l u b l e i n a l c o h o l ( 1 4 ) . 2.4

pH Range A 1%s o l u t i o n of l o b e l i n e h y d r o c h l o r i d e i n water h a s a pH of 4.0 t o 6 . 0 ( 1 7 ) .

2.5

Specific Optical Activity The f o l l o w i n g d a t a have been r e p o r t e d : 15

[a]D = -42.85' t o -43' (EtOH) f o r l o b e l i n e ( 1 , 2 y 1 1 y 1 4 ) . 20 [a]D =-43O ( a l c o h o l , C=2) (14) f o r l o b e l i n e HC1 [a]D = - 5 6 t o - 5 8 ' (1% s o l u t i o n ) (17)

1

20 [a]D =-25'

2.6

(C=2) f o r l o b e l i n e s u l f a t e ( 1 4 ) .

Crystal Structure The c r y s t a l s t r u c t u r e o f l o b e l i n e h y d r o c h l o r i d e as C H NO 2 2 27 2' HC1. H 2 0 i s r e p o r t e d ( 1 8 ) . I t was r e c r y s t a l l i z e d from water a s t r a n s p a r e n t n e e d l e s . Lobeline h y d r o c h l o r i d e e x h i b i t e d t h e f o l l o w i n g d a t a : Space group

%(Ao)

&(Ao)

c(Ao)

8.1 14.2 18.0 212121 No. of formula u n i t s / u n i t c e l l = 4 .

D e n s i t y (g.cmj3 observed c a l c u l a t e d 1.24 1.25

The above d a t a were o b t a i n e d from o s c i l l a t i o n and Weissenberg photographs, w h i l e t h e d e n s i t y was d e t e r mined by f l o a t a t i o n . C a l c u l a t i o n of t h e u n i t c e l l c o n t e n t s from t h e c e l l dimensions and t h e observed d e n s i t y r e q u i r e s a m o l e c u l a r of water t o be a s s o c i a t e d w i t h each formula u n i t (18).

FARID J. MUHTADI

268

2.7

X-Ray Powder D i f f r a c t i o n The X-ray d i f f r a c t i o n p a t t e r n of l o b e l i n e hydroc h l o r i d e was determined with a P h i l i p s X-ray d i f f r a c t i o n s p e c t r o g o n i o m e t e r equipped with PW 1730 g e n e r a t o r . R a d i a t i o n was provided by a copper t a r g e t (Cu anode 2000 W, y=1.5480 A'). High i n t e n s i t y X-ray t u b e o p e r a t e d a t 40 KV and 35 MV was used. The monochromator was a curved s i n g l e c r y s t a l (PW 1752). Divergance s l i t and t h e r e c e i v i n g s l i t were 0 and 0.1' r e s p e c t i v e l y . The scanning speed of t h e goniometer used was 0.02 28 p e r second. The X-ray p a t t e r n of l o b e l i n e h y d r o c h l o r i d e is p r e s e n t e d i n F i g . 1. I n t e r p l a n n e r d i s t a n c e and r e l a t i v e i n t e n s i t y are t a b u l a t e d i n t a b l e 1. Table 1 : X-Ray Powder D i f f r a c t i o n P a t t e r n o f L o b e l i n e Hydrochloride

16.54

100.0%

3.40

23.9%

12.01

45.4%

3.35

26.5%

6.67

57.4%

3.30

26.9%

6.51

14.4%

3.24

27.5%

5.99

23.6%

2.99

22.9%

5.39

54.9%

2.75

18.2%

5.25

40.4%

2.39

18.2%

5.06

49.5%

2.32

12.1%

4.61

45.9%

2.03

12.8%

4.40

52.1%

2.00

11.4%

4.23

49.9%

1.99

10.3%

4.02

60.5%

1.82

9.5%

3.71

57.8%

1.61

6.5%

3.65

22.8%

1.49

5.3%

3.52

22.9%

1.43

5.8%

d = i n t e r p l a n n e r d i s t a n c e , 1/10 = r e l a t i v e i n t e n s i t y (based on t h e h i g h e s t i n t e n s i t y of 100).


82

72

62

269

.

52

42

32 28

2'2

i2

Fig. 1 : X-Ray Diffraction Pattern o f Lobeline H C 1 .

i

FARID J. MUHTADI

270

2.8

Spectral Properties 2.8.1

Ultraviolet Spectrum The W absorbance spectrum of lobeline hydrochloride in methanol was scanned from 200 to 400 nm using a Pye-Unicm SP 8-100 Spectrophotometer (Fig. 2). Lobeline hydrochloride exhibited the following absorptivity values (Table 2 ) . Table 2 : UV absorptivity values A(l%, 1 cm)

max nm

log

245

4.08

311

280

3.05

30.3

E

Other reported UV data for lobeline:Solvent Methanol

2.8.2

max nm

Ref. -

0.lNHCl

245(13183) ; 280(1413) 249(A11 = 416)

0.1NH2S04

1 249(A1 = 421)

(11) (19)

Infrared Spectrum The IR spectrum of lobeline hydrochloride as a KBr-pellet (1 : 200 mg) was recorded on a Perkin Elmer 580B Infrared Spectrophotometer (Fig. 3). Assignment of the functional groups have been correlated with the following frequences (Table 3 ) . Table 3 : IR Characteristics of Lobeline Frequency Cm-l 3340 3065-2925 2818

1680

Functional group OH (stretch) CH (stretch)

H~C-NH+

c=o


200

211

30 0

400

nm

F i g . 2 : UV Spectrum of Lobclinc tic1 (In Methanol).

Fig. 3 : IR Spectrum of Lobeline HC1 (KBr-Pellet)


273

Frequency Cm 1600 ,1585 1500 ,1452

-1

F u n c t i o n a l group C=C ( a r o m a t i c s ) C H (bending)

The I R of l o b e l i n e h y d r o c h l o r i d e e x h i b i t e d t h e following o t h e r c h a r a c t e r i s t i c absorption bands:2580, 2510, 1420, 1370, 1350, 1290, 1220, 1205, 1135, 1105, 1080, 1055, 1020, 1005, 995, 970, 945, 920, 875, 820, 795, 765, 695, 670, 645, 690, 582, 525 C m - l . C l a r k e (19) r e p o r t e d t h e f o l l o w i n g p r i n c i p a l peaks f o r l o b e l i n e b a s e i n K B r d i s c : 1687; 1 2 1 1 ; 1115 and 700 C m - l . 2.8.3

Nuclear Magnetic Resonance S p e c t r a 2.8.3.1

‘H-NMR

Spectra

The p r o t o n s p e c t r a o f l o b e l i n e hydroc h l o r i d e were r e c o r d e d , once i n C D C 1 3 on a Varian FT80A (80 MHz) NMR s p e c t r o photometer (Fig. 4 ) , and a n o t h e r i n DMSO-d6 on a Varian XL-200 (200 MHz) NMR spectrophotometer (Fig. 5 ) , u s i n g TMS as an i n t e r n a l reference w i t h b o t h . The p r o t o n chemical s h i f t s are a s s i g ned and p r e s e n t e d i n t a b l e 4.

T a b l e 4 : ’H-NMR C h a r a c t e r i s t i c s of Lobeline. ~~~~

Proton assignment 2 a r o m a t i c H a t C12& C16

Chemical s h i f t s 6 (ppm) 200 MHZ 80 MHZ 8.03-8.09(d)

8 a r o m a t i c H a t C13,14,15

[

‘$2

17.27-7.55 (m)

,Go,&

H

I

t -

Ph

‘N

I

CH3 [91

Ph

Ph

I

CH3 [81

Ph


6.

291

B i o s y n t h e s i s of Lobeline Robinson was t h e f i r s t t o s u g g e s t t h a t l o b e l i n e i n t h e p l a n t LobeZia i n f l a t a i s a r i s e d from l y s i n e and p h e n y l a l a nine ( 3 2 ) . Leete l a t e r proposed t h a t l o b e l i n e i s b u i l t up i n n a t u r e from benzoic a c i d and a c e t a t e o r from a c e t a t e a l o n e ( 3 3 ) . T r a c e r s t u d i e s have demonstrated t h a t l o b e l i n e i s d e r i v e d from p h e n y l a l a n i n e and l y s i n e ( 2 6 , 3 4 ) , t h u s confirming Robinson's s u g g e s t i o n . The s t u d i e s have s p e c i f i c a l l y shown t h a t t h e p i p e r i d i n e n u c l e u s o f l o b e l i n e i s d e r i v e d from l y s i n e and t h e two c 6 - C ~u n i t s a r e d e r i v e d from p h e n y l a l a n i n e ( 2 6 ) . F u r t h e r r a d i o a c t i v e s t u d i e s have e s t a b l i s h e d t h e b i o s y n t h e t i c pathway o f l o b e l i n e i n Lobelia infZata ( 35). T h i s pathway i s presented i n scheme V Phenylalanine [ I ] on deamination with t h e enzyme p h e n y l a l a n i n e ammonia-lyase (which has been i s o l a t ed from plant sources) ( 36 ) y i e l d s t r a n s c i n n a m i c a c i d [11] . Hydroxylat i o n of [ 111 g i v e s 3-hydroxy-3-phenylpropionic a c i d [ 1111. (This has previous Zy been i so l a t e d from LobeZia) ( 37 ) The l a t t e r upon b i o l o g i c a l o x i d a t i o n a f f o r d s b e n z o y l a c e t i c acid [IV] Lysine [V] i s converted e i t h e r v i a 5-aminopentanal [VI] o r v i a pentane-1,s-diamine [ V I I I ] i n t o 2 , 3 , 4 , 5 - t e t r a h y d r o pyridine [VII]. Condensation o f [ I V ] w i t h [VII] y i e l d s t h e amino-ketone [ I X ] which on condensation w i t h a n o t h e r mulecule o f benzoyl a c e t i c a c i d [IV] a f f o r d s n o r l o b e l a n i n e , which upon Nm e t h y l a t i o n y i e l d s l o b e l a n i n e [XI. This i s transformed by p a r t i a l r e d u c t i o n i n t o l o b e l i n e [XI].

.

.

.

I n c o r p o r a t i o n of a number of t h e above i n t e r m e d i a t e s i n t o l o b e l i n e i n l o b e l i a p l a n t s has been demonstrated ( 35 Upon f e e d i n g i n s e p a r a t e experiments each o f (+)- [3-14C] p h e n y l a l a n i n e [ I ] ; [3-14C] cinnamic a c i d [11] ; 3-hydroxy3-phenyl [3-14C] p r o p i o n i c a c i d [111] ; [ Z - l ' k ] l y s i n e [V] and 2 , 3 , 4 , 5 - t e t r a h y d r o [2-14C] - p y r i d i n e [ V I I ] t o s e p a r a t e ZobeZia infZata p l a n t s , r a d i o a c t i v e l o b e l i n e was i s o l a t e d from each experiment. The i n c o r p o r a t i o n of l a b e l l e d l o b e l a n i n e [ X I i n t o l o b e l i n e [ X I ] i n high y i e l d has a l s o been r e p o r t e d ( 38 ) .

3.

FARID J. MUHTADI

292

Scheme V : Biosynthesis of Lobeline HOOC

H2N

n-n-0 NH

CO2H

NH2

CHO

N

0

11x1

[VIII]

# 0 J *

CH I 3

-

Lobeline


7.

293

Pharmacology

T h i s s e c t i o n has been re-written by Dr. Zaki

39 ).

L o b e l i n e mainly s t i m u l a t e s t h e r e s p i r a t o r y ce.-ter by d i r e c t c e n t r a l s t i m u l a t i o n of t h e c e n t e r i n t h e medulla o b l o n g a t a and by r e f l e x l y from t h e chemoreceptors i n t h e c a r o t i d (40,41 ) and a o r t i c b o d i e s (42,43 ) . T h i s a t t h e r a p e u t i c doses of l o b e l i n e leads t o i n c r e a s e i n both t h e r a t e and depth o f r e s p i r a t i o n ( 44 ) . Larger dose may induce cough. Lobeline c a u s e s d i r e c t c e n t r a l s t i m u l a t i o n o f t h e medullary v a g a l c e n t e r , vaso-motor c e n t e r and chemor e c e p t o r t r i g g e r zone (CRTZ) o f t h e vomiting c e n t e r which produces n a u s e a and vomiting. Mild g e n e r a l c e n t r a l s t i m u l a t i o n leads a l s o t o tremors (39,45). L o b e l i n e i s a weak p e r i p h e r a l g a n g l i o n i c s t i m u l a n t . I t produces d i f f e r e n t pharmacological e f f e c t s depending on t h e d o s e and t h e s t a t e o f t h e f u n c t i o n a l a c t i v i t y o f t h e o r g a n s s u p p l i e d by t h e g a n g l i a . These i n c l u d e b o t h s y m p a t h e t i c and p a r a s y m p a t h e t i c e f f e c t s due t o s t i m u l a t i o n o f t h e autonomic g a n g l i a by d e p o l a r i z a t i o n o n l y and when l a r g e d o s e s a r e used ( 4 6 , 4 7 ) . a ) Sympathetic e f f e c t s : are mainly on t h e c a r d i o v a s c u l a r system through s y m p a t h e t i c g a n g l i o n i c s t i m u l a t i o n , i n c r e a s e d catecholamine r e l e a s e (norepinephrine, epinephrine and dopamine) from t h e a d r e n a l medulla and s t i m u l a t i o n o f n o r e p i n e p h r i n e t r a n s m i t t e r release. T h i s l e a d s t o i n c r e a s e c a r d i a c o u t p u t and blood p r e s s u r e (39,43 ) . b) Parasympathetic e f f e c t s : are mainly m a n i f e s t e d on t h e g a s t r o i n t e s t i n a l t r a c t and sweat g l a n d s i n form o f i n c r e a s e d s a l i v a t i o n and m o t i l i t y o f t h e i n t e s t i n e w i t h d i a r r h e a . I t s d i a p h o r e t i c a c t i o n is due t o s t i m u l a t i o n o f t h e sweat gland s e c r e t i o n (48,49 ) . I t h a s been r e p o r t e d t h a t l o b e l i n e a d m i n i s t e r e d t o human s u b j e c t s caused a s l i g h t b u t d e f i n i t e s u p p r e s s i o n o f a p p e t i t e ( a n o r e x i g e n i c a c t i o n ) ( 50 ) . T h i s s u p p r e s s i o n o f a p p e t i t e can a r i s e from a number o f mechanisms known t o be e l i c i t e d by l o b e l i n e ( 51 ) : - Action on t h e c e n t r a l nervous system, p r o b a b l y on t h e a p p e t i t e c e n t e r o r on CRTZ of t h e emetic c e n t e r . - Action on t h e a d r e n a l medulla, c a u s i n g hyperglycemia. - Action on g a s t r o i n t e s t i n a l t r a c t , d i r e c t l y a f f e c t i n g n i c o t i n i c receptors. - Action on pulmonary r e c e p t o r s , c a u s i n g r e f l e x i n h i b i t i o n of i n t e s t i n a l m o t i l i t y (48).

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The most r e c e n t a p p l i c a t i o n o f l o b e l i n e (as t h e hydrochloride or s u l f a t e s a l t taken o r a l l y ) i s t o administ e r it a s a smoking d e t e r r e n t ( t o c o n t r o l symptoms i n p a t i e n t s undergoing withdrawal t r e a t m e n t f o r t h e tobacco h a b i t ) (50,51,52 1. Large t o x i c doses o f l o b e l i n e l e a d s t o b o t h g a n g l i o n i c and neuro-muscular blockade by e x c e s s i v e d e p o l a r i z a t i o n with s e v e r e hypotension, shock, coma and p a r e s i s o r p a r a l y s i s (24,39). Lobelia i s t h e d r i e d aerial p a r t s of LobeZia i n f l a t a L. , i t c o n t a i n s n o t less t h a n 0.25% o f t o t a l a l k a l o i d s , c a l c u l a ted as lobeline (53). Lobelia is s t i l l o f f i c i a l i n s e v e r a l pharmacopoeias, t h e s e i n c l u d e A u s t r i a n , Belgian, B r i t i s h , B r a z i l i a n , Egyptian, French, P o l i s h , Portugese and Spanish pharmacopoeias (24). I t i s used mainly a s Ethereal l o b el i a t i n ct u r e which c o n t a i n s 0.05 t o 0.075% o f a l k a l o i d s c a l c u l a t e d a s lobeline (24).

L o b e l i a i s i n c o r p o r a t e d i n some cough mixtures as s e d a t i v e e x p e c t o r a n t . I t s t h e r a p e u t i c v a l u e i s due t o r e f l e x s t i m u l a t i o n o f t h e b r o n c h i a l s e c r e t i o n modifying i t s p h y s i c a l c h a r a c t e r t o be e a s i l y e x p e l l e d . I t h a s a l s o a c e n t r a l s t i m u l a t i o n effect on t h e cough c e n t e r t h a t f o r c i b l y helps t o c l e a r t h e a i r passages avoiding chest c o m p l i c a t i o n s (39). Storage Lobeline h y d r o c h l o r i d e should be kept i n a t i g h t l y c l o s e d c o n t a i n e r s p r o t e c t e d from l i g h t ( 1 7 ) . Lobeline h y d r o c h l o r i d e i n j e c t i o n s should be kept p r e ferably i n single-dose hermetically-closed containers o r i n m u l t i p l e - d o s e c o n t a i n e r s p r o t e c t e d from l i g h t ( 1 7 ) . S o l u t i o n s f o r i n j e c t i o n s a r e s t e r i l i z e d by f i l t e r a t i o n and s u p p l i e d i n s i n g l e dose a l k a l i - f r e e c o n t a i n e r s , p r o t e c t e d from l i g h t , no b a c t e r i o c i d e should be added (15).


8.

295

Methods o f A n a l y s i s I d e n t if ic a t i o n

8.1

-

The following identification tests have been mentioned under ZobeZine hydrochZoride (17). Warm about 1 m l o f a 1.0% s o l u t i o n w i t h a few d r o p s

of sodium hydroxide TS; t h e a r o m a t i c odor o f a c e t o phenone i s p e r c e p t i b l e . - D i s s o l v e a few mg i n 1 m l o f s u l f u r i c a c i d and add 1 d r o p o f formaldehyde; a r e d c o l o r i s produced ( s e n s i t i v i t y 0 . 1 ug) ( 1 9 ) . - To 1 m l o f 1.0% s o l u t i o n add a d r o p o f ammonia TS; a milky l i q u i d i s o b t a i n e d which c r y s t a l i z e s on s t a n d i n g f o r some time. M e l t i n g - t e m p e r a t u r e of t h e c r y s t a l s , a f t e r washing with a l i t t l e water and d r y i n g , about 120O. - Yields t h e r e a c t i o n s c h a r a c t e r i s t i c of c h l o r i d e s .

The following tests are used f o r the identification of Zobeline and salts:- When drops o f F r o e h d e ' s r e a g e n t a r e added t o few c r y s t a l s o f l o b e l i n e ; a r o s e r e d c o l o r i s produced which changes t o a b l u e c o l o r (25).

are added t o a few c r y s t a l s o f l o b e l i n e ; a f a i n t green c o l o r i s produced which i n t e n s i f i e s on warming. - Ammonium molybdate r e a g e n t g i v e s w i t h l o b e l i n e a g r e y c o l o r which changes t o p u r p l e ( s e n s i t i v i t y 1 . 0 ug) (19). - Ammonium v a n a d a t e s o l u t i o n g i v e s with l o b e l i n e a g r e y c o l o r ( s e n s i t i v i t y 0.5 pg) ( 1 9 ) .

- When d r o p s of Erdmann's r e a g e n t

8.2

M i c r o c r y s t a l Formation

w/v s o l u t i o n of l o b e l i n e HC1 was p r e p a r e d f o r t h e microcrystal tests. 1 t o 2 drops o f t h i s s o l u t i o n was t r e a t e d with e q u a l d r o p s o f t h e s p e c i f i c r e a g e n t on a microscopal g l a s s s l i d e , a f t e r about 5 m i n u t e s , t h e c r y s t a l s s o formed were m i c r o s c o p i c a l l y examined (54). Potassium c y a n i d e r e a g e n t (5%) f u r n i s h e d c l u s t e r s and some i r r i g u i a r r e c t a n g l e s ( p l a t e A ) . Sodium c a r b o n a t e s o l u t i o n (5%) produced c l u s t e r s ( p l a t e B ) , Clarke (19) r e p o r t e d r o s e t t e s w i t h t h i s reagent. Wagner's r e a g e n t gave c l u s t e r s and p r i s m s ( p l a t e C ) . Disodium hydrogen phosphate f u r n i s h e d r o s e t t e s ( p l a t e D). A 0.4%

-

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Mic r oc ry st al s of Lobe1i ne

Plate A

X40

Plate C

Plate D

Plate B


8.3

297

Titrimetric Determinations 8.3.1

Aqueous T i t r a t i o n

Markwell i n 1936 ( 55 ) developed an aqueous t i t r a t i o n method t o determine t h e t o t a l a l ka l oids of l o b e l i a . The method was modified and t h e use of 0.02N s u l f u r i c acid as titrant was recommended (56). The B.P. ( 53 has adopted t h i s modified method f o r the assay of ZobeZia a s follows: The t o t a l l o b e l i a a l k a l o i d s (from log f i n e powder) a r e e x t r a c t e d f i r s t with a mixture of f o u r volumes of e t h e r and one volume o f e t h a n o l (96%) and t h e n a f t e r p u r i f i c a t i o n w i t h chloroform. The chloroform l a y e r i s removed by d i s t i l l a t i o n and t h e r e s u l t i n g r e s i d u e of t o t a l a l k a l o i d s i s d i s s o l v e d i n e t h a n o l (2 ml), 0.01M s u l f u r i c a c i d (10 ml) i s added and t h e e x c e s s of a c i d i s t i t r a t e d w i t h 0.02M sodium hydroxide, u s i n g methyl r e d s o l u t i o n a s an i n d i c a t o r . Each 1 m l o f 0.OlM s u l f u r i c acid i s equivalent t o 0.006749 g of lobeline C22H27N02. Lobelia a l k a l o i d s can a l s o be e s t i m a t e d by a c i d base t i t r a t i o n (57,58). The e x t r a c t e d t o t a l a l k a l o i d s a r e t i t r a t e d w i t h 0.1N HC1 u s i n g methyl r e d a s an i n d i c a t o r . Each 1 rnl of t h e acid = 0.03372 g of

alkaloids calculated as lobeline. Lobeline h y d r o c h l o r i d e can be assayed a f t e r p u r i f i c a t i o n on a chromatographic column (59 ) as f o l l o w s : Lobeline h y d r o c h l o r i d e (0.1 g) i s d i s s o l v e d i n 95% aqueous a c e t o n e (10 ml) and a p p l i e d t o a column of b a s i c alumina (Woelm 5 g ) . E l u t i o n i s c a r r i e d o u t w i t h t h e same s o l v e n t . The e l u a t e i s d i l u t e d w i t h water (25 ml) and t i t r a t e d w i t h 0 . 1 N HC1 u s i n g methylred-methylene b l u e ( 6 : l ) a s an i n d i c a t o r . 8.3.2

Non-aqueous T i t r a t i o n

Lobeline hydrochloride is assayed by t h e nonaqueous t i t r a t i o n method (17 ) : An a c c u r a t e l y weighed q u a n t i t y of t h e s a l t i s d i s s o l v e d i n g l a c i a l a c e t i c a c i d . Acetous mercuric a c e t a t e (10 ml) and dioxan (20 m l )

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a r e added. T i t r a t i o n t o t h e end p o i n t i s c a r r i e d o u t with 0.1N a c e t o u s p e r c h l o r i c a c i d and a f t e r adding 2-3 drops of a c e t o u s crystal violet. Each mZ of 0.1N acetous perchZoric acid is equivaZent t o 0.03739 g of ZobeZine hydro-

chloride, C22H27N02J HCZ.

Good r e s u l t s of e s t i m a t i o n i n t h e non-aqueous media a r e a l s o o b t a i n e d by t r e a t i n g t h e t o t a l a l k a l o i d s with dimethylaminobenzene and t i t r a t i n g w i t h 0.05N p - t o l u e n e s u l f o n i c a c i d ( 60 ) . Lobeline h y d r o c h l o r i d e a s i n j e c t i o n s can b e t i t r a t e d i n non-aqueous media e i t h e r w i t h 0.005 N 4- (benzenesulfonyloxy) benzene s u l f o n i c a c i d o r with 0.01 N 3,4-dichorobenzene s u l f o n i c a c i d u s i n g dimethyl yellow i n both t i t r a t i o n s a s indicator (61). I t has been claimed that these acids gave

b e t t e r r e s u l t s than t i t r a t i o n w i t h toluene-psuZfonic acid (61). The u s e of o t h e r d e r i v a t i v e s o f s u l f o n i c a c i d a s t i t r a n t s f o r l o b e l i n e and o t h e r a l k a l o i d s h a s a l s o been recommended ( 62 ) . These d e r i v a t i v e s i n c l u d e : 6-nitrotoluene-m-sulfonic a c i d ; 4-chloro-2,5-xylenesulfonic a c i d and 3,6dichloro-2,5-xylene s u l f o n i c a c i d . Other non-aqueous t i t r a t i o n have a l s o been reported (63). 8.3.3

Conductimetric T i t r a t i o n s Lobeline h y d r o c h l o r i d e i n i n j e c t i o n s and i n t a b l e t s can be determined e i t h e r by d i r e c t c o n d u c t i m e t r i c t i t r a t i o n with 0.01 N o r 0.005N NaOH i n e t h a n o l medium o r by a d d i t i o n of 0.01N NaOH and e t h a n o l , followed by c o n d u c t i m e t r i c t i t r a t i o n with 0.01 N HC1. The method can be a l s o applied f o r t h e determinations of o t h e r h y d r o c h l o r i d e s of s e v e r a l a l k a l o i d s ( 64 ) .

8.4

Gravimetric Determinations An a s s a y method based on p r e c i p i t a t i o n of l o b e l i a a l k a l o i d s with s i l i c o t u n g s t i c a c i d h a s been developed by Mascre' i n 1930 ( 65 ) . I n t h i s method, t h e t o t a l a l k a l o i d s of l o b e l i a a r e p r e c i p i t a t e d w i t h 5% s i l i c o t u n g s t i c a c i d ( i n t h e c o l d ) . The r e s u l t i n g p r e c i p i -


299

tate is filtered off after 12 hours and incinerated. The weight of the ash multiplied by 0.414 gives the content of alkaloids calculated as lobeline. The above method was further modified to determine the alkaloidal content of galenic preparations of LobeZia infZata after extraction of the alkaloids (66) Barra ( 67 ) used the same method to determine lobeline, but he has simplified the extraction procedure prior to precipitation.

-

A combined precipimetric-titrimetric method was reported to determine the lobelia alkaloids in drugs (68) :Precipitation of lobelia alkaloids with silicotungstic acid was first effected. The silicotungstates so formed were collected, decomposed with ammonia and extracted with ether. The residue after evaporation of ether was dissolved in dilute sulfuric acid and determined titrimetrically. Complex thiocyanate salts as precipitating reagents for determining lobeline have been reported ( 69 ) . The use of tripotassium hexathiocyanate for determining several alkaloids is recommended (69). Other gravimetric determinations were also reported (70,711. 8.5

Polarographic Methods Several alkaloids and salts including lobeline are determined qualitatively and quantitatively by a polarographic method (72). Concentrations of 0.001 to 1% of alkaloids are separated quantitatively on aluminum electrode as anode (wrapped in parchament) and a steel one as cathode. The alkaloids collected at the cathode are washed, dried and their melting points determined for identification. An oscillopolarographic study o f some alkaloids including lobeline has been reported (73) A dropping mercury electrode served as a polarizable electrode and a graphite one served as a reference. All alkaloids gave characteristic cuts in alkaline solutions (0.8 M KOH; 0.5 M LiOH; 5 . 5 M NaOH).

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FARID J. MUHTADI

8.6 Spectrophotometric Methods 8.6.1

C o l o r i m e t r i c Determinations A c o l o r i m e t r i c method f o r t h e determinat i o n o f l o b e l i n e has been r e p o r t e d . This method depends on d e g r a d a t i o n of l o b e l i n e i n t o a c e t o phenone and measuring t h e l a t t e r ( 74 ) . Acetophenone d e r i v e d from l o b e l i n e i s mixed with t h e r e a g e n t 0.1% 2,4-dinitrophenylhydrazine i n 2 N H C 1 ( 5 ml). After s t a n d i n g f o r 2 hours, t h e mixture i s shaken with carbon t e t r a c h l o r i d e (10 ml) Upon s e p a r a t i o n , t h e e x t r a c t i s washed with water, d r i e d with anhydrous sodium s u l f a t e and t h e c l e a r s u p e r n a t a n t l i q u i d i s measured a g a i n s t a blank a t 370 nm.

.

A combined paper chromatographic-colorimetric d e t e r m i n a t i o n o f l o b e l i n e has been recommended ( 75 ) and t h i s i s a s f o l l o w s :

heparation of chromatograms Paper s h e e t s are impregnated with a mixture s o l u t i o n c o n t a i n i n g formamide (9 ml), ammonium fvrmate (0.8 g ) , formic a c i d ( 1 ml) and absol u t e methanol (20 ml). The p a p e r s are d r i e d a t room temperature f o r 50 minutes. Separation of lobeline Spots of l o b e l i n e s o l u t i o n o r l o b e l i a a l k a l o i d s i n chloroform are a p p l i e d on t h e s t a r t i n g l i n e s of t h e above chromatograms and t h e s e a r e developed with t h e s o l v e n t chloroform-benzene ( 9 : l ) s a t u r a t e d w i t h formamide. After developement t h e chromatograms are d r i e d . CoZorimetric determination The s p o t s corresponding t o l o b e l i n e are c u t o u t and shaken f o r 3 minutes i n a s t o p p e r t u b e w i t h 2 m l of b u f f e r e d t r o p a e o l i n 00 s o l u t i o n (pH 3 . 4 ) and 5 m l chloroform. The r e s u l t i n g mixture i s c e n t r i f u g e d f o r 2 minutes. An a l i q u o t o f t h e chloroform l a y e r i s measured u s i n g a s u i t a b l e f i l t e r photometer. A blank i s t r e a t e d s i m i l a r l y and t h e l o b e l i n e c o n t e n t i s t h e n read from a c a l i b e r a t i o n curve. The mean e r r o r i s 2 2 .O% (75).


30 1

F u r t h e r two c o l o r i m e t r i c methods have been d e s c r i b e d f o r t h e d e t e r m i n a t i o n of l o b e l i n e and t h e o t h e r a l k a l o i d s of l o b e l i a . These methods depend on formation of a dye complex w i t h a l k a l o i d s and measuring t h i s complex a t c e r t a i n wavel e n g t h s (76,77). In t h e f i r s t method ( 7 6 ) , l o b e l i n e ( ~ 0 . 5mg) i s e x t r a c t e d from paper chromatography (which used f o r i t s s e p a r a t i o n ) with c i t r a t e - p h o s p h a t e b u f f e r o f pH 7.5 (20 m l ) , 0.15% Bromothymol b l u e s o l u t i o n ( 1 ml) i s added and t h e m i x t u r e is t h e n e x t r a c t e d with chloroform (3x20 ml). The combined chloroform e x t r a c t s are mixed w i t h 2% e t h a n o l i c b o r i c a c i d (25 ml). The r e s u l t i n g m i x t u r e i s f i l t e r e d , d i l u t e d t o 100 m l w i t h e t h a n o l and i t s e x t i n c t i o n i s measured at 436 run a g a i n s t a r e a g e n t blank i n 2-cm. c e l l . The r e p r o d u c i b i l i t y t 2% ( 76 ) . In t h e o t h e r method, l o b e l i n e and t h e t o t a l a l k a l o i d s of l o b e l i a and i t s p r e p a r a t i o n s can be determined by almost s i m i l a r t e c h n i q u e (77). The powdered drug i s e x t r a c t e d by s h a k i n g w i t h a mixture of methanol - 0.1 N H C l ( 1 : l ) and centrifuging. An a l i q u o t of t h e s u p e r n a t a n t l i q u i d ( n e u t r a l i zed w i t h NaOH s o l u t i o n ) o r of l o b e l i n e i n j e c t i o n i s mixed w i t h 0.01% methyl orange i n McI l v a i n e b u f f e r s o l u t i o n (pH 5.0) and t h e r e s u l t i n g dye complex-alkaloids a r e e x t r a c t e d i n chloroform. The chloroform e x t r a c t i s shaken with 0.1 N HC1 c o n t a i n i n g 5 % N a C l and t h e a b s o r bance o f t h e l i b e r a t e d dye i n t h e a c i d s o l u t i o n i s measured at 510 nm. Lobeline remains i n t h e chloroform l a y e r ( a s i t s HC1 s a l t ) and t h i s l a y e r is t r e a t e d w i t h more dye s o l u t i o n t h e n t h e m i x t u r e i s e x t r a c t e d with 0 . 1 N HC1 and t h i s a c i d e x t r a c t c o n t a i n s dye e q u i v a l e n t t o t h e l o b e l i n e . The e x t i n c t i o n o f t h i s i s a l s o measured a t t h e same wavelength. B e e r ' s law i s obeyed f o r 0.04 t o 0.7 mg o f l o b e l i n e . The c o e f f i c i e n t of v a r i a t i o n o f t h e method i s 1.24% ( 7 7 ) . Other c o l o r i m e t r i c method f o r l o b e l i n e d e t e r m i n a t i o n h a s been r e p o r t e d ( 7 8 ) .

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8.6.2

-

8.6.3

UV Determinations Lobeline was determined i n ampoules, e t h e r e a l l o b e l i a t i n c t u r e and powder l o b e l i a by c h a r g e - t r a n s f e r complexation t e c h n i q u e ( 7 9 ) . S e p a r a t e p o r t i o n s o f l o b e l i n e e x t r a c t s were t r a n s f e r r e d i n t o two f l a s k s (A 6 B), 5 m Mi o d i n e (2 ml) was added t o f l a s k A and t h e c o n t e n t s of b o t h flasks were made up t o 20 m l with chloroform. The absorbance o f t h e s o l u t i o n i n f l a s k A was measured first a t 292 run a g a i n s t a blank o f 0.4 m M-iodine i n chloroform and a g a i n a t 292 nm a g a i n s t t h e s o l u t i o n i n f l a s k B t o o b t a i n a d i f f e r e n c e reading. Beer's law was obeyed f o r 1.6 t o 9.6 mgl-' ( 7 9 ) . Lobeline h y d r o c h l o r i d e i n j e c t i o n s are assayed by a UV t e c h n i q u e ( 1 7 ) : An a c c u r a t e l y measured volume ( e q u i v a l e n t t o about 0.002 g o f l o b e l i n e HC1) i s d i l u t e d w i t h a b u f f e r s o l u t i o n (prepared by d i s s o l v i n g 3.4g of sodium a c e t a t e i n 5 m l a c e t i c a c i d and s u f f i c i e n t w a t e r t o produce 250 m l , pH 4.7) t o produce 100 m l . The absorbance o f an a l i q u o t o f t h i s i s determined a t 248 nrn and t h e c o n t e n t o f l o b e l i n e HC1 i s t h e n c a l c u l a t e d u s i n g lobel i n e H C 1 as a s t a n d a r d r e f e r e n c e . T u r b i d i m e t r i c Determinations Lobeline i n b i o l o g i c a l f l u i d s (urine and bZood serum) has been determined by a s p e c t r o p h o t o m e t r i c method (80). The method i s a s f o l l o w s : To a u r i n e sample (10 ml), mercuric c h l o r i d e (0.1 g) and 2 M NaOH ( 1 ml) are added. The mixture is t h e n f i l t e r e d through a f i l t e r p a p e r 10% HC1 i n anhydrous a c e t i c a c i d (2 ml) i s added t o t h e f i l t r a t e , and t h e mixture i s t h o r o ughly mixed. To an a l i q u o t o f t h e mixture (5 ml), Nessler r e a g e n t (0.2 ml) i s added and a f t e r 20 minutes, t h e t u r b i d i t y s o produced is measured a t 580 nm a g a i n s t a blank. Beer's law i s obeyed with 2 t o 20 ug o f lobeline per m l biological fluid. The mean e r r o r o f t h e procedure is 2 1 . 2 % (80)

-


8.7

303

Chromatographic Methods 8.7.1

Paper Chromatography

Clarke ( 19 1 described the following technique f o r the i d e n t i f i c a t i o n of lobeline. This technique was originally deviced t o screen n i t r o genous bases (81,82). Whatman No.1 s h e e t s 14x6 i n c h e s , were b u f f e r e d by d i p p i n g i n 5% s o l u t i o n o f sodium dihydrogen c i t r a t e , b l o t t i n g and d r y i n g a t 25' f o r 1 hour, i t can be s t o r e d i n d e f i n i t e l y . A s o l v e n t composed o f 4.8 g c i t r i c a c i d i n a mixture o f 130 m l w a t e r and 870 m l n-butanol was employed. Lobeline e x h i b i t e d Rf v a l u e o f 0.82. Lobeline was v i s u a l i z e d w i t h one o f t h e followings : - Examination under UV (254 nm), g i v e s s t r o n g absorption. - Spraying with i o d o p l a t i n a t e r e a g e n t . - Spraying with D r a g e n d o r f f ' s r e a g e n t . A s o l v e n t system c o n s i s t i n g o f chloroform/ benzene ( 9 : l ) was used t o s e p a r a t e and i d e n t i f y l o b e l i a a l k a l o i d s on paper chromatography. Lobeline e x h i b i t e d Rf v a l u e o f 0.78 i n t h i s system (83).

Other systems f o r p a p e r chromatography have a l s o been r e p o r t e d (75,841. Quantitative determination of lobeline h y d r o c h l o r i d e ( a s 0.2 mg i n j e c t i o n s ) was p e r formed on paper chromatography ( 85 ) . Lobel i n e was produced as s p o t s on 0 . 3 C a t i o n i t e paper and a f t e r developement, s p o t were measured by a p l a n i m e t e r . A s t a n d a r d e r r o r o f 2 2.06 was r e p o r t e d . 8.7.2

Thin Layer Chromatography (TLC)

Many TLC techniques were reported f o r the f a s t and reZiabZe i d e n t i f i c a t i o n of ZobeZine and other lobelia alkaloids. Several of these are presented in the following table 7 .

304

FARID J. MUHTADI

Table 7 : Thin Layer Chromatography of Lobeline Chromatogram 1.. Silica gel G

mm layers) 2. Silica gel G layers dipped in or sprayed with 0.1 M potassium hydroxide in methanol and dried 3. Silica gel G layers I1 4. (0.25

So 1vent

System

Methanol-strong ammonia (100:1.5) Methano1-strong ammonia solution (1OO:l.S) Cycloh.exane-toluenediethylamine (75 :15 :10) Chloroform-methanol

Rf 0.55

0.61 0.171

(90: 10)

0.35

Chloroform-acetonediethylamine (5 :4: 1) Chloroform-diethy lamine

0.68

(9:l)

0.90

Cyclohexane-chloroformdiethylamine (5 :4 :1) 6. 11 Cyclohexane-diethylamine (9 : 1) II 7. Benzene-ethylacetatediethylamine (7 :2 :1) 8. Basic silica gel Methano 1 9. Aluminum oxide Chloroform layers II 10. Cyclohexane-chloroform (7:3) - 0.05% diethylaminc ( 3 drops/100 ml) 11. Kieselgel (silica Methano 1- 2 5 % ammonia (100 :1.5) gel) F254

0.48

5.

It

Other TLC have also been reported (90,91).

0.63

0.14 0.48

0.55 0.55

0.60 1.25

relative to bupranolol

305


8.7.3

Gas Liquid Chromatography (GLC)

Few GLC systems have been described t o i d e n t i f y and determine lobeline. The folzowing are these systems: System I ( 22,921 Column Condition :

2 . 5 % SE-30 on 80-100 mesh Chromosorb G ( a c i d washed and d i m e t h y l d i c h l o r o s i l a n e t r e a t e d ) 2m x 4mm i n t e r n a l diameter g l a s s column. Column t e m p e r a t u r e 100-300°.

C a r r i e r Gas: Reference :

Nitrogen a t 54 ml/minute n-Alkanes w i t h an even number of carbon atoms. R I (Retention Index) f o r l o b e l i n e 1780.

Identification: System I1 ( 89 ) Column C o n d i t i o n :

Glass column 6 f t . x 2 mm i n t e r n a l d i a m e t e r . Packed w i t h 3% OV-1 on Chromosorb W-HP 100-120 mesh. Column temperature 150-250°, programmed a t 10°c/minute.

C a r r i e r Gas:

Nitrogen a t 50 ml/minute; a i r 120 ml/minute; hydrogen 2 ml/minute.

Detector:

N-FID.

Reference:

2 -amino- 5 - c h l oroben zophenone

Identification:

Rel. t R ( r e l a t i v e r e t e n t i o n time) f o r l o b e l i n e 0.71. R I 1823.

.

System I11 ( 8 9 ) Column Condition:

Glass column 6 f t . x 2mm i n t e r n a l diameter. Packed w i t h OV-17 on Chromosorb W-HP, 100-120 mesh. Column t e m p e r a t u r e 15O-25O0c, programmed a t 10°c/minute.

C a r r i e r Gas:

Nitrogen a t 50 ml/minute; a i r 120 ml/minute; hydrogen 2 ml/minute.

306

FARID J . MUHTADl

8.7.4

Detector:

N-FID.

Reference:

Methagualone.

Identification:

Rel. t R ( R e l a t i v e r e t e n t i o n time) f o r l o b e l i n e 0.6. RI 2078.

High Performance Liquid Chromatography (HPLC)

For the separation, identification as well as quuntitation of lobeline, few HPLC systems were reported and these are as follows:

System 1 : The f o l l o w i n g system 1 h a s been employed t o i d e n t i f y and q u a n t i t a t i v e l y determine l o b e l i n e hydroc h l o r i d e i n antismoking chewing gum ( 93 ) . The method depends on degrading l o b e l i n e i n t o a c e t o phenone and determine t h e l a t t e r . Procedure: To chewing gum (1 g) , aqueous 95% e t h a n o l (20 ml), 1 M KOH (10 ml) and water (10 ml) a r e added. The r e s u l t i n g m i x t u r e i s h e a t e d under r e f l u x f o r 4 hours and i s t h e n d i s t i l l e d a f t e r adding w a t e r (100 ml). The d i s t i l l a t e i s d i l u t e d t o 100 m l with water. An a l i q u o t o f 10 p1 of t h i s i s analyzed by t h e following HPLC system. Column:

S p h e r i s o r b ODS (10 pm).

Mobile phase :

Methanol-water ( 1 : 2 ) .

D e t e c t i o n : UV a t 249 nm.

The caliberation graph was rectiZinear for 0.03 to 0.09% of Zobeline in the sample. System 2 : T h i s system i s used t o i d e n t i f y l o b e l i n e (89). Apparatus: A Perkin Elmer LC-series 312. 10 pm, 250x4 mmz.

Column:

RP-18,

Mobile phase :

A c e t o n i t r i l e (Lichrosolv), flow r a t e 1 ml/minute.

Reference: MPH = 5-(p-methylphenyl)-5pheny 1hydrant o i n .


Detection:

307

UV a t 220 nm. Rel. t R 0.73

System 3 : T h i s system i s a l s o employed f o r t h e i d e n t i f i c a t i o n of l o b e l i n e (89)

-

Apparatus :

A Perkin E l m e r LC-series 3 1 2 .

Column :

RP-18, 10 pm, 250 x 4 mm2

Mobile phase :

156 g a c e t o n i t r i l e + 344 g phosphate b u f f e r (4.8 g 85% H3P04 and 6.66 g KH2P04) pH 2 . 3 .

flow r a t e 1 ml/minute ( i s o c r a t i cally).

8.7.5

Detection:

UV a t 220 nm

Reference:

MPH Rel. t R 0.77

.

Ion Exchange Resins

This technique is used for separation and purification of organic substances as we22 as for quantitative determinations of these substances. - An i o n exchange method was used f o r t h e q u a n t i t a t i v e a n a l y s e s o f several a l k a l o i d s

.

including lobeline ( 9 4 ) The s o l u t i o n o f l o b e l i n e h y d r o c h l o r i d e passed through a column (14 cm x 1 cm) packed with Wofatit KPS (Zn 2 + form). The Zn2+ i n t h e e l u a t e was determined with 5mM EDTA i n t h e p r e s e n c e of Eriochrome b l a c k T i n an ammonia b u f f e r medium o f PH 10.4. - A l g i n i c a c i d a f t e r t r e a t m e n t with formaldehyde was used a s c a r b o x y l i c c a t i o n exchange medium. The a b s o r p t i o n from aqueous s o l u t i o n s and subsequent e l u t i o n with ammonium s u l f a t e s o l u t i o n followed by s p e c t r o p h o t o m e t r i c d e t e r m i n a t i o n o f s e v e r a l a l k a l o i d s i n c l u d i n g l o b e l i n e were performed ( 9 5 ) .

308

FARID J. MUHTADI

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61

94. J. J a r z e b i n s k i , Acta Pol. Pharm., 33 493 (1976); Anal. Abst., 33, 2E10 (1977). 95. J . S . F a s t e r and J.W. Murfin, A n a l y s t ,

86, 32

(1961).

ACKNOWLEDGEMENT

The a u t h o r would l i k e t o thank M r . Uday C. Shanna, Dept. o f Pharmacognosy, College o f Pharmacy, Riyadh, Saudi Arabia f o r h i s v a l u a b l e and s i n c e r e e f f o r t s i n t y p i n g t h i s manuscript.

ANALYTICAL PROFILE OF LOMUSTINE

FAHAD JABER AL-SHAMMARY

Clinical Laboratories Department, College of Applied Medical Sciences, King Saud University, P.O. Box 10219, Riyadh-11433, Saudi Arabia.


315

Copyright 0 1990 by Academic Press. Inc. All rights of reproduction in any form reselved


316

Content I.

Description

1.1 1.2

1.3 1.4 1.5

2.

Nomenclature 1.1.1 Chemical Names 1.1.2 Generic Names Formulae 1.2.1 Empirical 1.2.2 Structural 1.2.3 CAS Registry Number Molecular Weight Elemental Composition Appearance and color

Physical Properties 2.1 Melting Range 2.2 Solubility 2.3 Stability 2.4 X-Ray Powder Diffraction 2.5 Spectral Properties 2.5.1 Ultraviolet spectrum 2.5.2 Infrared spectrum 2.5.3 Nuclear Magnetic Resonance Spectrum 2.5.3.1 Proton spectrum (PMR) 2.5.3.2 Carbonis NMR 2.5.4 Mass spectrum

-

3.

Synthesis

4.

Metabolism and Mechanism

5.

Uses

6.

Cautions and Adverse effects

7.

Methods of Analysis 7.1 7.2

Elemental Analysis Identification

3 17

MMUSTINE

7.3 7.4 7.5

7.6

Spectrophotometric Polarographic Chromatographic 7 . 5 . 2 Gas Chromatography 7.5.2 Thin layer chromatography 7.5.3 High performance liquid chromatography Thermal Analysis

8.

Acknowledgements

9.

References


318

I..

DescriDtioJ

1.1

Nomenclature 1.1.1

Chemical Names

l-(2-chloroethyl)-3-cyclohexyl)-l-nitrosourea (1,2,3,4,5)* (a)

(b) N-(2-chloroethyl)-N/ -Cyclohexyl-N-nitrosourea (1,4)* @

Urea N-(2-chloroethyl)-N -cyclohexyl-N-nitrosourea (5). (c)

1.1.2

Generic Names

CCNU(l,S),NSC 79037(1,4).RB 1509(1,4),Belustine(l). CeeNU(1,5). Lucostine (2). Lomustine. 2.2

Formulae 1.2.1

Emirical

CsHi sClN302 1.2.2

Structural

No, CI

-CH~CH,/

1.2.3

0

II

N-C-NH

CAS Rejzistrv Number

13010-47-4 (4).

319

LOMUSTINE

1.3

Molecular Weight 233.69

1.4 C. N. 1.5 A

2.

Element Cornweition 46.25% 17.98%

H. 0.

6.90% 13.69%

CI.

15.18%

Amearance and Color

yellow crystalline powder (1,2,3,4,5).


Melting Range

About 89°C (2,4). 90°C ( 1 ) . 2.2

Solubilitx

Practically insoluble in water(2,3,5) very slightly soluble in water (1 mg/20 ml) (4) freely soluble in chloroform and soluble in ethanol and acetone(3,4) and highly soluble in lipid (5,6), also soluble in saline (7,8)* 2.3

Stability

Drug solutions are stable for 7 days at 0°C ( 2 ) . Commercially available lomustine capsules should be stored in well closed containers at a temperature less than 40'C preferably between 15-30'C. Lomustine capsules are stable for at least 2 years when stored in well closed containers at room temperature(b).The bulk drug should be stored in a deep freeze and protected from moisture(1). 2.4

X-Ray Powder Diffraction

The X-Ray diffraction pattern of Lomustine was determined on a Philips X-Ray diffraction spectrogoniometer equipped with PW-1730/10 generator (8). Radiation was provided by a copper target (cu anode 2000W,y = 1.5418A) and high intensity X-ray tube operated at 40 KV and 35MA. Divergence slit and he


320

Table 1:

5.371 7.346 8.222 11.550

X-ray diffraction pattern of loauatine

16.6068 12.0342 10.7534 7.6617

13.088 16.244

6.7645 5.4566

1.513 17.480 18.342 19.296

5 3682 5.0734 I

2 1 582 22.154

4.8368 4 6 5998 4.1174 4.0123

22.416 23.187

3.9662 3.8359

I

4 6125

1.611 100 0.552 0.523 1.695

1.010 0,692 2.349 4.062

24 I 056

3.6993

0.433

3.6659 3.5789 3.5158

0.554 4.814 1.644

26.164 26.540

3.4058 3.3585

27.263 28.135

3.2710 3.1716

29,054 29.677

3.0733

30.441

2.9364 2.9006 2.7764 2,7488

30.825 32.241 32.574 33 368 34.394

2.2208 2.2049 2.1578

0.607 0.511 0 690

42.092 42.921

2 1467

1.894

2.1071

0.802

I

I

16.60 0 501 6.071 0.370

24.279 24.878 25.332

3.0102

40.623 40.929 41.865

4 I848

0.558 0.163 0.342 1.468 0.886 0,334 0 307 I

2.6852 2.6074

0.486 0.346 0,256 0.550

34,672 36.123 36,945

2.5871 2.4864 2.4330

0 287 0.380 0.435

37.216 37,918 38.413

2.4159 2.3728 2 * 3434

0.621 1.870 0.380

40.039

2.2519

0.374

I

a

=

1/10 =

Interplanner distance. Relative intensity based on the highest as 100.

321

LOMUSTINE

receiving slit were 1 and 0.1 respectively. The unit was equipped with Philips PM 8210 printing recorder and digital printer. The x-ray pattern of lomustine is presented in fig. (1). Interpplanner distance and relative intensity are listed in table (1). 2.5

Smctral Pro~erties 2.5.1


The UV spectrum of Lomustine in ethanol was scanned from 200 to 3 5 0 n m using 4054 UV/VIS L K B spectrophotometer (8). It exhibited a maximum at 230 nm (Fig 2). 2.5.2

Infrared Spectruu

The infrared spectrum of Lomustine as KBr disc i s presented in (Fig. 3) and is recorded on Perkin-Elmer infrared spectrometer model 5808. Frequency assignments for some of the characteristic bands are listed in table (2). Table 2: Infrared Spectral Assignments for Lomustine. Freauencv (cm-1 1

Assignment

3360

N-H stretch

2850-2960

CHz = CHz

1703

C=O stretch

1534 1491 1083

Characteristic vibrations of the cyclohexyl ring N-O-N linkage.

322


4

I

I

I

I

I

I

I

I

2

Fig. 1 The x-ray diffraction pattern of Lomustine.

I

0

323

LOMUSTINE

0.

nm

.

Fig 2. UV Spectrum of Lomustine in Ethanol.

0

* 0 0 W

0

0

aD

0 0

0 0 0

2 0 0

z m a W o m

zO Is

;: -3 0 0 0 N

0

0 4

N

0 D

m

N

0 0

m N 0

0

m Y)

3

325

LOMUSTINE

2.5.3

Nuclear Mametic Resonance SDectrur 2.5.3.1

Proton SDectrur (Pmal

The PMR spectrum of lomustine in DMSO-ds presented in Fig (4), was recorded on a varian XL-200 NMR spectrometer using TMS as an internal reference. The structural assignments have been listed in table ( 3 ) . Table ( 3 )

PMR characteristics of Lomustine

Group

Chemical shift (porn)

-

CHZ

1.28 m

-

CHz (cyclohexyl)

3.47 t

-

C-H

3.49

m

N-CH2

4.15

t

-CHZ

7.27

s

S= singlet, t= triplet, m= multiplet. 2.5.3.2

13C-NMR Spectra

The 13C-NMR spectrum of lomustine in DMSO-ds using TMS as an internal reference is recorded on a Joel FX 100 FT NMR spectrometer ( 8 ) and is presented in Fig. ( 5 ) . 2.5.4

Mass SDectrur

The mass spectrum of lomustine is presented in Fig. (6). This was obtained by electon impact ionization on a Finnigen 300 mass spectrometer by direct inlet probe at 270'C. The electron energy was 70 eV. The most prominent fragments their relative intensities and some proposed ion fragments are given in table (4)

m

326

. c N

aJ

I

Fig. 5:

13C-NMR noise decoupled spectrum of Lomustine.

H

bp

"I L

Cu

0 N

329

LOMUSTINE

Table 4 :

m/e

Mass Fragments of Lomustine

Relative intensity%

Ions

233

2

126

56

108

8

83

100

55

59

+

41

36

N-CH2 -CH+

3.

(Lomustine)

Mi

t N

\ CHZ-CHZ-C1

CH-CH2-N-N

Synthesis ( 9 ) A practical and convenient method for synthesizing

antitumor compound (Lomustine) is based on the reaction of 2-chloroethyl isocyanate with 2 , 4 , 5 , trichlorophenol to produce 2 , 4 , 5 , trichloropheny1-N(2-chloroethy1)carbamate which on nitrosation with nitrosyl chloride in pyridine yeilds 2 , 4 , 5 trichlorophenyl-N-(2-chloroethyl) N-nitrosocarbamate as intermediate followed by the formation of N-(2chloroethy1)-N-cyclohexyl-N-nitrosourea (lomustine), The product is isolated as crystalline, stable compound in very good yeilds.


330

Scheme:

ClCHCH,-NC=O

+HO

2

2-Chloroethyi isocyanate

CI 2,4,5 trichloro phenol

Cl 2,4,5 trichloro phenyl 2 (N-Chloroethyl) carbamate

CI CH

2

NO

Cl 2,4,5 trichloro phenyl

I N-(2-chloroethyl)N-nitrosocarbamate. NO ClCH CH N 2

2

-c

II

NH

0 N-(2-chloroethyl)

N-cyclohexyl-N-nitrosourea.

(Lomust ine)

LOMUSTINE

4.

331

Metabolism and Mechanism Lomustine is absorbed (2) from the gastro-intestinal tract and is rapidly metabolised; metabolites have a prolonged plasma half life reported to range from 16-48 hours. The active metabolites readily appear in the crebrospinal fluid. About half a dose is excreted as metabolites in the urine within 24 hours but less than 75% is excreted within 4 days. About 60% of the cyclohexyl moiety of lomustine is reported to be bound to plasma proteins. Lomustine and its metabolites (6) cross the blood brain barrier and are rapidly transported into cells due to their high lipid solubility. Drug is not detectable in CSF but active metabolites appear in substantial concentrations within 30 minutes after oral administration of lomustine CFS concentrations of metabolites have ben reported to be 15-50% or greater than concurrent plasma concentrations. Lomustine metabolites are present in milk, but in concentrations less than those in maternal plasma. Lomustine is metabolized (6) in one hour after oral administration. The half life of lomustine metabolites is biphasic; although the initial plasma half life is 6 hours. The second phase plasma half life is 1-2 days and 15-20% of the metabolites remain in the body 5 days after administration of lomustine. Prolongation of plasma concentration is thought to reflect a combination of protein binding and enterohepatic circulation of metabolites. It is distributed among the tissues with a volume of distribution greater than total body water. In the cerebrospinal fluid, the concentration of metabolites reaches 150% of that in plasma. Biotransformation occurs throughout the body, the half life is less than 1 hour. Lomustine probably acts by a dual mechanism the cytotoxic effect involves the inhibition of DNA and RNA synthesis through alkylation and interference with histidine utilization, thereby upsetting the 1-carbon metabolic transfer process.


332

5.

m. Lomustine has been used ( 2 ) in the treatment of brain tumors, Hodgkin's disease, and also lung cancer, malignant melanoma and various solid tumors. Clinical studies ( 6 ) of lomustine alone in the treatment of bronchogenic carcinoma, non-Hodgin's lymphomas, malignant melanoma, breast carcinoma, renal cell carcinoma, and carcinoma of the GI tract, Lomustine has been used topically in the treatment of psoriasis and mycosis fungoides. Lomustine is given (10) by mouth to adults and children as a single dose of 130 mg per m 2 body surface, should be given to patients with compromised bone marrow function. Doses are also generally reduced when lomustine is given as a part of combination regimen. Providing blood counts have returned to acceptable levels, that is, platelets have 100,000 per mm3 and leucocytes above 4000 per m m 3 , doses may be repeated every 6 weeks, and should be adjusted according to the haemotological response.

6.

Cautions and Adverse Effects Lomustine is highly ( 6 ) toxic drug with a low therapeutic index. Nausea and vomiting occur in 45-100% of patients within 1-6 hours, after ingestion of an oral dose of lomustine. Thrombocytopenia and leukopenia reach ( 5 ) nadirs in 4 and 6 weeks respectively and last 1-2 weeks. Stomatitis, alopecia, anemia, and mild transient hepatotoxicity occasionally occur. Dysarthria, ataxia, lethargy and disorientation have been reported. Monitoring of leukocyte counts is required. When other myelosuppressive drugs are in use or have been used within the prior 4 weeks, the dose of lomustine should be reduced. Other less frequently ( 6 ) reported adverse effects of lomustine include hepatotoxicity manifested by transient elevation of liver function test results and alopecia. A decrease in kidney size, progressive azotemia, and renal failure have occured in patients who received large cumulative dose after prolonged

LOMUSTINE

333

therapy with lomustine and related nitrosoureas, renal damage has also occured occasionally in patients receiving lower total doses. A few cases of pulmonary infitrates and fibrosis, with onset occuring 6 months or longer after initiation of lomustine therapy and and cumulative doses of 600-1040mg have been reported-neurologic reactions including disorientation, lethargy, ataxia and dysarthria have been reported in some patients receiving lomustine. Adverse dermatologic effects resulting from topical application of lomustine for the treatment of psoriasis and mycosis fungoides including contact dermatitis, short term hyperpigmentation, long term telangiectasia, cutaneous pain, pruritus, and a Nikolsky-like epidermal separation in inflamed uninvolved skin. Adverse systemic myelosuppressive effects have also been reported following topical use of the drug. Methods of Analysis

7.

7.1

C

N

7.2

Elemental Analysis 46.25% 17.98%

H

0

6.90% 13.69%

C1

15.18%

Identification

a) The infrared absorbtion spectrum, is concordant with the reference spectrum of lomustine (3). b) Carry out the test in subdued light and prepare the solution immediately before use. The light absorbtion, in the range 200 to 350 nm of 0.002% w/v solution in ethanol (96%) exhibits a maximum of 230nm. The absorbance at 230nm is about 0.52 (3) c) To 0.2 g add 20 ml of a 20% w/v solution of potassium hydroxide and boil under a reflex condenser, for 2 hours. Add 75 ml of water and 4 ml of nitric acid, cool and titrate with 0.05M silver nitrate vs determining the end point potentiometrically. Repeat the operation without the substance being examined. The difference between the titrations represents the amount of silver nitrate required. Each ml of 005M


334

silver nitrate vs is equivalent to 0.01168g of C9H16C1N302 ( 3 ) . 7.3

SpectroDhotometric Wethod

For the analysis (11) of lomustine encapsulated in liposomes, after isolation of the drug containing liposomes from free drug, a portion of liposomes was mixed with an equal amount of conc HC1 and heated at 1000 until the dispersion was optically clear. The liquid was evaporated, and the residue was taken up in 2ml of acetate buffer solution (PH 4.62) and treated with 0.2-0.5 m1 of a 0.5% s o l u t i o n o f 4-(4-nitrobenzyl) pyridine in acetone. The mixture, in a sealed container, was heated in boiling water for 15-30 minutes and then cooled in ice. After diluting the filtrate to 5101 with acetone (avoiding exposure to light), 0.5ml of O.5M-NaoH was added and 1 minhtes later, the absorbance was measured at 450nm to determine the alkylating activity. 7.4

PolaroRraDhic Method

The method (12) involves the acid hydrolysis of lomustine which liberates HN02, an azo-dye is formed when a solution containing 0.01 to 0.04% of lomustine, 0.09% of sulphanilic acid 0.03% of N-l-napthylethylenediamine dihydrochloride in aqueous 40% dimethylformamide is heated for 5 minutes on a boiling water bath. The mixture is then cooled and absorbance is measured at 562 nm. The limit of detection is 0.4 to 06 pg/ml. A solution of 0.05M H2S04 is optimum for the pulse polarographic determination of lomustine; The limit the E valve is -0.475 V (vs. the s.c.e.). of determination is 5 ng/ml. 7.5

ChromatoaraDhic Methods 7.5.1 Gaa ChromatonraDhy

Different methods of Gas chromatography have been used for the determination of lomustine are summarised in the table ( 5 ) .

Table 5:

Summary of conditions used for GC lomustine

Column support

Mesh

Temperature

Low rate

Sample

Ref.

Glass column (1.5 m X 2 mm) packed with 3%

100-120

--

40 ml/min helium carrier gas.

Plasma

13

(1.2 m X 2 mm) 10% of SE-30 on Gas-Chrom Q.

100-120

150"

Plasma

14

ov-1.

(1.2 m X 2 mm) packed with ultrabond 20 M

Nz gas

Plasma or urine

15

25-M fusedsilica, SE 30 capi 11ary column.

--

Plasma

16

carrier gas

FAHAD JABER A L - S H A M M Y

336

7.5.2 Thin Layer ChroBatoflraDk (TLC)

The separation of drug is carried out by TLC (3) using Merck silica gel and a mixture of toluene and glacial acetic acid (80.20) as the mobile phase. Apply seperately to the plate 4 yl of each of three freshly prepared solutions of the substance being examined in methanol, containing (1) 2-5% w/v, ( 2 ) 0.010% w/v and After removal of the plate heat it (3) 0.0050% w/v. at 110' for one hour, place the hot plate in a closed tank containing chlorine, produced by adding HC1 to a 5% w/v solution of pot. Permanganate contained in a beaker placed at the bottom of the tank, and allow to stand f o r two minutes. Dry in a current of cold air until an area of the plate below the line of application produces at most a very faint blue colour with 0.05 ml of 0.5% w/v solution of potassium iodide in starch mucilage, avoid prolonged exposure to cold air, Spray the plate with a 0.5% w/v solution of potassium iodide in starch mucilage. Any secondry spot in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (2) and not more than one such spot is more intense than the spot in the chronatogram obtained with solution (3). 7.5.3 Biah Performance Liauid ChromatonraDhx

B.P.L.C.

High performance liquid chromatography HPLC method (3) used to estimate lomustine is carried out by using stainless steel column ( 2 0 cm X 4mm) packed with stationary phase (10um) (Nucleosil Cis) and a mixture of equal volumes of methanol and water as a mobile phase with a flow rate of 2 ml per minute at the warelength of 230 nm. 7.6

Thermal Analysis (DSCl

A differential scanning calorimetry (8) curve was obtained Fig. (7) on a Perkin-Elmer DSC-2C differential calorimeter. Nitrogen was used as the purge gas scan was performed at a rate of 25'C/min from 6O"-38O0C. The DSC curve revealed an endothermic melting peak (Max. 91.79'C).

a 33S/lV3N Thermal curve of Lomustine.

40N3

Fig. 7

!

FAHAD JABER A L - S H A M W Y

338

8.

Acknowlednements The author is highly thankful to Mr. Tanvir A. Butt, Pharmaceutical Chemistry Department, College of Pharmacy, King Saud University, who extended a lot of efforts and t a k e n great p a i n s in typing t h e manuscript. The author also appreciates the technical services provided by Mr. Babkir Awad Mustafa of the College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia.

LOMUSTINE

9.

339

Beferences

1.

"The Merck Index", 10th ed. Merck and Co., Inc., Rahway, N.J., U.S.A. 1983.

2.

"Martindale", "The Extra Pharmacopea" 28th ed. Jamee E.F. Reynolds and Anne B. Prasad. The Pharmaceutical Press, London, 1982,

3.

"The British Pharmacopoeia" Volume I. Her Majesty's Stationary Office, London p. 339, 1988.

4.

The Annual Drug Data Report, p. 132, 1979/80.

5.

"Remington's Pharmaceutical Sciences" 16th ed. , Mack Publishing Company, Easton, Pennsylvania, p. 1091, 1980.

6.

"Drug Information 88" American Society of Hospital Pharmacists, p. 522, 1988.

7.

"Cancer Chemotherapy Handbook", Robert T. Dorr; William L. Fritz, Elsevier Science Publishing Co., Inc., New York, p. 486-482, 1980.

8.

Mohammad Saleem Mian, Neelofur Abdel Aciz Mian, Unpublished Data, 1990.

9.

Martinez, Jean; Oiry, Joel; Imbach, Jean Louis; Winternity, Franscois. J. Med. Chem. 5 2 ( 2 ) , 178-82. Eng. (1982).

10.

"Martindale", The Extrapharmacopea" 29th ed. James, E.F. Reynolds. Anne and Sean. "The Pharmacetical Press, London (1989).

11.

Grossmann, A.; Reszka, R.; Arndt, D. Pharmazie, 39(10), 719 (Ger) Oct. (1984).

12. 13.

Vachek, Jaroslav; Svatek, E.; and Kakac, B. Cesk. 351-352 (in Czech.) (1982).

Farm. a ( 9 ) ,

Weinkam, Robert J. and Liv, Tsui-Yun-I J. Pharm. Sci., 71(2), 153-157 (1982).


340

14.

Smith, Ronald G.; Blackstock, Silas C.; Cheung, Lily and Loo, Ti L i . Anal. Chem., 53(8), 1205-1208

K.;

(1981). 15.

Smith, Ronald G . , and Cheung, Lily, K. J. Chromatom., 2 2 9 ( 2 ) , Biomed. ADD^., 1 8 ( 2 ) , 464-469 (1982).

16.

El-Yazig, Adnan, Martin, Cazemiro R. pharm. Res. 5 ( 4 ) ,

p. 220-225 (Eng), 1988.

LOPERAMIDE HYDROCHLORIDE Jos Van Rompay and James E. Carter

TABLE OF CONTENTS 1. Description Name, Formula and Molecular Weight 1.1 1.2 Appearance 1.3 History 2. Synthesis 3. Physical Properties 3.1 Infrared Spectra 3.2 NMR Spectrum 3.3 Mass Spectrum 3.4 Ultraviolet Spectrum 3.5 Melting Range 3.6 Differential Scanning Calorimetry 3.7 Thermal Gravimetric Analysis 3.8 Ionization Constant, pK 3.9 Solubility 3.1 0 Crystal Properties 4. Methods of Analysis 4.1 Drug Substance 4.2 Drug Product 4.3 Biological fluids 5. Stability-Degradation 6. Drug Metabolism, Pharmacokinetics 7. References 8. Acknowledgement


341

Copyright 0 1990 by Academic Presc. Inc. All rigllts 01 reproduition 111 any fom1 resew1

JOS VAN ROMPAY AND JAMES E. CARTER

342

1. DescriDtion 1.1 Name. Formula and Molecular Weiaht Loperamide hydrochloride or R 18553 '4-(4-chlorophenyl)-4-hydroxy-N,N-dimethyl-ala-diphenyl-l piperidinebutanamide monohydrochloride CAS-34552-83-5. RINN, USAN, BAN

-

4-(p-chlorophenyl)-4hydroxy-N,N-dimethyl-al~-diphenyl-l piperidinebutyranamide monohydrochloride. 'N

O\

' C

/a,

/

.HCI

,N%

C,H,CIN,O,.HCI

a

M.W.477.04+36.46 = 513.50

1.2 ADDearanCe White to slightly yellowish crystalline powder. 1.3 History Loperamide hydrochloride is an antidiarrheal synthesized in 1969 in the laboratories of Janssen Pharmaceutica, Beerse, Belgium. The synthesis of loperamide hydrochloride followed the synthesis of diphenoxylate hydrochloride (Janssen, 1956) as an antidiarrheal with less opiate like central nelvous system (CNS) activity and the discovery of fentanyl citrate (Janssen, 1960) as a potent centrally acting narcotic analgesic with antidiarrheal activity. The dissociation of the opiate-like and antidiarrheal activities resulted in a very safe and effective antidiarrheal which today is marketed in 126 countries and was recently approved for over-the-counter marketing in the United States. Loperamide hydrochloride is an USP article' and is contained in the Merck Index'. The pharmacology and biochemical properties of loperamide hydrochloride have been reviewed3.

LOPERAMIDE HYDROCHLORIDE

343

2. Svnthesis The Janssen synthesis of loperamide hydrochloride is phenyIbenzeneacet onitriIe detaiIed in Figure1'. &-(2- Bromoet hyI):ais converted through a series of reactions to N-[dihydro-3,3diphenyl -2(3H)- furanylidene -N-methyl methanaminium bromide and ethyl 4-0x0-1-piperidinecarboxylate is converted to 4-(4 chlorophenyl) -4- piperidinol. The condensation of the basic piperidine nitrogen with furanylidene results in the formation of loperamide base which is then crystallized as the hydrochloride salt. Recrystallization has resulted in the identification of two polymorphs and a tetrahydrate form which will be detailed later. Although the patent on loperamide has expired and the product is available generically other syntheses for the compound have not been published. 3. Phvsical ProDerties 3.1 Infrared SDectra The infrared spectrum of loperamide hydrochloride, polymorph I, polymorph II and a tetrahydrate form are presented The in Figure 2'. All spectra were obtained as Rbl pellets. polymorphic forms are readily distinguishable through their IR spectra. The tetrahydrate contains the characteristic OH stretch centering at 3400 cm-'. In the carbonyl stretch region polymorphs I, II and the tetrahydrate absorb at 1622 cm-' , 1601 cm-' and 1618 cm-' respectively. 3.2 NMR SDectrum The 200 MHz proton NMR Spectrum of loperamide base in CDCI, is shown in Figure 36. The spectrum was obtained with a Bruker W.P. 200 Fourier Transform spectrometer equipped with an Aspect 2000 computer with the following instrument settings: sweep width 3521 Hz; pulse angle, 30'; pulse delay, 1 sec; data points, 32,000; measuring mode, quadrature - 8 pulse sequence; temperature, ambient. The structure with proton assignments is defined in Table 1. 3.3 Mass Spectrum The mass spectrum of loperamide hydrochloride was obtained using a Varian MAT 311 instrument operating in the electron impact mode'. The spectrum was recorded using the direct inlet system at 160°C with a source pressure of 10" Torr. A current of 300 uA and energy 70 eV. The mass fragmentation


344

COOH

FIGURE 1.

Synthetic Pathway to Loperamide Hydrochloride

345


FREOUENCY (CM ') 2.5

4000

5

3Mx)

2000

1500

10

20 rm

loo0

500

10

20 pm

loo0

500

180

FREQUENCY (CM 25

4ooo

5

3ooo

2000

1500

180

FREOUENCY (CM')

FIGURE 2.

Infrared Spectra of Loperamide Hydrochloride Polymorph II and Tetrahydrate. Instrument: Perkin-Elmer Model 580B

FIGURE 3. Proton 200 MHz NMR Spectrum of Loperamide Hydrochloride Instrument: Bruker W. P. 200 Fourier Transform Spectrometer

347


Structure.

.HC1

c1 C

H

29 33

C1N 0 .HC1

Results

2 2

.

Protons

Relative

Multiplicity

J

(Hz)

Surf ace

-7.2--7.5

multiplet

2.96

broad singlet

2.68

multiplet

2.25-2.50

multiplet

1.90-2.15

mu1 t iple t

1.60

multiplet

Table 1 Structure and Proton Assignments for 200 MHz NMR of Loperamide Hydrochloride


348

behavior showing some of the possible fragmentation ions is contained in Figure 4; the mass spectrum is contained in Figure 5. The proposed structure of the base peak containing chlorine at m/e 238 is supported by the peak at m/e 240 approximately onethird in size. Likewise, the structure of the strong peak at m/e 224 is supported by the peak one third in size at m/e 226. 3.4 Ultraviolet sDectrum

The ultraviolet absorption spectrum of approximately 40 mg loperamide hydrochloride in 100 mL of 0.1 N hydrochloric The acid/2-propanol (10/90,v/v) is shown in Figure 6'. absorptions (detailed below) are the sum of the three substituted phenyl groups.

I

Maxima

253 259 265 273

532 648 581 233

3.5 Meltina Ranae Loperamide hydrochloride (polymorph I) melts with decomposition at -224°C'. Poymorph II- 218'C Tetrahydrate- 190'C 3.6 Differential Scannina Calorimetry The DSC curves of polymorphs I, II and the tetrahydrate are presented in Figures 7,8 and 9 respectively". All curves were obtained with a Dupont 910 Differential Scanning Calorimeter and a Dupont 1091 data analyzer. The instrument was calibrated using an accurately weighed amount of pure indium under the same conditions used for sample measurement (melting point of pure indium: 156.6'C; heat of fusion: 28.4 J/g). From the DSC curves the melting point of

349


c a d e 165

Cl d e 210

d e 238

d m 239

d e 224

1

-

n2°

d e 192

d c 220

1-

./a

I--

d. 194

206

1.-

d e 166

M'Y-M2

d c 56

FIGURE 4.

Mass Fragmentation Hydrochloride

d. 4 4

Ions

for

Loperamide

350


t m

c '

FIGURE 5.

Electron Impact Mass Spectrum of Loperamide Hydrochloride Instrument: Varian MAT 311


35 1

1.8 8. 88

8.88 8.78 0.60

0.58

0.40 8.30 8.28 8. 18 8.8

FIGURE 6.

Ultraviolet Absorption Spectrum of Loperamide Hydrochloride Instrument: Hewlelt Packard 8450A

0

0

a,

n

2.

zz

Y

I a

CD

h

53

-0

; r

(D

5 m

-

-

-

-

-e

-7-

-

-6--

-5-

-4-

-3-

-2-

198

-7 + \\

aRB

:

:

284

:

:

:

:

V2.a

2#B

:

Program I n t r r a o t i v r DSC

Ratrm 5 DEG/MIN

r

5

Samplrr R18553 V828-156 PRESS S 1 t - r 2.669 MG

n -.

:

:

:

:

:

2?&UO-C 2kO-C

:

1-OOC-82

:

:

229

:

:

232

:

:

O p r r a t o n JDI Plottrch 1-Oat-82

216 22R 224 T r a p r r a t u m . More detailed information about single reaction steps could be found in literature Cd,2,8-2O>.Pure optical antipodes of metipranolol were isolated from racemic base by enantioselective crystallization with mandelic or tartaric acid C 4 > . OCOCHB CH3

CCH3C0120

CZn3

’

HsC

@

CHB

OH

OCOCHs

1

2

NHa

OCOCH 3+

@CHCHCH2C1

OH 3

4

HzNCH

OCOCH

\ CH3

OCHz CHCHzNHCH AH

\

CH3

8

Fig.8 Reaction scheme of metipranolol base

383

METIPRANOLOL

5.Stabilit.y From t h e preliminary short-term s t a b i l i t y test C d d ) it should be noted t h a t metipranolol quickly decomposes i n a l k a l i n e C N a O H l and oxidizing C Hz02> solutions. Deacetylmetipranolol as a m a i n product of alkaline hydrolysis is a l s o p r i m a r y metabolite. Metipranolol s e e m s t o be r e s i s t e n t a g a i n s t a c i d i c hydrolysis i n diluted hydrochloric and a c e t i c acid solutions. The exposition t o UV l i g h t CHg-lamp, h 258 nml accelerates s i g n i f i c a n t l y the max

decomposition of metipranolol i n w a t e r solution and also i n substance. Long t e r m s t a b i l i t y test t h e confirmed excellent s t a b i l i t y of t h e substance and 40 m g t a b l e t s stored under various thermal conditions C 5 , 25, 38 and 60°C> f o r t h r e e y e a r s . In all regimes t h e sum of decomposition products C deacetylmetipranolol C DAT3, trimethylbenzochinone C TMBll did not exceed t h e l i m i t declared. L e s s favourable is t h e s t a b i l i t y of metipranolol fumarate 1% e y e drops. An increase i n content of decomposition products with increasing temperature and t i m e of exposition is evident from table V. Tab.V S t a b i l i t y of metipranolol fumarate 1% e y e drops Exposition [days1

1

*

Temperature “CI

0

25

0.059

0.002

40

25 38 60

0.085 0.125 0.316

0.006 0.015 0.034

90

25 38 60

0.144 0.190 0.400

0.012 0.029 0.050

180

25 38 60

0.130 0.204 0.453

0.019 0.043 0.068

365

25 38 60

0.145 0.315 0.908

0.029 0.058 0.086

J&f WHNAL ETAL.

384

Tab.V C continued3 Exposition Cdaysl

*

I

Temperature C"C1

730

25 38

0.193 0.246

0.032 0.043

1095

25

0207

0.058

Determined spectrophotometrically

6 . Pharmacology

Metipranolol was characterised as highly potent @-blocker with little intrinsic P-stimulating activity.The relations between some biological and physical-chemical properties in series of derivatives of metipranolol were found C 12,133. P-adrenolytic activity decreases with increasing lipophilicity . Correlation between partition coefficients and the P-adrenolytic activity of metipranolol and its analogues was experimentally confirmed C M > . The effect of.metipranolol on metabolic variables in patients with ischemic heart disease, hyperkinetic syndrome, hyperthyreosis and in healthy subjects after sympathetic stimulation was widely studied. Metipranolol administered orally decreases heart rate C35,26> and prolongs systolic time intervals C 3 7 . 1 8 ) . The antiarrhythmic effect of metipranolol in comparison with tr imecaine was tested on the ventricular fibrilation threshold in anesthetized closed chest dogs. The study of bronchopulmonary and cardiovascular effects confirmed that metipranolol significantly increases the pulmonary resistence C 1 9 J . T h e ability of metipranolol to reduce blood pressure was experiment-ally confirmed on a group of hypertensive patients C 2 0 > . The antihypertensive effect was m o r e pronounced with combination of metipranolol and butizide. Metipranolol can substantially reduce post-operative ocular hypertension (21.22). Elevated intraacular pressure after cataract extraction was decreased by 0.6% metipranolol eye drops administered before and during the first days after surgery. The effect of

385

METIPRANOLOL

i n t r a o c u l a r pressure decrease supporting t h e normalisation of i n t r a o c u l a r l i q u i d c i r c u l a t i o n m a y be successfully u t i l i z e d i n medical t r e a t m e n t of glaucoma C23,24>. Metipranolol and o t h e r P-blockers found t h e i r a p p l i c a t i o n a l s o i n neurology and psychiatry as neuroleptic a g e n t s . S t a t e s of depression, a n x i e t y , tremor and mania o r i g i n a t e d i n psychosomatic disorder could be positively a f f e c t e d by adminis t r a t i o n of metipranolol C25). Since metipranolol h a s been introduced i n t o c l i n i c a l p r a c t i c e t h e complex of secondary metabolic changes i n exposed organism w a s described. Important is t h e i n f l u e n c e on t h e a c t i v i t y of adenylcyclase enzyme which a c c e l e r a t e s t h e format ion of cyclic adenosinemonophosphate C26.27). Such equilibrium s h i f t alters t h e metabolism of glycides and l i p i d e s . S i g n i f i c a n t decrease i n glucose l e v e l s i n human blood a f t e r t h e adminis t r a t i o n of metipranolol w a s observed C 2 8 > and explained by blocking e f f e c t on t h e e f f i c a c y of i n s u l i n . Increase i n human plasma l e v e l s of growth hormone and s e c r e t i n w a s found C29).

7,Dosage

- Dosage Forms

Recomended t h e r a p e u t i c doses are summarised i n table V I . 30 Tab.VI Therapeutic doses

Single Daily

Intravenous

0.01 - 0.04 g 0.001 - 0.002 g

Oral Intravenous

0.01 - 0.08 g 0.001 - 0.004 g

Oral

The experimental use of various m i x t u r e s of metipranolol with o t h e r biologically a c t i v e components w a s described. Summary and b r i e f c h a r a c t e r i z a t i o n .of mixtures t e s t e d is given i n table V I I .

Jrlcf DOHNAL ETAL.

386

Tab.VII Metipranolol mixtures Components

I

Note

I Ref.

Metipranolol-Clopamide

Anti-hypertensive composition

TorratR 17Z4 16-03-61 Metipranolol-Butizid

Anti-hypertensive composition

Metipranolol-Butizid -Dihydralazin

Combined @-blocking, 33 diuretic and vasodilatating effect for hypertendon treatment

Met ipranolol-Butizid dihydralazin-C Methyl dopa-Spironolacton)

Combined treatment of hypertension

34

Metipranolol-Pilocarpin

Improved effect of intraocular pressure reduction

35

Metipranolol-Isosorbide-&nitrate

Amplified suppression of acute angina pectoris manifestations

36

8. D r u g

20.32

Metabolism and Pharracokinetics

Orally administered metipranolol is rapidly and almost completely absorbed. In normal volunteers, administration of met ipranolol C 20-40 mgl produced blood levels of 1-3 pg/mL in 20-30 min CiS,37). The blood levels decreased with a half-life of 17 min whereas the urinary exertion proceeded with a half-life of 1-3 hours. The P-blocade due to 10 or 20 mg of metipranolol starts at 20-30 min and is extended at least up to 12 h following oral administration C382. Kinetic parameters depend strongly on type of pharmaceutical formulation administered. The comparative pharmacokinetic study proved statistically significant prolongation of half-1if e time and @-blocking effect after administration of experimental

387

METIPRANOLOL

slow-release p r e p a r a t i o n C39>. Elimination is mainly b y biotransformation i n t h e l i v e r . Metipranolol is almost, completely and v e r y rapidly metabolized t o a deacetylated of metabolite C57193-14-33 C 4 0 > . Urinary excretion unchanged drug is approximately 4% of t h e dose ( 4 2 ) . A s proved on normal volunteers and p a t i e n t s with kidney i n s u f f i c i e n c y t h e r e n a l clearance of doacetylated metabolite decreases and t h e t e r m i n a l h a l f - l i f e of t h e metabolite i n c r e a s e s as t h e degree of kidney i n s u f f i c i e n c y grows (42). Maximum i n blood serum concentration occurs at 1.1 h a f t e r admini strat ion.

9.Methods of Analysis 9 . 2 . Identification

According t o o f f i c i a l compendiumC43) t w o i d e n t i f i c a t i o n t-ests are recomended. a 3 About 0.05g of metipranolol is mixed with 1mL of concentrated H2S04, yellow-green coloration appears. By adding ldrop of concentrated

HNO,

i n t e n s i v e brown t o red c o l o r a t i o n appears. By d i l u t i n g with 5.0 mL H 2 0 t h e s o l u t i o n t u r n s yellow and p r e c i p i t a t e s . b3 About 0.lg of meti.pranolo1 mixed with 5 m L of d i l u t e d NaOH s o l u t i o n is warmed i n w a t e r b a t h for 15 minutes. Then t h e s o l u t i o n is d i l u t e d with 5 m L of w a t e r . cooled and a c i d i f i e d with d i l u t e d H2S04.By adding two drops of f r e s h

K [FeCCN361 s o l u t i o n and two drops of 3

FeC13

s o l u t i o n , i n t e n s i v e blue c o l o r a t i o n appears.

9 . 2 . Spect r o p h o t omet r y

W e l l defined absorption m a x i m u m s e e m s t o be

388

JIftf DOHNAL ETAL.

convenient for direct spectrophotometric assay of metipranolol in substance and various pharmaceutical formulations. Nevertheless the choice of optimal wavelength ensuring maximum selectivity and high sensitivity may be critical due to possible peak coincidentions of metipranolol, its impurities and degradation products or other absorbing components from placebo. Metipranolol has been determined spectrophotometrically in methanol C Amax--297.5nm,concentration range 20-320 pg/mL> 0.1M H2S04 in water CX =277nm,concentration range 20-400 C(g/mL3 and max 0.1M NaOH in water-methanolic C 1+91 solution CXU l a X =238nm,concentration range 5-85 pg/mL or Xmax =296nm,concentration range 15-240 pg/ml> C44,45>. Spectrophotometric determination based on the quantification of quinone a5 a product of oxidation of metipranolol with KBrOB or CeC SO4l2 C 4 6 > made it possible to determine low concentrations of met ipranolol and deacetylmetipranolol in biological material. An introduction of suitable pre-extraction step together with alcaline hydrolysis prior to the measurement Cformation of deacetylderivativel makes it possible to determine accurately the levels of metipranolol in the mixture with chlorthalidon and DH-ergocrystinC47).

9.3.Chromatographic Met hods

Sensitive and selective chromatographic techniques were used predominantly for analytical evaluation of complicated pharmaceutical formulations without sample pre-treatment and for monitoring of drug serum levels for the purposes of pharmacokinetic studies.

9.3.i. Paper and Thin L a y e r

Both techniques were utilized for identification and semiquantitative estimation of

METIPRANOLOL

389

m e t i p r a n o l o l a n d its d e a c e t y l d e r i v a t i v e i n s u b s t a n c e a n d d r u g f o r m u l a t i o n s C 4 8 ) . C o m m o n l y used c o n d i t i o n s for separation are g i v e n i n table VIII. M i c r o g r a m q u a n t i t i e s of m e t i p r a n o l o l w e r e successf u l y d e t e r m i n e d t h r o u g h TLC separation and f l u o r i m e t r i c d e t e c t i o n of d a n s y l d e r i v a t i v e C.49). T a b . V I I 1 C o n d i t i o n s for t h e s e p a r a t i o n m e t ipranolol

I

Paper c h r o m a t o g r .

I

of

TLC

Sample preparat.

1%e t h a n o l i c sol.

2% ethanolic sol.

stationary phase

Whatman 4 impregnat e d w i t h 40% E t O H s o l u t i o n of f o r m a m i d e a n d 5% a r n m o n i um forrnate

Kieselgel GF/'254/' WOELM-2 plates

mobile phase

chloroform

Chlorof orm-methanolacetone-acetic acidwaterC 50 :102 0 :105 1

detect ion

1 1 U V 2 5 4 q u e n c hi n g

11U V 2 5 4 q u e n c h i ng

2 l S p r a y i n g wit-h 8%' p h o s p h o m o l y b d e n ic a c i d i n EtOH 3lSpraying w i t h D r a g e n d o r f f agent

2 l S p r a y i n g w i t h acid i c p o t a s s i u m perm a n g a n a t e solution 3jSpraying w i t h FeC13 +K3 EFeC CN16 3

w a t e r soluteion 4 3 D e n s i t o r n e t r y C 47 >

9.3.2.H i g h Per forrnance Liquid A s e n s i t i v e , s e l e c t i v e a n d reproducible assay for s i m u l t a n e o u s d e t e r m i n a t i o n of r n e t i p r a n o l o l a n d it,s a c t i v e m e t a b o l i t e a - h y d r o x y m e t i p r a n o l o l in p l a s m a w a s described C 5 0 J . T h e whole a n a l y t i c a l procedure consists of e x t r a c t i o n s t e p a n d HPLC a n a l y s i s on 5 p m silica B / 5 s t a t - . i o n a r - y phase u s i n g h e x a n e - isopropanol-methanol -concentrated a m m o n i urn

390

JM DOHNAL E T A L

hydroxide C 850:100:50:13mixture as mobile phase. When analysed on reversed phase HPLC columns it is recomended to suppress positive charge of the molecule of metipranolol in order to obtain sharp, non-difussion peak. Ion pair HPLC on reversed phase with 1-heptanesulfonic acid as a counterion proved to be suitable for the resolution and quantitative evaluation of metipranolol and other structurally related @-blockers in the mixture (59). Complete resolution of metipranolol and its deacetylderivative could be achieved on pBondapak Cie column using acetonitrile-water C l:l> mobile phase with added 1-hexanesulfonic acid as a counterion C52). Simple simultaneous determination of propranolol , metipranolol and atenolol on LiChrosorb Ck8 10pm stationary phase using phosphate buffer with octyl sodium sulfate as mobile phase has been described (53). Separation of metipranolol enantiomers after preparation of diastereomeric derivatives with symmetrical anhydrides of Boc-L-Ala and Boc-L-Leu was described C 5 4 ) . Proposed experimental conditions C stationary phase-pBondapak Cie; mobile phase-phosphate buffer pH 3.0 with the addition of acetonitrile3 made it possible to monitor serum levels of both enantiomers for pharmacokinetic purposes.

9 . 3 . 3 .Gcls Chromatography

Gas chromatography was used for monitoring of drug levels in various biological fluids. Simple determination of underivatized met ipranolol and propranolol in urine after extraction with organic solvent C petroleum ether - 2-methylbutanol ; 7:33 has been reported (55). The use of sensitive EC detector requires suitable derivatization step prior to GC. Met ipranolol has been converted to electron-capturing derivatives with methyld ichlorophosphine and sulfur C56) or ~,4-dichlorobenzeneboronicacid C 3,Ei-bisC trifluoromethyllbenzeneboronic acid3 (57). I n another procedure metipranolol was transferred to perf luoroacylderivatives with trifluoroacetic

391

METIPRANOLOL

anhydride or N-heptaf luorobutyrylimidazole C58.59). Retention indices of metipranolol, some other (3-adrenolyticsand their perf luoroacylderivatives were published (60). Direct enantiomeric resolution of metipranolol racemate derivatised with phosgene to corresponding 2-oxazolidone was achieved on chiral polysiloxane XE-60-1-valine-C W-a-phenylethylamide stationary phase (613.

9.4.Titrat ion

-

Electrochemical Determination

Metipranolol may be assayed in acetic acid containing KBr and HC1 by titration with 0.1N KBr03. The endpoint is determined biamperometrically using double Pt electrode C 4 8 ) . This method proved to be sufficiently selective and suitable for the determination of metipranolol in substance. various pharmaceutical formulations and also in biological mater ialC46). Direct voltametric determination of metipranolol C I3 and deacetylmetipranolol C 113 based on the anodic oxidation on a graphite electrode has been described (62). Determinatio-% of I-tan be done in a concentration ra-Y e 9.10 to 1.10 @ol/L and of I1 in a range 1.10 to 1 .5.10- mol/L.

9.5.Determination of Trimepranol and i t s Metabolites in Biological fluids

In addition to cited and briefly described standard GC and HPLC techniques, gas chromatography-mass spectrometry C GC-MS3 combination has been utilised for monitoring and identification of metipranolol and its metabolites in biological fluids. A typical analytical procedure consists of extraction and derivatization step C obviously trifluoroacetylationl followed by GC separation and on-line detection using quadrupole mass spectrometer. Due to the high biological background it is

392

JIRf DOHNAL ETAL.

advantageous t o use chemical i o n i s a t i o n mass spectrometric method producing high-mass molecular i o n s of g r e a t e r r e l a t i v e i n t e n s i t i e s t h a n electron- i m p a c t m a s s spectrometry. Highly specif i c and s e n s i t i v e measurement of deacetylmetipranolol i n p l a s m a was achieved with methane used both as t h e c a r r i e r g a s and chemical i o n i z a t i o n r e a c t a n t C 6 3 . 4 1 ) . Metipranolol and o t h e r (3-blockers, t o g e t h e r with t h e i r m e t a b o l i t e s , w e r e d i f f e r e n t i a t e d and i d e n t i f i e d i n u r i n e by computerized GC-MS C643. Retention i n d i c e s COV-101 s t a t i o n a r y phase) and r e f e r e n c e m a s s s p e c t r a w e r e documented.

Acknowledgements The a u t h o r s would l i k e t o t h a n k M r s . M. Hajkova, ing.J. Holubek, ing.1 .Koruna, Dr.M. Peterkova , D r .M. R y s k a , and Dr .Z .Volkova C VUFB , Prague) f o r kindly provided s p e c t r a l and thermal d a t a and helpf u l l a s s i s t a n c e i n t h e i r i n t e r p r e t a tion.

10.References 1.Blaha L. ,Weichet J . ,Hodrova J . .Trcka V.:Czech. 128.471,

2 B l a h a L.,Weichet J . ,Str ibrny J .:Czech. 150.020. 3.Graichman T . ,Hermansky M.,Mrvova Z.,Pesak M.: Czech. PV 6727-87. 4.Blaha L. ,Weichet J.:Czech. 152.096. 5.United S t a t e s Pharmacopeia, 2 1 s t Rev.,p.1441, US Pharm. Conv., Rockville C Maryland) C 19853. 6 . B r i t i s h Pharmacopoeia, Vol.1. p.9, H e r Majesty’s S t a t i o n e r y Off ice London C 19883. 7.Kralova K.,Mitterhauszerova L.:Farm.Obz. 52C73, 295 C 19833.

METIPRANOLOL

8 . S n u p a r e k V . , P o l a k J.,Varga I . , K m e t t y G : C z e c h . 239.442. 9 . N e v y d a l J . ,Manduch M. , F r i m m R . , G a t t n a r O .: C z e c h . 239.4 14. 1 0 . Z o e l s s G . ,Pfarrhofer G . : G e r . O f f e n . 3544.172. 11. L a b o r a t o r y R e p o r t a n d T e c h n o l o g y P r e s c r i p t i o n , Add.10, 16 C 1 9 8 9 3 .

1 2 . Z a k h a r i S . : E u r . J . P h a r m a c o l . 2 9 C 13 Z 2 C 19743. 13.kejholec V . , K a k a c B . , K u c h a r M . , H a v l i k I . , J a n k u I . , T r c k a V..Blaha L..Weichet. J . : E x p e r i e n t i a , Supp1.23 C Quant.Struct.-Act.Relat.3,115 C 19763.

14Z a k h a r i S ., P r o n a y o v a N. .Dr i m a l J. ,Molnar L .: B r a t i s l . L e k . L i s t y 62C63.678 C 19743. 1 5 . M a y e r 0., P e t r l i k M. ,Vit.orrs J . , C e p e l a k V . : V n i t r . L e k . 22C 111,1102 C 19761. 16.Hopf R. ,Tourbier H . ,Kallenbach M.: H e r z / K r i e s l a u f 9 C 103,560 C 1 9 7 7 3 .

17.Striz S. .Inczinger F . , C a g a n S . : B r a t i r l . L e k . L i s t y 70C23,155 C 19783. 18. S m i d .J., C e p e l a k V ., M a y e r 0 .:Vn i t r .Lek . 2 7 C 7 3 , 6 8 3 C 19813.

1 9 . D r i m a l .J., S e g i n k o J . , G i b a l a P . , S t r i z o v a K.: B r a t i s l . L e k . L i s t y 70C 4 3 , 4 2 9 C 1 9 7 8 3 , 2 0 . H a y d u k K. , C h r i s t H. ,Krauss J. , H a l a n k C. .Kuehn A.: Therapiewoche 29C 4 4 3 , 7 5 2 8 , 7 5 3 0 C 19791.

21 . S c h m i t z V a l c k e n b e r g P.:Klin.Monatsbl. A u g e n h e i l k d . 182C23.150 C 1 9 8 3 3 . 22.Krieglstein G.K. ,Schrems W.:Fortschr. O p h t h a l m o l . 8 1 C 2 3 1-27 C 19843. 2 3 . H o p k i n s G.A.:Am.J.Optom.Physiol.Opt.6 1 C 121, 756 C 19843.

393

394

JIM DOHNAL ETAL.

24.Kern R.:Klin.Monatsbl.Augenheilkd.186C 63, 442 C 19853. 25.Poldinger W.:Z.Allgemeinmed.61C 1-23, 7 C 19851. 26.Dollet-yC.T.,Peterson J .W.,Conolly M.E.:Clin. Pharmacol.Ther.10. 765 C 19691.

27.Shanks R.G.:Indian J.Med.Sci. 2.351 C 19691. 28.Zamrazil V.,Felt V.,Nemec J..Vana S . : Cas.Lek. Cesk. 11lC 141,312 C 19723. 29.Nedvidkova J.,Felt V.:Cas.Lek.Cesk. 112C341,1014 C 19731. 30.Cs.Pharmacopoea,4th Rev.,Vol.III p.454,Avicenum-Zdravotnicke nakladatelstvi Praha C 19873. 31.Schuetz W.:Brit. 1417.864. 32.0verlack A.,Kolloch R.,Stumpe K.O.:Herz Kreisl. 13C73,324 C 19813. 33.Teufel W ..Rartsch W.,Glocke M.,Hacker W.: Therapiewoche 35C73.691 C 1985). 34.Smolarz A .:Therapiewoche30C 473 ,7971 C 1980). 35.Scharrer A..Ober M.:Klin.Monatsbl.Augenheilkd 189C63,450 C 19861. 36.Sponer G.,Voss E.,Dietmann K.:Med.Welt 32C 14A3, 492 C 19811. 37.Mayer 0. ,Cepelak V.,Vitous J.,Potmesil J.:Int.J. Clin.Pharmacol.,Ther.Toxico1. 18C31.113 C 19803. 38.Pentikainen P.J.,Neuvonen P.J.,Penttila A.:Int. J.Clin.Pharmacol.Biopharm.16C61, 279 C 19783. 39.Marinow J.,Akpan W..Ledermann H.,Abshagen U.: Herz Kreisl. 13C113, 548 C19813. 40.Maffei Facino R.,Bertuletti R.,Carini M., Tofanetti O.:Anal.Chem.Symp.Ser.1979 CPub.19801. 4 C Recent Dev.Mass spectrom. Biochem .Med.,61317.

METIPRANOLOL

395

41 . A b s h a g e n U. ,Betzien G. ,Kauf m a n n B. , E n d e l e G.: E u r . J . C l i n . P h a r m a c o l 2 1 C 43, Z 9 3 C 19813. 42.Tschoepe W . ,Volk J . , E n d e l e J. , A b s h a g e n U. , R i t z E.:Verh.Dtsch.Ges.Inn.Med.85,1226 C 19793. 4 3 .Cs . P h a r m a c o p o e a ,4th R e v . ,Vol .II p 363,

A v i c e n u m - Z d r a v o t n i c k e n a k l a d a t e l s t v i Praha C 19873 44 . K r a c m a r J. , A l v a r e z Sotolongo M ., K r a c m a r o v a J ., R e m s o v a M. , H o r s k a J .:Pharmazie 3 1 C 6>,363 C 19763. 4 5 . K r a c m a r J. . A l v a r e z Sotolongo M. , K r a c m a r o v a J . , H o r s k a J ., P e t r a n o v a J. . M o r a v c o v a B.:Cesk . F a r m . 2 5 C 7 3 , 2 4 3 C 19763.

4 6 . J a n c i k F..Kakac B. .Koerbel J . : C z e c h . 172.228. 4 7 . P e t e r k o v a M . , K a k a c B. ,Matousova O.:Cesk.Farm. 2 9 C 7 3 , 2 4 1 C 19803. 48.The S c h e m e of O b l i g a t o r y E s t i m a t i o n 60-Tr i m e p r a n o l Subst. VUFB , Praha C 19713.

49.Schulz H.G. , Z a p k a R . : F r e s e n i u s ' 2 . A n a l . C h e m . 323 C2>,1€32C 19863. 50.Paulter D.B. , . J u s k o W .J .:J . C h r o m a t o g r . 228,215 C 19823.

51.Lef e b v r e M.A .. G i r a u l t J . .Fourt i l l a n J .B.:J . L i q . C h r o m a t o g r . 4,483 C 1 9 8 1 3 . 5 2 . V i d a l E . , G u i g u e s M..Balansard G . , E l i a s R.: J . C h r o m a t o g r . 348,304 C 19851.

5 3 . W i n k l e r H . , R i e d W..Lemmer 22.3 C 1 9 8 2 2 .

B . : J . C h r o m a t o g r . 228,

5 4 . H e r m a n s s o n J.,Von B a h r C . : J . C h r o m a t o g r . 227.1 13 C 19823. 5 5 . V o n M e y e r L . . D r a s c h G . , K a u e r t G . , R i e d l L., R i e d l A . : B e i t r . G e r i c h t l . M e d . 37,363 C 1 9 7 9 3 . 56.Jacob K. S c h n a b l G. , V o g t W . : C h r o m a t o g r a p h i a 19, 216 C 1984>.

57 .Poole C .F. ,Johansson L. , V e s s m a n J .:J. C h r o m a t o g r . 194,365 C 19801.

JIkf DOHNAL ET AL.

396

5 8 . Q u a r t e r m a n C . P . , K e n d a l l M . J . , J a c k D.B.: J . C h r o m a t o g r . 183,92 C 19801. 5 9 . K i n n e y C.D.:J.Chromatogr.

2251,213 C 19813.

60 .Mark0 V .:Chem .Pap. 42C 33,375 C 19881. 61.Konig W .A. , E r n s t K . , V e s s m a n J . : J . C h r o m a t o g r . 294.423 C 1 9 8 4 3 .

6 2 . P r o k s a B. ,Molnar L . : P h a r m a z i e 29C63,418 C 19741. 6 3 . E n d e l e R. ,Senn M . , A b s h a g s n U . : J . C h r o m a t o g r . 227, 187 C 1 9 8 2 3 . 64 .Maurer H. ,Pfleger K.:J . C r o m a t o g r .382,147 C 19863.

NIZATIDINE Timothy J. Wozniak Lilly Research Laboratories Eli Lilly and Company Indianapolis, Indiana 46285

ANALYTICAL PROF'ILES OF DRUG SUBSTANCES VOLUME 19

391

TIMOTHY J. WOZNIAK

398

TABLE OF CONTENTS 1 . Description Name, Formula and Molecular Weight 1.1 1.2 Appearance, Color and Odor 1.3 History 2. Synthesis 3. Physical Properties 3.1 Infrared Spectra 3.2 Nuclear Magnetic Resonance Spectra 3.3 Mass Spectra 3.4 Ultraviolet Spectra 3.5 Melting Range 3.6 Differential Thermal Analysis 3.7 ThermogravimemcAnalysis 3.8 Crystal Properties, Polymorphism 3.9 Solubility 3.10 Partition Coefficients 3.1 1 Ionization Constant, PKa 4. Methods of Analysis 4.1 Identity 4.2 Elemental 4.3 Ultraviolet 4.4 Chromatographic 4.41 Thin-layer 4.42 High-PerformanceLiquid

5. Stability - Degradation 5.1 Potential Routes of Degradation 5.2 Solid State Stability 5.3 Solution Stability

6 . Drug Metabolism and Pharmacokinetics 7 . References 8 . Acknowledgments

399

NIZATIDINE

1. DESCRIPTION 1.1 Name, Formula and Molecular Weight Nizatidine is marketed by Eli Lilly and Company under the trade name, Axid@. It was referred to as LY139037 in the early literature. Chemically it is known as N-[2-[ [ [2-[(dimethylamino)methyl]-4 thiazolyl] methyl] thio] ethyl] -N-methyl-2-nitro-1,l-ethenediamine. The CAS Registry Number is 76963-41-2. Empirical Formula:

C 2H2 N502S2

Molecular Weight:

33 1.46

Structure:

1.2 Appearance, Color and Odor Nizatidine is an off-white to buff crystalline solid. A slight sulfurmercaptan odor may be present. 1.3 History Nizatidine is a specific, potent H2-receptor antagonist (1-2). Unlike cimetidine, which contains an imidazole ring structure, or ranitidine, which contains a furan ring structure, nizatidine has a thiazolyl ring structure. This structure is more potent than cimetidine in inhibition of gastric acid secretion induced by various stimuli and,lacks cimetidines's anti-androgenic and hepatic microsomal enzyme inhibiting effects (3-6). The drug substance has been used in the treatment of duodenal ulceration. Nizatidine is administered as a 150 mg or 300 mg capsule.

400

TIMOTHY J. WOZNIAK

2. SYNTHESIS

The cyclization of dimethyarninothioacetamide (I with ) ethyl bromopyruvate (II) in refluxing ethanol gives ethyl 2-(dimethylarninomethyl)4-thiazolecarboxylate@ which I)is ,reduced with lithium triethylborohydride in tetrahydrofuran yielding 2-(dimethylaminomethyl)-4-thi~lemethanol (IV). The condensationof (IV) with 2-aminoethanethiol(V) by means of 48 percent hydrogen bromide affords 2-(dimethylaminomethyl)-4-(2-aminoethylthiomethyl) thiazole (VI),which is finally condensed with 1-(methylthi0)-2nitro-N-methylethyleneamine in water (7). The synthesis is illustrated in Figure 1.

- 0

(cH3)2NcH2

y>

C02CH2CH3 + Li(CH2CH3)sH

-m

0

y>

(CH3)2NCH2

CH2OH + HSCH2CH2NH2

N

03

r> r>

(CH3)2NCH2

(CH3)2NCH2

HBr

-0

cHN02 II CH2SCH2CH2NH2+ CH3SCNHCH3

cHN02 II CH2SCH2CH2NHCNHCH3 Nizatidine

Figure 1 . Chemical synthesis for nizatidine.

+

401

NIZATIDINE

3. PHYSICAL PROPERTIES 3.1 Infrared Spectrum The infrared spectrum for nizatidine as a potassium bromide pellet is illustrated in Figure 2. The spectrum was recorded on a Nicolet Model 5SXC Fourier Transform infrared spectrophotometer. The major adsorption bands for the infrared frequencies and the corresponding assignments are listed in Table I. The infrared spectra of nizatidine in a variety of solvents at room temperature indicate the presence of two species in solution (8-9). These species differ most in the region of the nitroketaminal group and have been confmed to be cis/trans isomers around the double bond. This is evidenced by the presence of both intramolecularly non-bonded and H-bonded N-H structure in nonprotic solvents @).The hydrogen-bonding observed in the infrared spectra was found to involve the nitro group. The absence of a C=C stretch provides additional information regarding the delocalization of the electrons in the nitroketaminal system. Such delocalization is consistent with the ultraviolet and N M R spectral data, indicating extensive delocalization of the amine nitrogen lone-pairs throughout the system. Table I. Infrared Band Assignments for Nizatidine Infrared Assignment Wavenumber, cm 3280,3210 3107 3094 2945,2860 2829,2784

NH stretch; two groups CH stretch in NO2 - CH CH stretch in thiazole ring CH stretches in NCH3, CH2CH2

1622 1587

C=C, conjugated with NO2 Asym. NO2 stretch, conjugated with C-C; thiazole ring, weak contribution

1521 1470, 1458 1435,1422

Thiazole ring CH deformation in NCH3, CH2; CN stretch

1377, 1359

Thiazole ring for one frequency is sym N02, H-bonded, conjugated.

/'

0 0

/'

I

0 0 0 O W

403

NIZATIDINE

3.2 Nuclear Magnetic Resonance The 300 MHz lH spectrum of nizatidine (100mg/mL)in CDC13 with 0.5% v/v tetramethylsilane is shown in Figure 3. The spectrum was obtained on a Varian Unity spectrometer using the following instrumental parameters: 5 mm 1W13Cdual probe; spectral width, 481 1 Hz; 50" pulse width; 64K time-domain data points; acquisition time, 6.8 seconds; 100 scans and probe temperature, 27°C . The proton-decoupled l3C spectrum of nizatidine (100 mg/mL) in CDC13 with 0.5% v/v tetramethylsilane is shown in Figure 4. The data were obtained using a 5 mm lW13C dual probe; spectral width, 20 KHz; 90"pulse width; 64K time-domain data points; acquisition time, 1.6 seconds; relaxation decay, 2.4 seconds; WALTZ-16 proton decoupling; 4000 scans and probe temperature, 27°C. The spectrum was processed with 1.0 Hz Lorentzian line broadening followed by the addition of 64K zero-fill data points. Nizatidine exists as a mixture of cis/trans isomers of the nitroketaminal moiety in solution (Figure 5). The presence of a doublet resonance at approximately 95-100 ppm in the 13C spectrum eliminates several possible tautomers. This is further supported by the occurrence of peak doubling of the N-methyl and N-methylene resonances of the nitroketaminalregion in both the 1H and 13C spectra. The group can exist in either of two conformations of similar energy, and these interconvert slowly enough to lead to doubling of many of the NMR resonances. This is evidenced by N M R and infrared studies of nizatidine at different temperatures in solution (8-9). The two hydrogen-bonded NH groups come into resonance near 10 ppm, while the nonhydrogen-bonded NH groups come into resonance in the 6-7 pprn region of the lH spectrum.

a

H

0-

I

3

-0

Figure 5. Cisltrans isomerization of nizatidine in the nitroketaminal region

a

I

im

. 404

405

d

406

TIMOTHY J. WOZNIAK

The 1H and proton-&coupled 13C NMR spectra of nizatidine at probe temperaturesranging from -3°C to 57OC (lOOmg/mL in CDCl3) are shown in Figures 6 and 7, respectively. The IH spectrum of nizatidine at 57OC shows one set of signals due to fast interconversion of the rotamers (Figure 6). When the probe temperature is lowered to -3OC, the interconversion is much slower and two sets of signals are observed for all the protons associated with the dialkylaminonitroethenegroup. Spin decoupling experiments on the two N H quartets and two NH triplets c o n b e d the assignmentsof the signals for the individual rotamers. Structural assignments for both proton and carbon nuclear magnetic resonance spectra are listed in Table III.

Table III. N M R Chemical Shift Assignments of Nizatidine at 3OC Site 2 4 5 2' N(CH3)2 6 8 9 10 11 12 13 14

'H

7.15 3.74, 3.77 2.36 3.85, 3.86 2.79 3.40, 3.49 6.72, 10.35

13

c

171.77, 172.06 152.28, 152.72 116.45, 116.59 60.77, 60.87 45.73, 45.76 30.98, 32.22 30.65, 31.24 41.04, 41.51 156.52, 156.74

7.25, 10.24 2.84, 3.00 6.63, 6.64

27.73, 29.07 98.21, 98.26

c

-

D

c

d

' Figure 7. 13C NMR spectrum of nizatidine in CDC13 at -3 "C(bottom),27OC (middle) and57"C (top).

409

NIZATIDINE

3.3 Mass Spectrum The electron impact mass spectrum of nizatidine is shown in Figure 8. The spectrum was obtained using a VG Model 7070E magnet sector instrument. No molecular ion was observed in the electron impact spectrum of nizatidine. Loss of a hydroxl radical from the molecular ion of nizatidine to yield an ion at m/z 314 is consistent with other compounds having the nitroketaminal group. The complexity of the rest of the EI spectrum was resolved by determining the accurate mass of the fragment ions to better than f 0.005 mass units. This allowed for the determination of the elemental compositions of each fragment. The ion at m/z 58 could have been (CH3)2NCH2, C2H2S or CN02 which have masses of 58.0657, 57.9877 and 57.9929, respectively. An accurate mass measurement of the m/z 58 fragment showed (CH3)2NCH2 to be the correct assignment. Several of these fragment assignments are illustrated in Table IV and Figure 9. Table IV.Mass Assignments for Electron Impact Spectrum Mass Assignment

Formula

314.110 297.102 254.068 227.054 17 1.009 11 1.015 58.063

C12H2@50S2 C12H19N5S2 Cla14N4S2 C9H13N3S2 C6H7N2S2 CsHsNS C3H8N I I

H

131

O

Figure 9. Electron impactfragmentation schemefor nizatidine.

I

100-

- x10.0

6

95908580-

x10.0

-

i 4

7570.

111

656055. 5045227

%I

I

I

I

20 15 10 5 0

297

, 1 1 1 271 288

300

Figure 8. Electron impact mars spectrum of nizatidine.

350

400

NIZATIDINE

411

The field desorption mass spectrum of nizatidine is shown in Figure 10. The spectrum was obtained using a Varian-MAT Model 731 double sector instrument. The spectrum consists of the protonated molecular ion at m/z 332 and a h e r ion at m/z 663. 3.4 Ultraviolet Spectrum The ultraviolet spectra of nizatidine in methanol and water are shown in Figure 11. Spectral acquisition was performed on a Perkin Elmer Model Lambda 6 spectrophotometerusing 1-cm quartz cells. The ultraviolet spectra in both methanol and water contain two absorption maxima, both of which are abolished by the addition of acid and restored by the addition of base. The maximum absorbance from the diaminonitroalkenechromophore occurs at 325 nm (methanol) and 314 nm (water) with molecular absorptivities of e=19,600 and e=15790, respectively. The peak absorbances for methanol and water solutions are listed in Table V. The pH dependence of the UV spectrum is critical for nizatidine. At pH values below 4.5, a hypochromic effect is observed for the chromophore assignable to the substituted conjugated diaminonitroalkene. The lack of chromophore at low pH, attributable to loss of conjugation by protonation of the nitro group-bearing carbon atom in aqueous solution and which is complete in hydrochloric acid, is shown in Figure 12. Table V. UV Absorbances and Molecular Absorptivities Methanol E l%/lcm 325

592

Water E l%/lcm 19600

314

476

11820 15790

3.5 Melting Range Nizatidine melts between 132-133OC using the USP XXII procedure for Class 1 substances. 3.6 Differential Thermal Analysis The DTA thermogram for nizatidine, at a heating rate of 5OC per minute, shows a sharp endotherm at 133°C indicating a melt. A large exotherm occurs at 180°C where the compound begins to decompose.

cu

I I

I

I

412

m toto

m

I

to v

m to+

:o

0 -0 . r

-

:o -0

:m c

:o :-o 0 o :o ;-

:o

-0 -(D

-

:o -0 : m -

:o

:-0 *

a -

to1 to

v

:o o -cu y

-

c

4

t

0

Y

Lo O

.

n

m

0 0

o

Lo

413

0

0 0 0 0

0 0

w

Lo Lo

m

% J

C

E

Y

I

x

4.

>

W

A

W

m z

In ln

N

0

cu

N

.

i 000

0.750

WAVELENGTH (nml

Figure 12. Ultravioletabsorption spectra of nizatidine, obtained atpH I (bottom),pH 2 ( lower middle), pH 3 (upper middle) and pH 5 (top).

NIZATIDINE

415

3.7 Thermopvimetric Analysis The TGA thermogram for nizatidine, at a heating rate of 5OC per minute, shows no significant weight loss through 180°C. These data are consistent with nizatidine's properties as an anhydrous and non-hydroscopic material. 3.8 Crystal Properties, Polymorphism The X-ray powder diffraction pattern of nizatidine is shown in Figure 13. The spectrum was obtained using a Nicolet powder diffractometer using copper Kairradiation (1.5418 A) with a graphite monochrometer. A total of 21 peaks were detected at scattering angles between 5 and 35 degrees 2-theta. Table VI summarizes the data from X-ray powder diffraction where d is the interplanar spacing (A), and ,&I is the relative intensity of the X-ray line. Nizatidine has been crystallized from solutions of ethyl acetate, butyl alcohol, methylene chloride and ethanol. X-ray diffraction studies indicate the presence of a single crystal form in all cases. Table VI. Powder X-ray Diffraction Data for Nizatidine D-Spacing (A) 12.59 6.36 6.11 5.98 5.72 5.46 5.25 4.43 4.38 4.18 3.98 3.85 3.71 3.63 3.42 3.36 3.33 3.22 3.07 2.99 2.88

Intensity (I.&) 0.39 0.08 1.oo .26 .ll 0.20 0.17 0.15 0.04 0.48 0.30 0.43 0.35 0.15 0.28 0.13 0.43 0.28 0.15 0.15 0.13

NIZATIDINE

417

3.9 Solubility Nizatidine is freely soluble in chloroform ; soluble in methanol; sparingly soluble in water and buffered solutions; slightly soluble in ethyl acetate and isopropanol. Nizatidine is essentially insoluble in benzene, diethyl ether and octanol. The solubility data for nizatidine are shown in Table VII. Table VII. Solubility of Nizatidine Solvent Water Buffer - pH 7.0 Buffer - pH 4.5 Buffer - pH 1.2 Isopropanol Diethyl ether Ethyl acetate Methanol octanol Benzene Chloroform

Solubility (mg/ml) 210.0 210.0 210.0 210.0 23.33 -

c33.3 460 M

Baemodalysate

59

Plouriietry

Serum or blood

60

(30 cm X 3.9 n)of

methanol (191:59:50:200).

Aq.

30% methanol.

Precolumn (11.5 a X 1.5 I) with Corasil C18 (37-50 p) t (25 a X 4 I) Zorbax PB-TMS (7 p ) .

Aq.

acetate buffer (pH 4.5)

(25 CE X 4 540.

Licl in aq. 30% acetonitrile

p Bondapak C16 +

1 mllmin

guard column of Bondapak C18lCorasil.

.P)

IBX-

+ acetate buffer: methanol (13:7).

........................ Continued

I...

Continued Table ( 7 )

...

(30 cm X 3.9 )I p Bondapak C18 + prec o l u n (2 cm X 4 )I of Bondapak-Corasil (37-50 w ) .

10 m-diauonium hydrogen: phosphate (pH 5.5 and H3P04): acetonitrile (25:3).

2 ml/iin

254 nm

Bondapah C1B

Water: methanol: acetic acid (68:21:0.1 vol/vol).

1.0 rl/iin

U.V. detect

Plaaa

61

-

62

FAHAD JABER AL-SHAMMARY ET A L

470

the mixture is agitated. It is diluted to a known volume with the extracting mixture, keeping in mind that the concentration of ribolfavin in the assay solution should not fell below the sensitivity of the method to be used for analysis. For fluorometric method, the concentration of ribolfavin should be 0.1 pg/ml. The solution is filtered. The procedure has been used for the extraction of riboflavin in multivitamin tablets, capsules, liquids and mineral dietary supplements (63). b) AdsorDtion on Purified Talc

A column 12

X 200 mm, with a stop clock connected to a suction pump is employed and a slurry of talc having a particle size 20-50 p in water, sufficient to form about an 80 mm bed is poured into the column. A flow rate of about 4-6 ml/minute is maintained by adjusting the suction. The diluted sample is allowed to pass through the talc column followed by a sufficient volume of 0.01 N HC1 and 10% Dioxan in order to elute other constituents adsorbed on the talc. The yellow-coloured band of riboflavin adsorbed on the talc bed from the assay sample is then eluted with 10 ml of 20% dioxan. The determination of the amount of riboflavin thus eluted by a spectrophotometric method by the diluting the above solution to a volume containing 1 mg/100 ml and then measuring the absorbance of the yellow colour at 267, 374 and 445 mp (64).

8.13

Thermal Analysis (DSC)

A DSC (differential scanning calorimetry curve) of riboflavin was obtained'Fig. (7) on a Perkin Elmer DSC-2C differential calorimeter. The analysis was conducted under Nz atmosphere, at a scan rate of 25'C/min. The DSC curve revealed an endothermic melting peak max. 309.61"C. 9.

Acknowledptements The authors are highly thankful to Mr. Tanvir Ahmad Butt, Pharmaceutical Chemistry Department, College of Pharmacy and Mr. Babkir Awad Mustafa, College of Applied Medical Sciences, King Saud University, Riyadh

RIBOFLAVIN UTs

I

3.20 mg

SCAN RATED

MAXD 389.81

25.00 drg/rnin

PEAK FROMD 301.23 101 313.88 ONSETD 307 CAL/CRAk 33.77

FXLEI OSAK.U4

TEMPERATURE (C>

DSC

FAHAD JABER AL-SHAhfMARY ETAL.

412

for, their sincere help in the preparation of this manuscript. 10. References 1.

"The British Pharmacopoeia" Her Majesty's Office (1980).

Stationary

2. "Martindale" The Extra Pharmacopoea" 28th Ed. Eds, J .E. Reynold and A.B. Prasad. The Pharmaceutical Press London ( 1982). 3. "Merck Index" 10th Ed, Merck and Co., Inc. Rahway, N. J. U.S.A. (1983). 4. R. Kuhn, H. Rudy, F. Weygand,

5. R. Kuhn, H. Rudy,

&. a,625 (1935).

&. a,169 (1935).

6. Drug Information 88, p . 2101, American Society of Hospital Pharmacists, 1988.

7. C.C. Tsong, J, Fermentation Technol. (Japan) 2, 56, 187 (1946) [C.A. 44, 59751. 8. W.J. Peterson, F.M. Haig, A.O. Shaw. J. Am. Chem. SOC. 66, 662, 1944. 9. R. Posternack and E.U. Brown, U.S. 20, 1944) [C.A. 3,221, 19441.

Pat. 2324800 (July

10. Textbook of Biochemistry by Mohammad Rafique Khan, p. 433, 1972. Shan Electric Press, Lahore, Pakistan.

11.

Remington's Pharmaceutical Sciences, 1 3 t h Ed. p . 1099-1100, Mack Publishing Co, Easten, Pennsylvania, 1965.

12

M. Tishler, J.W. (1945).

0

Wellman, J. Am. Chem. SOC.,

u,

2165

13. The vitamins Vol. 111, W.H. Sebrell, Jr and Robert S. Harris, Academic Press, Inc. New York (1954). 14. One, Shigeru; Hirano, H, Oahthalmic Res. 15(3), 140-5 (1983).

473

RIBOFLAVIN

15. P i n t o , J o h n ; Huang, Yee P i n g ; R i v l i n , R i c h a r d S. C l i n . I n v e s t . 6 7 ( 5 ) , 1500-6, 1981.

JI

16. Gajewska, Maria; and S z r a j b e r , Zofia. Chemia a n a l i t . , 20(1), 99-106, 1975. ( P o l i s h ) .

17. M . H .

Hashmi, A.J. A j m a l , T. Q u r e s h i and A . Mikrochim. Acta 1, 30-35 (1969).

18. E.V. Rao and M.N. (1968).

Narayanan, I n d i a n J .

Rasheed,

Pharm. 30, 70

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and Ismaiel,

S.A.

21. Werner, W.; and G a n i , A . F r e s e n i u s ’ Z. Anal. Chem., 300(5), 416 (1980). 22. Macpherson, A.M.D. ; and O t t a w a y , J.M. (1229), 830-836 (1978). 23. S c h e r t e l , M.E.; a n d S h e p p a r d , A . J . 60(7), 1070-1074 (1971). 24.

Analyst,

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F a r r o h a , S a b r i , M.; and L i n d q u i s t , J . B u l l . Coll. S c i . , ( U n i v e r s i t y Baghdad, I r a q ) , l3(2), 287-304 (1975).

25. Jozan, Miklos; S z a s z , Gyorgy; and Szemeredy, K a t a l i n . Acta. Pharm. Hung., 50(4), 153-160 (1980). 26. Knobloch, E.; Hodr, R.; J a n d a , J . ; Herzmann, J . ; and Houdkova, Vera. I n t . J . Vitam. N u t r , Res., 49(2), 144-151 (1979). 27. Rashid, I n a y a t ; and P o t t s , Donald. J. Food S c i . , 45(3), 744-745 (1980). and Bashor, 28. T i l l o t s o n , J . A . ; 107(1), 214-219 (1980).

29.

M.M.

Anal.

Biochem.,

Chausovskii, S.S.; and Gaule, Yu. A. Farm. Zh.

3, 18-19 (1982).

(Kiev),

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30. G.S. Cha and M.E. Meyerhoff. J . Anal. Biochem., 216 (1988). 31.

168,

Fazekas, Arpad G.; Menedez, Carlos E.; and Rivilin, Richard S. Biochem. Med. 9(2), 167-176 (1974).

32. Lotter, S.E., Miller, M.S., Bruch, R.C., and White, H.B. 111.; Anal. Biochem., m ( 1 ) , 110 (1982). 33 *

Watanabe, Hyozo. JaDan Analyst., 19(12), 1658-1663 (1970).

34. Ismaiel, Saad A. Analyst, Lond. 97, 644-646 (1972). 35. Jaumann, G. ; Engelhardt, H. ChromatoRraDhia, 615-17 (1985).

a(lo),

36. E.S. Reyes, K.M. Norris, C. Taylor and D. Potts. J. Assoc. Off. Anal. Chem., 7 l , 16 (1988). 37. Kraemer, U.; Bitch, R.; and Hoetzel, Klin. Wochenschr 55(5), 243-244 (1977). 38 39

Thielemann, Horst. Pharmazie, 35(2), 125 (1980). 0

40.

G. Tortolani, V . Montovani and P. Bianchini. Boll. SOC. Ital. Biol, SDer. 47(6), 163-165 (1971).

Haworth, C.; Oliver, R.W.A.; and Swaile, R.A. Analyst. 432-436 (1971).

m.,s,

41. Mansourian, R. Barclay, D. and Dirren, H. Int. J. Vitam. Nutr. Res. 52(2), 228 (1982).

42. Fellman, J.K., Artz, W.E.; Tassinari, P.D.; Cole, C.L., and Augustin, J. J. Food Sci., 47(6), 2048-2050 (1982). 43.

Yasudo, Kazuto; Ikeda, Ritsuko; and Kawada, Akiko. Rinsho Byori, 29(6), 564-568 (in Japanese), 1981.

44. Walker, M.C.; Carpenter, B.E. and Cooper, E.L. Pharm. Sci. 70(1), 99-101 (1981).

JI

45. Bognar, Antal. Dtsch. Lebensm. Rundsch. 77(12), 431-436 (in German), 1981.

RIBOFLAVIN

46.

475

Kwok, Roderic, P . ; Rose, W.P., Tabor, Rick and Pattison, Thomas S. J. Pharm. Sci., m ( 9 ) , 1014-1017, (1981).

47

1

48. 49 * 50.

Skurray, Geoffrey, R. Food. Chem. 1 ( 2 ) , 77-80 ( 1 9 8 1 ) . Ang. Catharina, Y.W.; and Moseley Frederick, A. J. Agric. Food Chem. 2 8 ( 3 ) , 483-486 (1980). Kirchmeier, R.L.;

67(10),

and Upton, R.P.

J. Pharm. Sci.

1444-1446 (1978).

Callmer, K.; and Davies L. ChromatoRraDhia; 1(11), 644-650 (1974).

51.

Kneifel, W, Dtsch. Mo1k.-Ztg, m ( 9 ) , 212-213 ( 1 9 8 6 ) .

52.

Ichinose, Norio; Adachi, Kyoko; Schwedt, Georg. Analyst. Lond. m(12),1505-8 (1985).

53.

Wittner, D.; and Haney, W.G. Jun. J. Pharm. Sci., 6 3 ( 4 ) , 588-590 (1974).

54

Flondi, A.; Fini, C., Palmerini, C.A.; and Rossi, A. Riv, Sci. Tecnol. Alimenti nutr. Um., 6 ( 4 ) , 197-203 (in Italian), 1976.

55.

Smith, Marilyn Dix, J. Chromatogr. m ( 3 - 4 ) ,

Biomed;

Appl. 8 ( 3 - 4 ) , 285-291 (1980). 56.

Yagi, Kunio, and Sato, Michihiko, Biochem. Int. 2 ( 3 ) , 327-331 (1981).

57. 58. 59.

Lumley, I.D.; and Wiggins, R . A .

106(1267),

Analyst (London),

1103-1108 (1981).

Gatautis, Vytenis, J . ; and Naito, Herbert, K. Clin.

m. (Winston-Saleem N.C.),

2 7 ( 1 0 ) , 1672-1675 ( 1 9 8 1 ) .

Mohammed, Hussain Y, Veening, Hans; and Dayton, David A. J. Chromatogr. = ( 2 ) , Biomed. Appl. 1 5 ( 2 ) , 471-476 (1981).

60.

Ohkawa, Hiroshi, Ohishi, Nobuko; and Yagi, Kunio, Biochem. Int. 4 ( 2 ) , 187-194 (1982).

FAHAD SABER AL-SHAMMARY ETAL.

476

61.

Pietta, Piergiorgio; Calatroni, Almo and Rava, Angelo, J. Chromatoar. m ( 2 ) , Biomed. Appl. 1 8 ( 2 ) , 445-449 (1982).

62.

Ashoor, S.H. Seperich, G . T . , Food Sci., u(1), 92 ( 1 9 8 3 ) .

Monte W.C., Welty J., L

63. M.J. Deutsch, H.C. Pillsbury, S.S. Schiaffino and H.W. Loy, J. Assoc. Offic. A m . Chemists, 43, 42 ( 1 9 6 0 ) . 64.

N . Wahba and E. Fahmy, J. Pharm. Pharmacol., l7, 489 (1965).

ANALYTICAL PROFILE OF SCOPOLAMINE HYDROBROMIDE

FaridJ. Muhtadi and Mahmoud M A Hassan

Department of Pharmacognosy, College of Pharmacy, King Saud University Riyadh, Saudi Arabia.


477

Copyright 0 1990 by Academic Press, Inc. All rights of repduction in any form %%Ned

FARID I. MUHTADI AND MAHMOUD M. A. HASSAN

478

SCOPOLAMINE HY D ROBROM ID E

Contents 1. Description

1.1 1.2 1.3 1.4 1.5

Nomenclature Formulae Molecular Weight Elemental Composition Appearance, Color and Odor.

2. Physical Properties 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9

Melting Range E u t e c t i c Temperature S o l u b i l i t y Data pH Range S p e c i f i c Optical Rotation Dissociation Constant Crystal Structure X-Ray Powder D i f f r a c t i o n Spectral P r o p e r t i e s 2.9.1 2.9.2 2.9.3 2.9.4

U l t r a v i o l e t Spectrum Infrared Spectrum Nuclear Magnetic Resonance Spectra Mass Spectrum.

3. Isolation of Scopolamine

4. Synthesis of Scopolamine 4.1 P a r t i a l Synthesis 4 . 2 Total Synthesis 4.3 Synthesis o f Tropic Acid.

5. Biosynthesis of Scopolamine 6. Pharmacokinet ics

6.1 6.2 6.3 6.4 6.5

Drug Absorption Onset and Duration Distribution Excretion Metabolites.

SCOPOLAMINE HYDROBROMIDE

7. Pharmacology and Therapeutic Uses 8. Drug S t a b i l i t y and Storage

9. Methods of Analysis 9.1 9.2 9.3 9.4 9.5

Identification M i c r o c r y s t a l Tests T i t r i m e t r i c Determinations P o l a r o g r a p h i c Methods S p e c t r o p h o t o m e t r i c Methods 9.5.1 Colorimetric Determinations 9 . 5 . 2 UV Determinations 9 . 5 . 3 . I R Determinations 9 . 5 . 4 GC/Mass Methods

9.6

Chromatographic Methods 9.6.1 9.6.2 9.6.3 9.6.4

9.7

Paper Chromatography TLC Chromatography GLC Chromatography HPLC Chromatography

Radioligand Assay Methods

Acknowledgement References

479

FARID J. MUHTADI AND MAHMOUD M. A. HASSAN

480

1. Description 1.1

Nomenclature 1.1.1

Chemical Names a) a-(Hydroxymethyl) benzeneacetic acid 9methyl-3-oxa-9-azatricyclo [3.3.1.02,4] non-7-yl ester. b) 68, 78-epoxy-laHJ SaH-tropan-3a-01 (-) tropate. c) 68, 78-epoxy-3a-tropanyl S (-) -tropate. d) 6,7-epoxytropine tropate. e) Benzeneacetic acid, a- (hydroxymethyl)- , 9-methyl-3-oxa-9-azatricyclo r3.3.1 .O2,4] non-7-yl ester, [ 7 ( S ) -(la ,28,48,5a,78) 1. f) (-) - (1s,3s,5RJ6R,7s)-6,7-Epoxytropan-3yl ( s ) -tropate. Example for the hydrobromide salt: Benzeneacetic acid, a- (hydroxymethyl)- ,9methyl-3-oxa-9-azatricyclo [3.3.1.02J4] non-7-yl ester hydrobromide, [7(S)-(la,2B, 48,5aJ78)].

1.1.2

Generic Names Scopolamine hydrobromide; Hyoscine hydrobromide; Scopolammonium bromide; Scopolamine bromohydrate; Escopine tropate hydrobromide; Tropic acid ester with scopine as the hydrobromide.

1.1.3

Trade Names Transderm Scop (forl-scopolamine) Joy-rides; Quick K wells; Scopos; Sereen (for scopolamine hydrobromide)

.

1.2 Formulae 1.2.1

Empirical C17H21N04 C17H22Br NO4

1.2.2

Structural

(scopolamine) (scopolamine hydrobromide)

The structure of scopolamine has been confirmed by total synthesis, which was achieved


48 1

by several authors (1-4).

1 ' 0ll

CH2 OH I

0-c -CH

1.2.3

CAS Registry Number

[ 51-34 -31 Scopolamine [ 114-49-81 Scopolamine hydrobromide

1.2.4

Wiswesser Line Notation (5) TC 356 A AND OTJ A HOWR & 1 Q *DXLV(Scopolamine) TC 356 A AN D OTJ A HOWR & 1 Q & EH *DXLV (Scoplamine hydrobromide d l ) .

1.2.5

Stereochemistry The stereochemistry of scopolamine has been determined by chemical means as well as t h e X-ray crystalographic study of t h e hydrobromide s a l t ( 6 ) . I t i s established t h a t n a t u r a l (-)-scopolamine has t h e (S) -configurat i o n (by rezationship with (-)-t r o p i c acid

which has been shown t o possess t h e (S)configuration) ( 7 ) . The s t r u c t u r e o f (-) - (S) -scopolamine hydrobromide revealed t h e conformation of t h e t r o p i n e residue t o be as expected, with t h e


482

six-membered r i n g i n t h e c h a i r conformation. The epoxide oxygen atom on t h e methylene b r i d g e is i n t h e b o a t c o n f i g u r a t i o n with r e s p e c t t o t h e n i t r o g e n atom, and t h e methyl group C ( l ) a t t a c h e d t o t h e n i t r o g e n atom i s i n t h e a x i a Z p o s i t i o n with r e s p e c t t o t h e s i x membered r i n g (unZike the equatoriai! configura-

t i o n of t h i s methyi! group as found in cocaine hydrochloride ( 8 ), tropine ( 9 ) and pseudotropine ( 10) The e s t e r group a t t a c h e d t o C(13) i s i n t h e

.

a x i a l (a) p o s i t i o n o f t h e six-membered r i n g .

The structure o f (-1 - (S) -scopoZamine hydrobromide i s shorn i n F i g . 1 ( 6 ) .

0Y O I

Fig. 1 : The s t r u c t u r e of ( - ) - ( S ) scopolamine hydrobromide. 1.3

Molecular Weight 303.35 384.30

(Scopolamine) (Scopolamine hydrobromide)

483


1.4 Elemental Composition C, 67.31%; H, 6.98%; N, 4.62%; 0 , 21.10% (Scopolamine). 53.13%; H, 5.77%; Br, 20.80%; N, 3.65%; 0 , 16.65% (Scopolamine hydrobromide).

C,

1.5 Appearance, Color and Odor

- Scopolamine occurs as a viscous liquid, colorless,

-

2.

odorless. It forms a crystalline monohydrate (11). Scopolamine hydrobromide occurs a rhmobic crystals o r as a white crystalline powder, slightly efforescent in dry air ( 12 ,13 ) , odorless and has a very bitter taste (13).

Physical Properties 2.1 Melting Range 59' scopolamine monohydrate (11) . The following melting range has been reported for scopolamine hydrobromide: Melting Range Reference 197-200' (after drying at 105') Between 195-199" (after drying at 105") At about 197' (with decomposition) 195' 193-194' 2.2

(13) (14) (12) (11) (15)

Eutectic Temperature The eutectic temperature of scopolamine hydrobromide is recorded as follows ( 13 ) : Microscope Hot Stage Sal. Dic. -

Sal. 2.3

165' 126'

Hot Bar 168' 130'

~

=

Acetaminosalol; Dic. = Dicyandiamide

Solubility Data -

Soluble in 9.5 parts of water at 1S0, freely soluble in hot water, in alcohol, ether, chloroform, acetone. Sparingly soluble in benzene and petroleum ether (scopolamine) ( 11 ) .

FARID J. MUHTADI AND MAHMOUD M.A. HASSAN

484

-

2.4

One gram dissolves i n 1.5 water, 20 m l alcohol. S l i g h t l y soluble i n chloroform and almost i n s o l u b l e i n e t h e r (scopolamine hydrobromide) (11). The B.P. ( 1 2 ) reported t h e following s o l u b i l i t y data f o r scopolamine hydrobromide: soluble i n 3.5 p a r t s of water and i n 30 p a r t s of ethanol (96%); p r a c t i c a l l y insoluble i n chloroform and i n e t h e r .

pH Range Between 4.0 and 5.5. i n a s o l u t i o n (1 i n 20) (12,13),

2.5

S p e c i f i c Optical Rotation Scopolamine [a]D20

-

28'

(C=2.7)

(11)

[a]D - 18' (EtOH) Scopolamine hydrobromide: [,ID2'

- 24' t o

[a1 D

-

[.ID 2.6

24' to 25.9'

-

(15)

26'

(C=5) (11,14)

27'

(12)

(H20); [a]D

-

15.72'

(EtOH) (15)

Dissociation Constant pKa = 7.6 (23") scopolamine hydrobromide (16).

2.7

Crystal Structure The c r y s t a l s t r u c t u r e of (-) - ( S ) -scopolamine hydrobromide as Cl7HZ1NO4, HBr i s reported ( 6 ) . The

~2

c r y s t a l s a r e c o l o r l e s s needles, elongated along C , Lane group ~ 4 / m m m , space group - P ~ Z ~ Z ~ Z , a= 1196.5+0.7, c=2652?2 pm, Z=8. One h a l f molecule of water per molecule of scopolamine has been found crystallographically ( 6 ) . The d i s t a n c e s of t h e nitrogen atom from t h e various atoms of t h e molecule a r e : N-O(1) 247; N-O(2) 388, N-O(3) 541 and N-O(4) 804 pm. The molecule of (-) (S)-scopolamine hydrobromide projected down i s shown i n Fig. 1.

-

2.8

X-Ray Powder Diffraction The X-ray d i f f r a c t i o n p a t t e r n of scopolamine hydrobromide was determined with a P h i l i p s X-ray d i f f r a c t i o n sDectroeoniometer eauimed with PW 1730 generator. Y

L

-I

I

Y


485

R a d i a t i o n was p r o v i d e d by a copper t a r g e t (Cu anode W, High i n t e n s i t y X-ray t u b e o p e r a t e d a t 40 KV and 35 MV was used. The monochromator was a curved s i n g l e c r y s t a l (PW 1752). Divergance s l i t and t h e r e c e i v i n g s l i t were 0 and 0.1' r e s p e c t i v e l y . The s c a n n i n g speed of t h e goniometer used was 0.02 2 0 p e r second. The X-ray p a t t e r n o f scopolamine H B r is p r e s e n t e d i n F i g . 2 . Interplanner d i s t a n c e and r e l a t i v e i n t e n s i t y are shown i n t a b l e 1. y= 1.5480 A')

.

T a b l e 1 : X-Ray Powder D i f f r a c t i o n P a t t e r n o f Scopolamine Hydrobromide

11.45 9.57 7.73 6.99 6.16 5.81 5.29 5.01 4.76 4.51 4.31 4.18 4.14 3.99 3.88 3.62 3.58 3.45 3.38 3.30 3.15 3.12

92.9 13.8 16.7 9.8 36.1 61.9 74.9 17.4 100 49.9 63.1 55.0 43.0 55.5 10.5 24.1 54.4 36.0 17.0 30.8 50.6 24.9

3.04 2.98 2.91 2.86 2.76 2.66 2.59 2.52 2.47 2.37 2.33 2.27 2.20 2.13 2.07 2.03 2.01 1.99 1.78

11.8 27.4 11.2 11.0 36.5 21.6 20.0 13.9 21.2 22.4 12.4 16.9 10.0 10.6 10.1 10.0 12.8 11.4 10.3

d = i n t e r p l a n n e r d i s t a n c e , 1/10 = r e l a t i v e i n t e n s i t y (based on t h e h i g h e s t i n t e n s i t y of 1 0 0 ) .


Fig. 2 : X-Ray Diffraction Pattern of Scopolamine Hydrobromide.


2.9

481

Spectral Properties

2.9.1

U l t r a v i o l e t Spectrum (UV) The UV absorbance spectrum o f scopolamine hydrobromide i n methanol was scanned from 200 t o 400 nm u s i n g a Pye-Unicum SP 8-100 spectrophotometer (Fig. 3). Scopolamine hydrobromide e x h i b i t e d t h e f o l l o w i n g absorpt i v i t y v a l u e s (Table 2). Table 2 : UV a b s o r p t i v i t y v a l u e s max nm

246 252 258 264

A(1%, 1Cm)

E

134.5 153.7 172.9 115.3

3.5 4.0 4.5 3.0

Other r e p o r t e d W d a t a f o r scopolamine and salts:Substance Scopolamine

Solvent

0.1N H2S04

251 (El%, lcm 12) 257 ( 263.5 (

Scopolamine hydrochloride

Scopolamine

water

aqueous

N-butylbromide a c i d

2.9.2

Ref.

max nm

247 252 258 265 252

( ( ( (

I'

I'

I'

I'

'I

I'

I' I'

1

I'

"

(17 )

11.2)

'I

(A1 3.7)

258 ( 264 (

14)}

4.6) 3.6)

:;}

( 17 )

}

(16)

4) 3)

I n f r a r e d Spectrum (IR) The I R spectrum of scopolamine hydrobromide as K B r d i s c (1:200) was recorded on a P e r k i n E l m e r 580B I n f r a r e d spectrophotometer ( F i g . 4 ) . Assignment o f t h e f u n c t i o n a l groups have been c o r r e l a t e d with t h e following frequencies (Table 3).


488

i

240

300

4OOnm

Fig. 3 : UV Spectrum of Scopolamine HBr (MeOH)

0 1000

3500

3000

2500

2000

1800

1600

WOO

1200

1000

(Mo

Fig. 4 : 1R Spectrum o f Scopolamine Hydrobromide (KBr-Pellet).

600

100

2

490


Table 3 : I R C h a r a c t e r i s t i c s of Scopo 1amine Frequency Cm

-1

Functional groue

3350 (s) 2950 2810

OH (hydrogen bonded) CH ( s t r e t c h ) N-CH3

1728 (5) 1600 1166(s) , 1045 (s) 780 ,735,700 (s)

0-C-(ester) C=C (aromatic) C-0-C (ether) 5H (monosubstituted aromatics)

?

s = strong absorption The I R exhibited t h e following o t h e r absorption bands :1470, 1455, 1440, 1378(s), 1345, 1308, 1262, 1222(s), 1200, 1138(s) 1078, 1068, 1015, 980, 915, 858, 850, 610 cm- i

.

Clarke ( 1 7 ) reported t h e following p r i n c i p a l peaks f o r scopolamine: 1725, 1165, 1060, 1041 c m - l . For scopolamine hydrobromide i n K Br-disc t h e following p r i n c i p a l peaks were reported ( 16 ) : 1730, 1166, 1047, 853, 736 and 705 cm-l. 2.9.3

Nuclear Magnetic Resonance 2.9.3.1

‘H-NMR

Spectra

The proton s p e c t r a of scopolamine hydrobromide were recorded, once i n D20 on a Varian FT80A (80 MHz) NMR spectrophotometer (Fig. 5 ) , and another i n D20 using a Varian XL 200 (200 MHz) spectrophotometer (Fig. 6 ) using 4,4-dimethyl-4silapentane s u l f o n i c acid (DSS) as an i n t e r n a l reference with both. The proton chemical s h i f t s a r e assigned and shown i n t a b l e 4.

49 1


f l

t

'

1

'

1

'

1

'

1

'

1

'

1

'

1

.

I

.

I

'

1

'

1

'

1

'

1

1

1

'

,

'

I

'

I

'

I

I

I

I

,

Fig. 5 : 'H-NMR Spectrum of Scopolamine HBr (80 W z ) .

A+ , , ,., , , ,

1

1

,b t:lg,

(>

: 'H-NMII Spectrum

,

,

, , ,

,

, ,

6

of Scopolamine HBr (ZOO MHr).

, ,, ,

i

,

, , , I PPYO


492

0-c-cti9 Table 4: 'H-NMR Characteristics of Scopolamine Proton assignment 5 H aromatics (at

Chemical shifts 6 (ppm) 80 MHz 200 MHZ 7.41 (s) 7.42,7.47 (d)

c11,12,13,14,15) H at C3 HZOH at Cl0

5.05(t) 4.75 (s)

5.17(t) 4.81 (s)

H at Cg

4.07 (m)

4.02 (m)

H at C1 & H at C5

3.84(d)

3.88 (d)

H at C6 Fr H at C7

3.12 (d)

3.13(d)

2.84(s)

2.88 (s)

N-CH3 (C,) 2 H at C2 G 2H at

c4

1.9072.37 (m)

1.88-2.24 (m)

s = singlet, d = doublet, t = triplet, m = multiplet Other 1H-NMR data for scopolamine were also reported ( 18 - 2 0 ).

2.9.3.2

Carbon-13 NMR Spectrum The "C-NMR spectrum of scopolamine hydrobromide in D20 was recorded on a Varian XL-200 NMR spectrometer, using 4,4-dimethyl-4-silapentane sulfonic acid (DSS) as an internal reference. The spectrum is shown in Fig.7. The carbon chemical shifts were assigned and listed in table 5 .

493

SCOPOLAMINE HYDROBROMIDE 8

11

6

0

II

4 9

Table 5 : Carbon-13 Chemical S h i f t s of Scopolamine. Carbon Ass ignmen t

c9 C

12

‘13’

‘17

‘15 ‘14’

‘16

cll cl’ c5 ‘6’

‘7

clo c8 c29 c4

Chemical S h i f t 6 (PPm)

Multiplicity

172.96

Singlet

136.37

Singlet

129.89

Doublet

129.09

Doublet

128.90

Doublet

67.36

Doub 1e t

64.35

T r i p 1e t

62.88

Doublet

57.66 57.53

Doub 1e t

54.26

Doublet

31.18

Quartet

24.54 24.50

T r i p 1e t

Other ”C-NMR d a t a f o r scopolamine have been a l s o r e p o r t e d (21-23).


494

F i g . 7 : Carbon-13 NMR Spectrum of Scopolamine HBr.

IW.

w.

Fig. 8 : Mass Spectrum of Scopolamine.


2.9.4

495

Mass Spectrum The e l e c t r o n - i m p a c t i o n i z a t i o n ( E I ) mass spectrum o f scopolamine H B r i s p r e s c n t c d i n Fig. 8. Thc spcctrum was o b t a i n e d u s i n g a Finnigan MAT 5100 s e r i c s GC/MS s p c c t r o m e t e r o p c r a t i n g w i t h an i o n i z a t i o n p o t e n t i a l of 70 cV. The spcctrum e x h i b i t e d a m o l e c u l a r i o n peak a t a mass/charge (m/z) r a t i o o f 303.2 w i t h r e l a t i v e i n t e n s i t y of 6.4% and a b a s e peak a t m/z r a t i o of 94.1. The most prominent i o n s , t h e i r r e l a t i v e i n t c n s i t i e s as w c l l as some proposed i o n fragments are shown i n t a b l e 6. T a b l e 6 : Mass Fragments o f Scopolaminc

m/ z

-

Relative % Intensity

Ions

303

6.4

185

5.1

154

27.9

139

6.4

138

62.0

[ 139-HI

137

15.2

[138-H]

136

29.8

[ 137-HI

121

10.8

120

12.7

110

13.3

M+

-

-

[ 121-HI


496

Ions

-


109

11.4

[ 110-HI

108

44.3

[ 109-H]

103

20.3

98

28.5

-

97

11.4

[ 98-HI

m/

-

H2c I’ +

r 96

14.6

F 3

L

94

100

91

17.7

83

11.4

A!. +

82

17.1

81

25.3

79

13.3

[ 82 -HI

-


m/ z

-

497


Ions

77

19.0

71

8.9

-

70

15.8

[71-HI

69

15.8

[ 70-HI

68

15.8

[69-HI

67

15.8

[68-HI

65

9.5

57

28.5

56

11.4

55

24.0

44

24.0

-

43

23.4

[44-HI

42

63.3

[CH~=N=CH~]

41

36. '1

[42-HI

40

44.3

[41-HI

+

[57-HI

[CH. =N=CH

2

- CH2] +

Other mass s p e c t r a l d a t a of scopolamine have been r e p o r t e d ( 2 4 - 2 7 ) . The chemical i o n i z a t i o n (CI) mass s p e c t r a of scopolamine have been r e p o r t e d ( 25, 27 ) . Scopolamine e x h i b i t e d t h e following prominent i o n s w i t h t h e i r relative intensities. m/ z

-

Relative % In t ens it y

Ions

304

(4)

M*H+

306

(21)

-

138

(100)

156

(6 1

base peak

-


498

3.

I s o l a t i o n of Scopolamine Scopolamine occurs along with hyoscyamine and/or atropine i n several Solanaceous p l a n t s , such as species of Atropa, Datura, Hyoscyamu~, Duboisia, Mandragora and ScopoZia ( 2 8 ) , In some of t h e s e p l a n t s (Atropa and SeopoZia), hyoscyamine is t h e dominant a l k a l o i d throughout t h e l i f e c y c l e of t h e p l a n t . In Datura stramoniwn, hyoscyamine i s t h e p r i n c i p a l a l k a l o i d a t t h e time of flowering and a f t e r . Whereas young p l a n t s contain p r i n c i p a l l y scopolamine. In many o t h e r s p e c i e s o f Datura (e.g. D.ferox; D. metel; D. meteZoidGs), scopolamine i s t h e p r i n c i p l e alkaloid of t h e leaves a t a l l times ( 2 8 ) and t h e s e species a r e used t o i s o l a t e scopolamine. One o f the methods f o r t h e i s o l a t i o n of scopolamine i s described as follows ( 2 9 ) : The powdered Datura species i s throughly moistened with an aqueous s o l u t i o n of sodium carbonate and extracted with e t h e r o r benzene. The a l k a l o i d a l bases are e x t r a c t e d from the solvent with d i l u t e a c e t i c acid, t h e acid solut i o n is then shaken with e t h e r a s long a s t h e l a t t e r t a k e s up coloring matters. The a l k a l o i d s a r e p r e c i p i t a t e d with sodium carbonate, f i l t e r e d o f f , washed and dried. The d r i e d p r e c i p i t a t e i s dissolved i n e t h e r o r acetone, t h e s o l u t i o n i s dehydrated with anhydrous sodium s u l f a t e and f i l t e r e d . The f i l t r a t e i s concentrated, cooled when crude hyoscyamine and a t r o p i n e c r y s t a l i z e from s o l u t i o n , The c r y s t a l s a r e c o l l e c t e d by f i l t r a t i o n and t o t h e mother liquor d i l u t e hydrobromic acid i s added t o give scopolamine hydrobromide as c r y s t a l s , which i s c o l l e c t e d , washed, d r i e d and r e c r y s t a l l i z e d t o give pure c r y s t a l s .

4.

Synthesis of Scopolamine 4.1

P a r t i a l Synthesis

Since scopolamine i s an e s t e r of t h e aminoalcohol

scopine and t r o p i c acid, i t can t h e r e f o r e be obtained by heating scopine with t r o p i c acid i n t h e presence of hydrogen c h l o r i d e a s t h e same manner of a t r o p i n e (30). The e s t e r i f i c a t i o n can be a l s o performed by t r e a t i n g scopine hydrochloride with acetyltropoyl chloride i n nitrobenzene (1).


499

4.2 Total Synthesis SeveraZ schemes for the totaZ synthesis of scopolamine have been reported. Fodor e t a1 i n 1956 (1) has accomplished the f i r s t t o t a l synthesis o f t h i s a Zkaloid. Scheme I : Fodor's first total synthesis: Acetyltropenol is an important intermediate in this synthesis, it can be obtained by two alternative routes (31): 1) From ( 2 ) 3a, 68-dihydroxytropane [l] which is dehydrated to give 3a, 6a-oxidotropane [2], and this on acetobromolysis gives rise to 3a-acetoxy-68-bromotropane [3]. Dehydrobromination of [3] affords acetyl -6-tropene-3a-01 [4], which on hydrogenation gives acetyltropan-3a 01. 2) By starting with 6-hydroxytropan-3 one phenylurethane [ 51 which undergoes catalytic hydrogenation over Raney nickel to produce tropan-3a,6B-diol monophenylurethane [6]. This could be acylated easily either with acetyl chloride or with isovaleryl chloride. Distillation in a vacuum of these mixed esters proved sufficient to afford cleavage of the phenylcarbamyl group into phenyl isocyanate and the corresponding 3a-acetoxy68-hydroxytropane [7]. The latter gives with p toluene sulfonyl chloride the tosyl-ester [8], which undergoes, in turn, elimination on action of collidine o r triethylamine, affording acetyl-6-tropene-3a -01 [4]. [4] is subjected to oxidation with trifluoroperacetic acid thus producing acetylscopine [9]. Hydrolysis of [9] with N NaOH in acetone leads to scopine [lo], the hydrochloride of which is acylated, in turn, with acetyltropoyl chloride in nitrobenzene to furnish scopolamine [ll] besides a number of by-products. Separation of these can be achieved on a cellulose powder chromatogram and using butanol-N HC1 as the eluting solvent, pure scopolamine is resulted (identical with the natural product). T h i s f i r s t totaZ synthesis i s presented in scheme I [after 311. An improved and simpZified t o t a l synthesis of (-1-scopoZamine has been accompZished ( 2 1, t h i s c o n s t i t u t e s the second totaZ synthesis of scopolamine:Methoxysuccindialdehyde [2] after liberation from 2,3, 5-trimethoxytetrahydrofuran [ 11 (available from furan) is condensed with methylamine and acetone dicarboxylic acid to give 6-methoxytropinone [3]. This is reduced


500

Scheme I : The First Total Synthesis of Scopolamine ,!Ha

,CHI

N

N POC15

HO

?3

HO

[21

,CHI

h

B?.. CHa

N

*collidine or N(Ef)a

OAc

OAc

[41

[31

The a l t e r n a t i v e r o u t e for [4]

JHJ

CHI

1 , CHI

+ - +$o - o . ' " Ni/?H

Ph-N H-CO-0 H-CO

& rsi 151

/Ph

H

0

OH

[61

-

h

Ph-N H CO- 0

OAe

501


[41

OAC

502

FARID J. MUHTADI AND MAHMOUD M. A. H A S S A N

to 6-methoxytropan-3a-01 [4] which is de-0-methylated with aqueous hydrobromic acid to afford (t) -tropan-3a, 68-diol [5]. Internal cyclization with p-toluenesulfonic acid anhydride gives 3a, 6a-oxidotropane [6]. [6] upon cleavage with acetylbromide (acetobromolysis) gives 68-bromo-3a-acetoxytropane [7]. Piperidine is used to eliminate hydrogen bromide and the ester exchanged in a two-step process to produce 6,7-dehydrohyoscyamine [8]. Epoxidation of the hydrobromide of [8] with 30% hydrogen peroxide in the presence of sodium tungstate as catalyst leads to scopolamine hydrobromide [ 91 This improved totaZ synthesis i s presented i n scheme II [after ( 2 ) ] . A further modification of the totaZ synthesis of scopolamine has been reported 3 ) though t h i s modification depends on the same principles of the previous two syntheses:2,5-Diethoxy-2,5-dihydropyran [I] (made by anodic oxidation of furan in ethanol) is converted to its bromohydrin [I13 and this on basic hydrogenolysis yields 2,5-diethoxy-3-hydroxytetrahydropyran [III]. Mild acid hydrolysis of [111] leads to malic dialdehyde [IV] which undergoes Robinson-Schopf condensation to produce (f)-6-hydroxytropinone [V]. Treatment of [V] with phenylisocyanate leads to a urethane derivative capable of catalytic reduction to tropan -3a,68-diol monophenylurethane [VI] Acylation of the latter, followed by distillation results in cleavage of the phenylcarbamyl moiety to phenylisocyanate and the formation of 3a-acetoxy 68-hydroxytropane [VII]. This is converted into its corresponding tosyl ester with p-toluenesulfonyl chloride, elemination of toluenesulfonic acid could be induced with triethylamine to generate acetyl-6-tropene 3a-01 [VIII]. Epoxidation of the trifluoroacetate salt of [VIII] with trifluoroperacetic acid leads to acetylscopine [IX], this upon gentle basic hydrolysis (N NaOH in acetone) affords scopine [XI. Treatment of [XI with (t) -acetyltropoyl chloride followed by hydrolysis with dilute hydrochloric acid produces (+>scopolamine [XI]. Resolution of [XI] with (+)tartaric acid leads to (-)-scopolamine. This modified totaZ synthesis of scopoZamine is show i n scheme III.

.

.

503


Scheme 11 : The Second Total Synthesis of Scopolamine

X

7

I

2

n

N

4

Y

0

br

v

X

7

z

Y

X

-It

n

cn

Y

x


504

Scheme 111: Modified T o t a l Synthesis of Scopolamine

OOE t

o

h O E t Y [I11 O

T

h

&+n 1 N-CH3

0

0

[I V I

[VI

H\ /N '6'5

t

i

[I1

HO

[I111 E

O

-

1

H-y" . l O

H

OH

I

[VI 1

~

J[vlll

6'.*-

0

/H o OAC

H ~

OUC

OAC

11x1

[VIII]

___it

H

~H

HO

~

[XI H-

$

---

CH20H

[XI1

'gH5


505

A d i f f e r e n t approach t o the synthesis of scopine and hence t o scopoZamine has been recentZy reported ( 4 I: When a m i x t u r e o f tetrabromoacetone [ I ] , l - c a r b o methoxypyrrole [11] and d i i r o n e n n e a ( 3 : l : l . S mol r a t i o n ) i n benzene i s h e a t e d a t SO" f o r 72 hours under n i t r o g e n atmosphere, a m i x t u r e o f t h e dibromotropenone a d d u c t s [ I I I a , I I I b ] i n a 2 : l r a t i o i s o b t a i n e d . Zinc-copper r e d u c t i o n o f t h e adducts i n methanol c o n t a i n i n g 5% ammonium c h l o r i d e a t 25O f o r 10 minutes, a f f o r d s t h e tropenone adduct [ I V ] . Reduct i o n of [ I V ] with diisobutylaluminum h y d r i d e (DIBAH) f o r 2 3 hours a t -78O then f o r 8 hours a t 25' g i v e s r i s e t o t h e a l c o h o l s [Va and Vb]. These can b e p u r i f i e d by chromatographic column and c o n v e r t e d t o s c o p i n e [ V I ] and t h e n i n t o scopolamine.

This newer approach i s presented in scheme IV.

4.3

S y n t h e s i s of Tropic a c i d S e v e r a l schemes f o r t h e t o t a l s y n t h e s i s o f t r o p i c a c i d are known (Scheme I t o I V ) . Scheme I : Landenburg's s y n t h e s i s ( 32 ) . Acetophenone [ l ] i s c o n v e r t e d i n t o a, a - d i c h l o r o e t h y l benzene [2] by t h e a c t i o n o f phosphorous p e n t a c h l o r i d e . [ 2 ] i s r e a c t e d with potassium cyanide t o f u r n i s h a ethoxy-a-cyanoethylbenzene [ 3 ] . T h i s is hydrolysed w i t h barium hydroxide s o l u t i o n t o g i v e a t r o l a c t i c e t h y l e t h e r [ 4 ] . The l a t t e r i s heated w i t h hydrogen c h l o r i d e t o y i e l d a t r o p i c a c i d [ 5 ] which i s c o n v e r t e d t o t r o p i c a c i d [6]. Scheme 11: McKenzie and Wood's s y n t h e s i s ( 3 3 ) . Acetophenone [ l ] i s c o n v e r t e d by t h e a c t i o n o f p o t a s sium c y a n i d e t o acetophenone cyanohydrine [2]. This upon h y d r o l y s i s i s c o n v e r t e d i n t o a t r o l a c t i c a c i d [ 3 ] . The l a t t e r i s h e a t e d under p r e s s u r e t o y i e l d a t r o p i c a c i d [4]. A t r o p i c a c i d [ 4 ] i s t r e a t e d w i t h hydrogen c h l o r i d e i n e t h e r e a l s o l u t i o n t o form B-chlorohydrat r o p i c a c i d [5]. This upon b o i l i n g w i t h aqueous sodium c a r b o n a t e i s changed t o t r o p i c a c i d [ 6 ] . Scheme 111: MGller's s y n t h e s i s ( 3 4 ) . Ethylphenyl a c e t a t e [ l ] is condensed w i t h e t h y l f o r m a t e t o g i v e e t h y l a-formyl a c e t a t e [ 2 ] . T h i s on r e d u c t i o n w i t h aluminium amalgam y i e l d s d l - t r o p i c e s t e r [3] which upon h y d r o l y s i s g i v e s t r o p i c a c i d [ 4 ] .


506

Scheme I V : Recent Synthesis of Scope h i n e

5;,

[IIIa]

B V r

0B

r 0 [IIIb]

b-

N-CH3

0

H

OH

507


Scheme I: Landenburg's synthesis

-

FH>COOH 0 ~ 2 ~ 5 HC1

141

[31

ac-z* @ CH-COOH

[51

[61

Scheme 11: McKenzie and Wood's synthesis

CH2C1

CH20H 1

508

FARID J. hWHTADI AND MAHMOUD M. A. HASSAN

Scheme III: M i 2 Zer's synthesis L'HO

CH20H

@H-COOEt

[41 Scheme I V :

i31 Chambon ' s synthesis

Br I

@CH-COOEXn

/

+ [I1

Z n Br CH-COOEt I __c. HCHO

[21

CI H 2 0 H

CH2OH


509

Scheme IV: Chambon's s y n t h e s i s ( 35 ) . Ethyl a-bromophenylacetate [ l ] i s t r e a t e d w i t h Zn t o g i v e ethyl-a-zincbromophenylacetate [ 2 ] which i s t r e a t e d with formic a c i d t o g i v e d l - t r o p i c e s t e r [3] which upon h y d r o l y s i s y i e l d s t r o p i c a c i d [ 4 ] .

Methods of synthesis of tropic acid are presented i n schemes I t o I V . 5.

B i o s y n t h e s i s o f Scopolamine E a r l y work with i s o t o p e s has e s t a b l i s h e d t h a t o r n i t h i n e ( o r one of t h e r e l a t e d aminoacids i . e . glutamic a c i d o r p r o l i n e ( 36 ) and a c e t a t e (37,38 ) are p r e c u r s o r s of t h e t r o p i n e moiety ( a s [2-l4CC] o r n i t h i n e ; [5-14C] p r o l i n e and [1-14C] a c e t a t e were a l l i n c o r p o r a t e d i n t o hyoscyamine i s o l a t e d from f e d p l a n t s ) . I t i s b e l i e v e d t h a t t h e i n c o r p o r a t i o n o f g l u t a m i c a c i d o r p r o l i n e is c o n s i d e r e d t o o c c u r v i a o r n i t h i n e ( 36 ) , and t h e a c e t a t e i s i n c o r p o r a t e d v i a a c e t o a c e t i c a c i d ( 36 ) , a s f e e d i n g with [ 1 , 3 - 1 4 C ] a c e t o a c e t a t e r e s u l t e d i n t h e i s o l a t i o n of r a d i o a c t i v e hyoscyamine. I t h a s been shown t h a t p u t r e s c i n e was i n c o r p o r a t e d i n t o hyoscyamine (39,40 ) however, it i s p r e d i c t e d t h a t c e r t a i n enzymes a r e c a p a b l e of c o n v e r t i n g p u t r e s c i n e i n t o N-methylp u t r e s c i n e which it i s an e s t a b l i s h e d p r e c u r s o r o f t r o p i n e (36). I t has a l s o been shown t h a t (+)-(2R) h y g r i n e s e r v e s a s a p r e c u r s o r of t h e t r o p a n e a l k a l o i d s o f Datura innoxiu ( 4 1 ) , t h i s i s t r u e as (211)-hygrine i s formed by an a t t a c k o f t h e a c e t o a c e t a t e on t h e p y r r o l i n i u m s a l t ( 36 ) a s it i s e v i d e n t from scheme I. Very r e c e n t l y i t has been r e p o r t e d t h a t t h e b i o s y n t h e t i c pathway between o r n i t h i n e and hyoscyamine must be d i f f e r e n t i n Datura and Hyoscyamus aZbus ( 42 ), i . e . t h e c o n v e r s i o n of o r n i t h i n e t o t h e 1-methyl-A'-pyrrolinium s a l t (a p r e c u r s o r o f hyoscyamine) can proceed by two p a t h ways, one o f which ( i n Datura) can n o t i n v o l v e f r e e p u t r e s cine. P h e n y l a l a n i n e i s t h e e s t a b l i s h e d p r e c u r s o r of t r o p i c a c i d . T r a c e r s t u d i e s have shown t h a t t h e s i d e c h a i n of t h e aminoacid undergoes i n t r a m o l e c u l a r rearrangement d u r i n g t h e conversion t o t r o p i c a c i d ( 43 ) , t h u s upon f e e d i n g L-phenyl- [2-I4C] a l a n i n e , r a d i o a c t i v e ( - ) - t r o p i c a c i d i s r e s u l t e d a s i t i s e v i d e n t from scheme I . E s t e r i f i c a t i o n of t r o p i c a c i d with t r o p i n e produces hyoscyamine.

The biosynthesis of hyoscyamine i s presented i n scheme I [ a f t e r ( 44 ) I .


510

[yk

S-Adenosylmcthione

N-Methylpyrrolinium ion

+-

EH,COOH [2-14C]-Acetate

1 ~.Phenyl-[Z.~~C].alanine Itranraminatiin

Tropina

Scheme I :The Biosynthesis of

(-)-Tropic Acid

(-)-Hyoscyamine


511

Scopolamine appears to be formed in the plants from hyoscyamine ( 45,46,47 ) . It is believed that hyoscyamine [l] is metabolized in the plant to 6-hydroxyscopolamine [2], and this is further metabolized into 6,7-dehydrohyoscyamine [5]. Epoxidation in vivo of [5] gives rise to scopolamine [6]. Leete however, suggested that the dehydration takes place by a two step mechanism. A phosphorylated 6-hydroxyhyoscyamine [3] could be attacked by a nucleophilic reagent (represented by the SH-group of an enzyme) to afford [4]. The double bond of [4] is then generated by a trans elimination to give [5]. The biosynthesis of scopolamive from hyoscyamine i s presented i n scheme 11 [ a f t e r Leete ( 36 ) I .

"Oq

NMe

H

q

H

,-*

H

0 Tropyl Hyoscyarninc

i

[ 11

6-Hydroxyhyoscyarn~nc

H

c--

0 Tropyl Scopolamine

q

------>

Enzyme -SH

0 Tropyl H

NMe

0

o

&$

[ 61

6,7--Dehydrohyoscyarninc

[31

[ 21

*---

qH

Enyme-SE

0 Tropyl H

0 Tropyl H

[ 51

Scheme I1 : Biosynthesis of scopolamine from hyoscyamine.

0 Tropyl

141


512

6.

Pharmacokine t i c s 6.1

Drug Absorption Scopolamine i s r a p i d l y absorbed from t h e g a s t r o i n t e s t i n a l t r a c t f o l l o w i n g o r a l doses o f t h e hydrobromide (17,48,49}.It a l s o e n t e r s t h e c i r c u l a t i o n when a p p l i e d l o c a l l y t o t h e mucosal s u r f a c e s of t h e body ( 4 8 ) . Only l i m i t e d a b s o r p t i o n o c c u r s from t h e i n t a c t s k i n (48). The q u a t e r n a r y d e r i v a t i v e s o f scopolamine, such as t h e N-butylbromide o r t h e methobromide are p o o r l y absorbed from the g a s t r o i n t e s t i n a l t r a c t (49 ) and do n o t r e a d i l y p a s s t h e blood-brain b a r r i e r (49). The t o t a l a b s o r p t i o n o f q u a t e r n a r y ammonium d e r i v a t i v e of t h e b e l l a d o n n a a l k a l o i d s , a f t e r an o r a l dose i s only 10 t o 20% (50,51).

6.2

Onset and Duration

-

6.3

Following i n s t i l l a t i o n o f 1 drop o f 0.5% s o l u t i o n , maximum m y d r i a s i s occurs w i t h i n 20 t o 30 minutes; m y d r i a s i s is observed f o r up t o 7 days ( 3 t o 7 days) c 48 1. Following s i n g l e IM d o s e s of 0.05 t o 0.4 mg scopolamine, peak d e c r e a s e s i n p u l s e r a t e were e v i d e n t a t 1 t o 2 hours; d e c r e a s e s i n p u l s e r a t e p e r s i s t e d f o r approximately 8 hours ( 5 2 ) . Following s i n g l e IM doses o f 0.05 t o 0.4 mg s c o p o l a mine, peak d e c r e a s e s i n s a l i v a flow were e v i d e n t a t 1 t o 2 hours; t h i s s a l i v a r y flow was reduced f o r approximately 8 hours (52 j . Distribution Scopolamine H B r i s bound t o plasma p r o t e i n s ( 17 ) . Following a s i n g l e o r a l dose e q u i v a l e n t t o 415 pg of scopolamine t o 10 s u b j e c t s , a mean peak plasma c o n c e n t r a t i o n o f 0.0003 ug/ml was a t t a i n e d i n 0.5 t o 1 hour, d e c r e a s i n g t o 50% o f t h e peak c o n c e n t r a t i o n i n 2 t o 4 hours ( 5 3 ) . Scopolamine c r o s s e s t h e b l o o d - b r a i n b a r r i e r and it h a s been s t a t e d t o c r o s s t h e p l a c e n t a (49). Excretion

6.4

-

Only about 1%o f an o r a l dose o f scopolamine i s e l i m i n a t e d as such (unchanged) i n t h e u r i n e (48).


513

-

'

6.5

I n r a b b i t s , 2% of an o r a l dose and 30% of an i n t r a venous (IV) dose a r e e x c r e t e d i n 3 days (17). - About 5% o f an o r a l dose i s e x c r e t e d i n t h e u r i n e a s unchanged drug (16). Urinary e x c r e t i o n o f scopolamine was determined u s i n g a radioligand binding assay i n 9 healthy subjects f o l l o w i n g a d m i n i s t r a t i o n o f approximately 450 pg o f t h e drug o v e r 64 hours v i a a t r a n s d e r m a l d e l i v e r y system. During t h e time o f medication and 48 hours t h e r e a f t e r , a mean t o t a l o f 156 p g o f scopolamine i s e x c r e t e d i n t h e u r i n e o f which 21% was unchanged drug and t h e remainder 79% metabolized mainly a s g l u c u r o n i d e a n d / o r s u l f a t e c o n j u g a t e s . Steady s t a t e u r i n a r y c o n c e n t r a t i o n s were achieved about 1 2 hours a f t e r a p p l y i n g t h e medication. C o n c e n t r a t i o n s i n plasma were below t h e d e t e c t a b l e level o f 1 . 2 ng p e r m l (49,54). - Following a subcutaneous i n j e c t i o n o f 190 mg of scopolamine N-butylbromide i n 3 d i v i d e d d o s e s o v e r 4 hours, t h e u r i n e c o l l e c t e d contained t h e equivalent o f 26 mg o f t h e drug (55). - Scopolamine i s e x c r e t e d i n minimal amounts i n b r e a s t milk ( i f a t a l l ) and t h e d r u g can be a d m i n i s t e r e d t o n u r s i n g mothers. I t does n o t s i g n i f i c a n t l y a f f e c t m i l k s e c r e t i o n (56). - About 90% o f an o r a l d o s e of scopolamine butylbromide i s e l i m i n a t e d i n t h e faeces and less t h a n 10% i s e x c r e t e d i n t h e u r i n e ( 16 ) . A f t e r I V a d m i n i s t r a t i o n o f t h i s s a l t , about 40% of t h e dose i s e x c r e t e d i n t h e u r i n e (16).

-

Metabolites A s scopolamine i s an e s t e r a l k a l o i d , it i s p o s s i b l e t h a t s m a l l amounts a r e hydrolysed i n t h e serum ( 57 ) g i v i n g r i s e t o tropic acid as well a s scopine o r

.

scopo1ine Scopolamine glucuronides and sulfates a r e r e p o r t e d t o be t h e main scopolamine m e t a b o l i t e s i n man (54, 5 7 ) , w h i l e scopolamine 9 I-glucuronide is t h e main metabol i t e i n t h e mouse (54, 5 7 ) . Other r e p o r t e d s c o p o l a mine m e t a b o l i t e s :- aposcopolamine; norscopo2amin.e;

norscopolamine-9 '-glucuronide and 6-hydroxy hyoscyamine ( 57, 58).

(-)

-


5 14

7.

Pharmacology and Therapeutic Uses

This section is written by Dr. Zaki (59). Scopolamine e x e r t s t h e following pharmacological e f f e c t s : Central : 1) Sedative and t r a n q u i l i z i n g e f f e c t s with euphoria, but i n e l d e r l y and females, i t leads t o confusion a n d e x c i t e ment 2) Amnestic a c t i o n : I t leads t o t w i l i g h t s l e e p with morphine i n analgesia during labor.

.

3) A n t i e p i l e p t i c a c t i o n i n grandma1 a c t i o n on c o r t i c a l centres.

epilepsy by

4) Antikinetic a c t i o n : t o control r e g i d i t y and tremors i n chorea and Parkinsonjsm t o block t h e c e n t r a l cholinergic system i n basal ganglia.

5) Hypnotic action by a f f e c t i n g t h e brain-stem arousal mechanism which reaches t h e c e r e b r a l cortex. 6)

trigger 7)

Anti-emetic a c t i o n : by i n h i b i t i n g t h e chemo-receptor zone of t h e vomiting c e n t r e i n t h e medulla. Central r e s p i r a t o r y c e n t r e stimulation.

Peripheral: 1) I t possesses parasympatholytic action similar t o atropine but f i v e times more powerful on exocrine s e c r e t i o n s e.g. lacrymal, s a l i v a r y , and bronchial a s well as on eye i n form of passive mydriasis, cycloplegia and increase i n t r a o c u l a r pressure. 2 ) On cardiovascular system: it produces vasodilat i o n o f t h e blush skin a r e a with s l i g h t lowering i n blood pressure and tachycardia by decreasing vagal t o n e on t h e heart. 3) On g a s t r o - i n t e s t i n a l t r a c t : it decreases tone and amplitude of m o t i l i t y with marked decrease i n s a l i v a r y s e c r e t i o n but less decrease i n g a s t r i c and pancreatic secretions.

Therapeutic uses: 1) Pre-anesthetic medication: t o produce sedation thus shortens s t a g e of induction and antagonizes t h e r e s p i r a t o r y depression o f morphine and o t h e r depressants. I t is a l s o more powerful on glandular s e c r e t i o n s eg. bronc h i a l and s a l i v a r y decreasing r e s p i r a t o r y complications. 2)

In motion sickness and Manier's a t t a c k s .


3) In l a b o r an a 1ges ia .

515

w i t h morphine t o induce t w i l i g h t s l e e p

4) In parkinsonism and chorea t o reduce d y s k i n e s i a and r e g i d i t y . 5) L o c a l l y as eye drops o r ointement t o produce mydriasis and c y c l o p l e g i a i n c o r n e a l and i r i s l e s i o n s . I t i s less i r r i t a t i n g w i t h r a p i d recovery e s p e c i a l l y i n patients sensitive t o atropine.

Contraindicahions Scopolamine should n o t be a d m i n i s t e r e d t o p a t i e n t s with asthma, h e p a t i t i s , o r toxemia o f pregnancy ( 6 0 ) .

8. Drug S t a b i l i t y and S t o r a g e Scopolamine i s r e a d i l y racemized i n t h e p r e s e n c e o f d i l u t e a l k a l i (61). Scopolamine hydrobromide s o l u t i o n s a r e incompatible with a l k a l i s , s i l v e r s a l t s and t a n n i c a c i d . (49). Scopolamine hydrobromide as it is o r as t a b l e t s should be preserved i n t i g h t , l i g h t r e s i s t a n t c o n t a i n e r s (14). Scopolamine i n j e c t i o n s are preserved i n l i g h t r e s i s t a n t s i n g l e dose o r m u l t i p l e dose c o n t a i n e r s (14). Scopolamine hydrobromide ophthalmic s o l u t i o n s should b e s t o r e d i n t i g h t c o n t a i n e r s a t a temperature less t h a n 4OoC, p r e f e r a b l y between 15-3OoC, f r e e z i n g should b e avoided (14, 61). Scopolamine hydrobromide ointment is preserved i n c o l l a p s i b l e ophthalmic ointment t u b e s (14)

.

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9.

Methods o f Analysis 9.1

Identification

-

-

The following identification tests are mentioned in the British Pharmacopoeia ( 1 2 1 under hyoscine hydrobromide. To 1 mg add 0 . 2 m l o f fuming n i t r i c a c i d and e v a p o r a t e t o d r y n e s s on a water bath. Dissolve t h e r e s i d u e i n 2 m l of acetone and add 0.2 m l o f a 3% w/v s o l u t i o n of potassium hydroxide i n methanol; a v i o l e t c o l o r i s produced. Yields t h e r e a c t i o n s c h a r a c t e r i s t i c of a l k a l o i d s and t h e r e a c t i o n s c h a r a c t e r i s t i c of bromides.

1132e foZlowing tests are mentioned in the USP under scopolamine hydrobromide.

( 14 )

- Dissolve 3 mg i n 1 m l a l c o h o l , and e v a p o r a t e t h e

-

-

-

s o l u t i o n on a steam b a t h t o d r y n e s s . Dissolve t h e r e s i d u e i n 0.5 m l chloroform, add 200 mg of potassium bromide and 15 m l o f e t h e r , and s t i r f r e q u e n t l y d u r i n g 5 minutes. Decant t h e s o l v e n t , d r y t h e r e s i d u e on a steam b a t h u n t i l t h e odor of t h e s o l v e n t no longer i s p e r c e p t i b l e , and compress t h e r e s i d u e t o a d i s c . The i n f r a r e d a b s o r p t i o n spectrum o f t h e r e s u l t i n g p o t a s sium bromide d i s p e r s i o n , p r e v i o u s l y d r i e d a t 105' f o r 3 h o u r s , e x h i b i t s maxima only a t t h e same wavelengths a s t h a t of a similar p r e p a r a t i o n o f LISP Scopolamine Hydrobromide R.S., t r e a t e d i n t h e same manner. TO 1 m l o f a s o l u t i o n (1 i n 20) add a few drops o f c h l o r i n e TS, and shake t h e mixture with 1 m l c h l o r o form, t h e l a t t e r assumes a brownish c o l o r . Add t o scopolamine hydrobromide i n j e c t i o n s i l v e r n i t r a t e TS, a y e l l o w i s h w h i t e p r e c i p i t a t e i s formed, which i s i n s o l u b l e i n n i t r i c a c i d b u t s l i g h t l y s o l u b l e i n 6 N ammonium hydroxide.

Other identification tests are as fo2Zows:Gold c h l o r i d e t e s t ( 62 ) . To a few m l o f a 1%aqueous s o l u t i o n o f scopolamine hydrobromide a c i d i f i e d with h y d r o c h l o r i c a c i d , add a few drops of gold c h l o r i d e s o l u t i o n ; a lemon yellow o i l y p r e c i p i t a t e i s formed which c r y s t a l l i z e s a f t e r a while. The p r e c i p i t a t e i s t h e n r e c r y s t a l l i z e d from b o i l i n g water a c i d i f i e d with d i l u t e HC1 and d r i e d , scopolamine produces l u s t r o u s y e l l o w i s h broad p r i s m s ; m.p. 208-209'. Gerrard r e a c t i o n ( 6 3 ) . To a few mg o f t h e a l k a l o i d , a 2% v/w s o l u t i o n o f


517

mercuric c h l o r i d e i n 50% a l c o h o l , a w h i t e p r e c i p i t a t e i s produced.

-

Identification of scopolamine tablets: Digest a q u a n t i t y o f t h e f i n e l y powdered t a b l e t s e q u i v a l e n t t o about 0.005 g o f scopolamine hydrobromide w i t h 20 m l o f e t h a n o l (95%) f o r one h o u r , f i l t e r and e v a p o r a t e t h e f i l t r a t e t o d r y n e s s on a water-bath. D i s s o l v e t h e r e s i d u e i n 10 m l w a t e r , add 2 m l d i l u t e ammonia, and e x t r a c t with 3 q u a n t i t i e s each o f 5 m l o f e t h e r . F i l t e r t h e mixed e t h e r e a l e x t r a c t s i n t o a s m a l l g l a s s d i s h , and c a r e f u l l y evapor a t e t h e e t h e r on a water-bath. D i s s o l v e t h e r e s i d u e i n 1 m l 0.1 N H C 1 with t h e a i d of g e n t l e h e a t , add t o t h e s o l u t i o n 0.05 g potassium bromide and 0.5 m l o f gold c h l o r i d e s o l u t i o n (TS) A f t e r s e v e r a l hours draw o f f t h e l i q u i d and wash t h e c r y s t a l s of scopolamine auribromide with small q u a n t i t i e s o f w a t e r . Melting t e m p e r a t u r e o f t h e c r y s t a l s a f t e r d r y i n g o v e r phosphorous p e n t o x i d e i n vacuo f o r two hours about 192' ( 1 3 ) .

.

M i c r o c r y s t a1 Tests

9.2

A 0.1% w/v o f scopolamine H B r i n w a t e r was prepared

f o r t h e m i c r o c r y s t a l t e s t s . 1 t o 2 drops o f t h i s s o l u t i o n i s t r e a t e d on a m i c r o s c o p i c a l g l a s s s l i d e with equal drops o f t h e s p e c i f i c r e a g e n t , a f t e r a w h i l e t h e c r y s t a l s s o formed were m i c r o s c o p i c a l l y examined (64).

- K r a u t ' s r e a g e n t (modified potassium bismuth i o d i d e s o l u t i o n ) gave w i t h scopolamine a f t e r 5 minutes, r o s e t t e s o f p l a t e s (Fig. 9 ) .

-

Gold c h l o r i d e s o l u t i o n , f u r n i s h e d a f t e r 4 minutes curved p l a t e s (Fig. 1 0 ) . C l a r k e r e p o r t e d a s e n s i t i v i t y (1:1500) f o r t h e f i r s t t e s t , and (1:400) f o r t h e second t e s t (17). M i c r o c r y s t a l t e s t can be performed t o i d e n t i f y t r o p a n e a l k a l o i d s a f t e r e x t r a c t i o n from animal t i s s u e s (65) : These a l k a l o i d s a r e e x t r a c t e d from animal t i s s u e s with t h e u n i v e r s a l b u f f e r s o l u t i o n o r with a c i d s o l u t i o n a t pH 4.0 t o 5 . 0 ( o x a l i c o r t a r t a r i c a c i d ) . The a l k a loids a r e then i d e n t i f i e d microcrystallographically by r e a c t i o n with Rieneck's s a l t and by V i t a l i r e a c t i o n (65).

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Fig 9 :

Microcrystals of Scopolamine with Kraut’s Reagent.

Fig 10 :

Microcrystals of Scopolamine with Gold Chloride,


9.3

519

T i t r i m e t r i c Determinations 9.3.1

Aqueous T i t r a t i o n s Scopolamine H B r a s s a l t o r a s some of i t s f o r m u l a t i o n s can be assayed by a c i d - b a s e t i t r a t i o n ( 66 ) : The scopolamine b a s e i s e x t r a c t e d with c h l o r o form from ammonical s o l u t i o n . The combined chloroform e x t r a c t s i s washed , evaporated t o d r y n e s s and t i t r a t e d t o t h e end p o i n t with 0.05N a c i d ( s u l f u r i c a c i d o r HC1) u s i n g methyl r e d as an i n d i c a t o r 1 ml 0.05N acid = 0.02192g

of C17H2ZOqN, HBr, 3H20.

-

Determination o f s m a l l amounts o f n i t r o g e n o u s b a s e s ( i n c l u d i n g t r o p i n e a l k a l o i d s ) i n aqueous s o l u t i o n s such a s eye-drops and i n j e c t i o n s h a s been d e s c r i b e d (67). The method depends on p r e c i p i t a t i o n o f t h e a l k a l o i d w i t h t e t r a p h e n y l b o r o n a t pH 3 . 7 and t h e e x c e s s o f t h e r e a g e n t i s t h e n determined by b a c k - t i t r a t i o n with a s t a n d a r d s o l u t i o n o f q u a t e r n a r y ammonium s a l t t o a v i s u a l end p o i n t .

Melting points of t h e organic tetraphenylboron saZts may be used i n the i d e n t i f i c a t i o n of many of these compounds f66,67). Scopolamine butylbromide as well as o t h e r q u a t e r n a r y ammonium b a s e s o f t r o p a n e a l k a l o i d s can b e e s t i m a t e d by t i t r a t i o n a f t e r p a s s a g e o f t h e i r aqueous s o l u t i o n s through a s u i t a b l e i o n exchange r e s i n as f o l l o w s ( 68 ) : A weighed q u a n t i t y o f t h e sample i s d i s s o l v e d i n 10 m l o f w a t e r and p a s s e d through a r e s i n column packed with I R A 400 a t a r a t e o f 1 m l p e r minute. The column i s f i n a l l y washed w i t h water. 10 m l o f 0.1 N HC1 and 10 m l o f w a t e r are added t o t h e e l u a t e and t h e e x c e s s o f a c i d i s back t i t r a t e d withO.1NNaOH s o l u t i o n . 9.3.2

Non-aqueous t i t r a t i o n The USP (14) d e s c r i b e s a non-aqueous t i t r a t i o n method f o r t h e a s s a y o f scopolamine hydrobromide. D i s s o l v e about 750 mg o f scopolamine hydrobromide, a c c u r a t e l y weighed i n a m i x t u r e of 30 mL o f g l a c i a l a c e t i c a c i d and 10 mL of mercuric c h l o r i d e TS, warming s l i g h t l y t o

FARID J. MUHTADI AND MAHMOUD M.A . HASSAN

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*

e f f e c t s o l u t i o n , c o o l a t room temperature, add 2 drops o f c r y s t a l v i o l e t TS and t i t r a t e w i t h 0.1 N p e r c h l o r i c a c i d VS. Perform a blank d e t e r m i n a t i o n and make any n e c e s s a r y c o r r e c t i o n . Each 1 mZ o f 0.1 N perchZoric acid is equivalent t o 38.43 mg of C17H21N04. HBr.

The BP (12) recommends t h e f o l l o w i n g procedure: Dissolve 0.4 g o f scopolamine H B r ( o r 0 . 3 g scopolamine butylbromide) i n 20 m l o f anhydr o u s g l a c i a l a c e t i c a c i d , add 10 m l o f m e r c u r i c (11) a c e t a t e s o l u t i o n TS and l-naphtholbenzein s o l u t i o n as an i n d i c a t o r . T i t r a t e with 0.1 M p e r c h l o r i c a c i d VS, determining t h e end p o i n t potentiometrically. Each mZ o f 0.1 M perchloric acid VS is equivalent t o 0.03843 g of C17H21N04,HBr. or is equivalent t o 0.04404 g o f C21H30Br NO4 (Scopolamine buty lbromide)

.

Small amounts o f a l k a l o i d s (scopolamine H B r o r a t r o p i n e s u l f a t e ) i n i n j e c t i o n can b e e s t i m a t e d i n non-aqueous medium by u s i n g toZuene-p-sulfonic acid a s f o l l o w s (69). Aqueous s o l u t i o n (2 t o 5 m l , c o n t a i n i n g 2 t o 5 mg o f t h e a l k a l o i d ) i s t r e a t e d with sodium b i c a r b o n a t e t o pH 8 t o 9. The a l k a l o i d i s e x t r a c t e d with chloroform (15, 1 0 and 5 m l ) and t h e combined e x t r a c t s a r e f i l t e r e d through f i l t e r paper. The f i l t r a t e i s t i t r a t e d with 0.005 N toluene-p-sulfonic acid i n dioxan cont a i n i n g 1%phenol i n t h e presence o f dimethylyellow as an i n d i c a t o r . The method i s used f o r t h e d e t e r m i n a t i o n o f scopolamine hydrobromide ( o r a t r o p i n e s u l f a t e ) i n t h e presence o f morphine h y d r o c h l o r i d e :The sample i s made a l k a l i n e with NaOH s o l u t i o n t o pH 11 and scopolamine (or a t r o p i n e ) i s e x t r a c t e d with chloroform and determined as above. Many o t h e r t i t r i m e t r i c methods f o r t h e a s s a y of scopolamine have been p u b l i s h e d , some o f t h e s e a r e i n r e f e r e n c e s (70-74).


9.3.3

521

Potentiometric T i t r a t i o n s Scopolamine among o t h e r a l k a l o i d s i s e a s i l y t i t r a t e d i n aqueous s o l u t i o n s a t conc e n t r a t i o n s o f 0.01 t o 0.03M u s i n g t h e g l a s s e l e c t r o d e €or d i r e c t replacement r e a c t i o n s ( 7 5 ) . P o t e n t i o m e t r i c t i t r a t i o n may be c a r r i e d out by u s i n g a g l a s s e l e c t r o d e and a s t a n d a r d calomel c e l l a s r e f e r e n c e e l e c t r o d e (12). T i t r a t e with t h e t i t r a n t t o t h e c o l o r change o f t h e i n d i c a t o r t h a t corresponds t o t h e maximum v a l u e o f dE/dV (where E is t h e e l e c t r o motive and V t h e volume o f t i t r a n t ) . Hydrochlorides of s e v e r a l a l k a l o i d s and r e l a t e d s u b s t a n c e s i n c l u d i n g scopolamine were t i t r a t e d i n dimethyl s u l f o x i d e medium w i t h 0.1M AgNOj. End p o i n t s were determined by conductometric, p o t e n t i o m e t r i c and p o l a r i m e t r i c t e c h n i q u e s and t h e r e s u l t s were s a t i s f a c t o r y by t h e s e t h r e e techniques (76).

9.4

P o l a r o g r a p h i c Methods S e v e r a l a l k a l o i d s i n c l u d i n g scopolamine a s s a l t s (h ydrobromid e , hy droch 1o r i d e , n i t r a t e ) were d et ermi ned q u a l i t a t i v e l y and q u a n t i t a t i v e l y by t h i s method (77) * C o n c e n t r a t i o n s o f 0.001% ( o r lower) t o 1%o f a l k a l o i d s can be performed. A l k a l o i d s were q u a l i t a t i v e l y s e p a r a t e d a t t h e cathode o f an e l e c t r o l y t i c c e l l . O f t h e s e v e r a l k i n d s o f e l e c t r o d e s t e s t e d , aluminum a s anode (wrapped i n parchement) and a s t e e l one as cathode were most s a t i s f a c t o r y . The a l k a l o i d s c o l l e c t e d a t c a t h o d e were washed, d r i e d and t h e i r m e l t i n g p o i n t s were determined f o r i d e n t i f i c a t i o n . A d d i t i o n a l of NaCl t o t h e e l e c t r o l y z e d s o l u t i o n h a s t e n e d t h e s e p a r a t i o n o f a l k a l o i d s . Some a l k a l o i d s were q u a n t i t a t i v e l y determined. - O c i l l o p o l a r o g r a p h i c s t u d i e s of s e v e r a l a l k a l o i d s w i t h t r o p a n e and i s o q u i n o l i n e l i n k a g e s have been r e p o r t e d (77a). Various r e l a t e d a l k a l o i d s can b e d i s t i n g u i s h e d even i n m i x t u r e s by i d e n t a t i o n s i n t h e o s c i l l o g r a m s . Thus i t was p o s s i b l e t o d i s t i n g u i s h a t r o p i n e , hyoscyamine, scopolamine, homatropine H B r , c o c a i n e , h y d r a s t i n e , berberine a s well a s o t h e r a l k a l o i d s .


522

9.5

Spectrophotometric Methods 9.5.1

Colorimetric Determinations Morin (78 ) suggested t h e use of V i t a l i ' s r e a c t i o n f o r t h e determination of small amounts of atropine. Allport and Wilson (79 ) have a l s o adopted V i t a l i ' s reaction f o r t h e rapid determination of t h e a l k a l o i d s i n belladonna and stramonium. The method was found not applicable t o Hyoscyamus niger o r i t s g a l e n i c a l preparations (66 ) Allport and Jones (80 ) confirmed t h a t a t r o p i n e r e a c t s q u a n t i t a t i v e l y t h e same as hyoscyamine and t h e method i s a l s o applicable t o scopolamine. A s u m a r y o f t h i s determination can be described as follows :A q u a n t i t y of a l k a l o i d a l s o l u t i o n o r t a b l e t s containing between 1.6 t o 2 . 4 mg of atropine i s rendered a l k a l i n e and extracted with chloroform. The a l k a l o i d i s re-extracted from t h e chloroform with 6% a c e t i c acid and ethanol. An a l i q u o t of t h e r e s u l t i n g e x t r a c t is t r a n s f e r red i n t o an evaporating d i s h and evaporated j u s t t o dryness on a water bath, fuming n i t r i c a c i d (0.2 ml) i s immediately added t o t h e r e s i due and again evaporated t o dryness. The r e s u l t i n g residue i s dissolved i n acetone and made up t o volume (10 ml). A 3.0% potassium hydroxide i n methanol (0.1 ml) i s added and t h e mixture allowed t o stand f o r 5 minutes. A purple c o l o r i s developed and t h e i n t e n s i t y of t h i s c o l o r is then measured i n a photoe l e c t r i c absorptiometer. The concentration is c a l c u l a t e d from a c a l i b r a t i o n curve with q u a n t i t i e s of 0.025 mg t o 0.15 mg of pure hyoscyamine t r e a t e d s i m i l a r l y . A newer approach t o t h e v i t a l i type of r e a c t i o n has been reported by Freeman ( 8 1 ) : A measured q u a n t i t y of a l k a l o i d a l s o l u t i o n (containing about 0.05 t o 0.15 mg alkaloid) i s evaporated t o dryness on a water-bath, t h e residue i s n i t r a t e d with fuming n i t r i c a c i d ( 0 . 2 t o 0 . 3 m l ) and evaporated again t o dryness. The residue i s t r a n s f e r r e d t o a 10-ml graduated f l a s k with t h e a i d of small quantit i e s of dimethylformamide, 25% w/w aqueous

.

523


s o l u t i o n of tetramethylammonium hydroxide (0.3 ml) i s added t o t h e f l a s k which d i l u t e d t o volume with dimethylformamide. The r e s u l t i n g m i x t u r e i s allowed t o s t a n d f o r 5 minutes and t h e e x t i n c t i o n o f t h e developed c o l o r i s measured a t 540 wn i n 1-cm c e l l s a g a i n s t d i methylformamide. The a l k a l o i d a l c o n t e n t i s a s c e r t a i n e d from a c a l i b r a t i o n c u r v e which i s l i n e a r (66,81).

A m i x t u r e o f a t r o p i n e and scopolamine were q u a n t i t a t i v e l y s e p a r a t e d by e l e c t r o p h o r e sis and e s t i m a t e d by t h e same method ( 82 ) : Atropine and scopolamine were s e p a r a t e d w i t h 0.1 N aqueous ammonia as t h e e l e c t r o l y t e s . A f t e r e l u t i o n o f each a l k a l o i d , t h e e l u a t e was evaporated on a water-bath t o d r y n e s s and n i t r a t e d w i t h fuming n i t r i c a c i d , t h e r e s i d u e was d i s s o l v e d i n dimethylformamide and t r e a t e d as above. The e x t i n c t i o n (y) o f t h e produced c o l o r was measured a t 545nmand t h e c o n c e n t r a t i o n (X ug p e r ml) o f each a l k a l o i d was c a l c u l a t e d from t h e f o l l o w i n g e q u a t i o n : f o r atropine f o r scopolamine

X

= 113y + 0.8 X = 113y + 1 . 3

A c o l o r i m e t r i c method f o r t h e determinat i o n o f small amounts o f t r o p i c a c i d , mandelic a c i d and t h e i r e s t e r s ( a t r o p i n e , scopolamine and homatropine) h a s been r e p o r t e d ( 8 3 ) . Scopolamine i s n i t r a t e d f o r 15 minutes w i t h a s o l u t i o n o f 20% KNO3 i n c o n c e n t r a t e d H2SO4. On making t h e n i t r a t e d p r o d u c t a l k a l i n e w i t h h o t 18-20% NaOH, a c o l o r d e v e l o p s i n 30 minut e s . This c o l o r i s e s t i m a t e d by u s i n g an S42, S47 o r S5o f i l t e r i n t h e P u l f r i c h photometer. The s e n s i t i v i t y i s 50 and 60 pg of scopolamine p e r m l . The p r o b a b l e e r r o r is t3.0%.

C o l o r i m e t e r i c e s t i m a t i o n of a t r o p i n e and r e l a t e d a l k a l o i d s ( i n c l u d i n g scopolamine) i n pharmac e u t i c a l p r e p a r a t i o n s h a s been r e p o r t e d by two procedures ( 8 4 ) Procedure ( a ) : An a l i q u o t chloroform e x t r a c t p r e p a r e d by t h e USP method ( c o n t a i n i n g 0.25 t o 1.0 mg o f a l k a l o i d s ) was evaporated t o d r y n e s s on a w a t e r b a t h . Fuming n i t r i c a c i d (0.3) was added and h e a t e d t i l l fumes c e a s e d , t h e n t h e r e s i d u e was d r i e d a t 105' f o r 15 minutes and

.

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allowed t o c o o l , The r e s i d u e was d i s s o l v e d i n acetone and d i l u t e d t o 25 m l . An a l i q u o t ( 5 m l ) was mixed w i t h isopropylamine ( 2 ml) and 0.1% methanolic KOH (0.1 m l ) . The e x t i n c t i o n o f t h e produced c o l o r a t 540 nm was measured a f t e r one minute. Procedure f h l : The r e s i d u e was n i t r a t e d a s i n procedure ( a ) and d i s s o l v e d i n 50% e t h a n o l (10 ml). The e t h a n o l i c s o l u t i o n was heated on a water b a t h w i t h 10% HC1 ( 2 . 5 ml) and z i n c d u s t (0.1 g) f o r 10 minutes, cooled and f i l t e r e d . The zinc r e s i d u e was washed w i t h w a t e r and t h e washings were added t o t h e f i l t r a t e . 1%NaN02 ( 1 m l ) was added, mixed and allowed t o s t a n d f o r 10 minutes. 2.5% s o l u t i o n o f ammonium s u l f a m a t e ( 1 ml) was added, t h e m i x t u r e was shaked and allowed t o s t a n d f o r 10 minutes. 1%N-1-naphthylethyl-enediamine d i h y d r o c h l o r i d e s o l u t i o n (1 ml) was added and d i l u t e d t o 25 m l w i t h water. The e x t i n c t i o n of t h e produced c o l o r was measure a f t e r 30 minutes a t 550 run. The c o n c e n t r a t i o n was c a l c u l a t e d by r e f e r e n c e t o a s t a n d a r d curve. Recovery experiments i n both procedures i n d i c a t e d an accuracy o f ?l%. A photometric method f o r t h e q u a n t i t a t i v e d e t e r m i n a t i o n o f t r o p a n e a l k a l o i d s has been d e s c r i b e d (85). The d e t e r m i n a t i o n of scopolamine ( o r a t r o p i n e o r hyoscyamine) i s based on t h e r e a c t i o n o f t h e a l k a l o i d with p-dimethylaminobenzaldehyde r e a g e n t i n c o n c e n t r a t e d H2S04. The i n t e n s i t y o f t h e c o l o r s o produced being measured i n a p h o t o e l e c t r i c a b s o r p t i o m e t e r u s i n g a green filter. This method can be a p p l i e d f o r t h e microd e t e r m i n a t i o n o f scopolamine ( o r a t r o p i n e ) which r e q u i r e d s p e c i a l t r e a t m e n t , and measuring t h e e x t i n c t i o n a t 500 nm using a s u i t a b l e spectrophotometer ( 8 6 ) . A method f o r t h e d e t e r m i n a t i o n o f scopolamine hydrobromide o r a t r o p i n e b a s e has been r e p o r t e d ( 87 ) . In t h i s method, t h e a l k a l o i d i s p r e c i p i t a t e d with molybdophosphoric a c i d , t h e p r e c i p i t a t e can be d i s s o l v e d and reduced t o molybdium b l u e which can be c o l o r i m e t r i c a l l y measured. The following procedure was d e s c r i b e d : To 1 m l sample ( c o n t a i n i n g 0.2 t o 1 mg a l k a l o i d )


525

add 10% H2S04 ( 1 d r o p ) , 5% NH4Cl s o l u t i o n (0.2 ml) and 0.5% molybdophosphoric a c i d (dropwise 1 m l ) . After 10 minutes, f i l t e r t h e m i x t u r e , r e p e a t t h e f i l t r a t i o n , wash t h e p r e c i p i t a t e w i t h 0.15% H2SO4 (5x1 ml) and w i t h w a t e r (5x1 ml), d i s s o l v e t h e p r e c i p i t a t e i n a c e t o n e (2 m l ) , add e t h a n o l (2 ml) and 2 % a s c o r b i c a c i d s o l u t i o n (1 ml), set a s i d e f o r 15 m i n u t e s , add a c e t o n e (1 m l ) , c o o l t o 20' and d i l u t e with w a t e r t o 10 m l . Measure t h e e x t i n c t i o n a t 430 nm ( o r use an a p p r o p r i a t e f i l t e r ) a g a i n s t w a t e r i n 2 - m l c e l l s . Beer's law i s obeyedwith s t a t e d c o n c e n t r a t i o n s . The e r r o r i s 3.0% (87) N-butylscopolamine bromide a s w e l l a s o t h e r a l k a l o i d s can be assayed a s f o l l o w s

-

(88).

Scopolamine s a l t (< 0.5 mg) i s e x t r a c t e d from paper chromatography w i t h c i t r a t e - p h o s p h a t e b u f f e r s o l u t i o n (pH 7 . 5 ) (20 ml), 0.15% bromothymol b l u e s o l u t i o n ( 1 m l ) i s added and t h e mixture e x t r a c t e d with chloroform (3x20 ml). The combined chloroform e x t r a c t s a r e mixed w i t h 2 % e t h a n o l i c H3B03 (25 ml), f i l t e r e d and t h e r e s u l t i n g f i l t r a t e i s d i l u t e d t o 100 m l w i t h e t h a n o l . The e x t i n c t i o n i s measured a t 436 nm a g a i n s t a r e a g e n t blank i n 2-cm c e l l s . The reproducibility f. 2%. The c o l o r i m e t r i c r e a c t i o n o f T r o p a e o l i n 00 with a l k a l o i d s under a c i d i c c o n d i t i o n s i s used f o r m i c r o q u a n t i t a t i o n of a l k a l o i d s (Haussler 89). The aqueous s o l u t i o n o f an a l k a l o i d (5 ml) ( c o n t a i n i n g E 100 ug) i s mixed with a similar q u a n t i t y o f an a c e t i c b u f f e r (pH 4.6) and 3 m l o f a s a t u r a t e d aqueous T r o p a e o l i n 00. The r e s u l t i n g mixture i s t h e n e x t r a c t e d w i t h c h l o r o form (4x5 ml). The combined e x t r a c t s a r e a c i d i f i e d w i t h 2 m l o f an a c i d r e a g e n t ( 1 m l concent r a t e d H2SO4 and 99 m l methanol) and d i l u t e d t o 25 m l w i t h chloroform. The a l k a l o i d i s t h e n determined s p e c t r o p h o t o m e t r i c a l l y at 545 n m and c a l c u l a t e d from a s t a n d a r d curve ( 8 9 ) . The above method was a p p l i e d f o r t h e d e t e r m i n a t i o n of s m a l l amounts o f hyoscyamine and scopolamine i n crude drugs ( 9 0 ) : These a l k a l o i d s were f i r s t s e p a r a t e d by p a p e r

526


chromatography with t h e solvent n-butanolg l a c i a l a c e t i c acid ( l O : l ) , s a t u r a t e d with water. After development, t h e spots were eluted, t r e a t e d and determined as above. Tropane a l k a l o i d s including scopolamine can be determined c o l o r i m e t r i c a l l y as follows ( 91 ) : Alkaloidal s a l t (1 mg) i s dissolved i n water (100 ml). To an a l i q u o t of t h i s (1 ml), mM bromocresol purple (3 ml) and b u f f e r s o l u t i o n of pH 4 . 0 (2 ml) a r e added. The s o produced c o l o r i s extracted with chloroform (4x5 ml). The combined e x t r a c t s a r e d i l u t e d t o 10 m l with chloroform. The absorbance of t h i s a t t h e absorption maxima (405 to 410 nm) i s measured. The alkaloid cont e n t i s then c a l c u l a t e d from a c a l i b r a t i o n g r a p h . Hydrolysis products of a l k a l o i d s do not i n t e r f e r e unless present i n threefold amounts. The r e l a t i v e e r r o r of t h e method does not exceed 2 1%. The hydrobromide and methylbromide s a l t s o f scopolamine i n t a b l e t s can be assayed by t h e following method (92). Powdered t a b l e t s a r e extracted with water and s u i t a b l y d i l u t e d . To an a l i q u o t (5 m l :13 mg of a l k a l o i d ) i n 50 m l f l a s k placed i n an i c e water bath, s a t u r a t e d aqueous hydroxylammoniwn c h l o r i d e s o l u t i o n (1 ml) and 10.5 M KOH (1 ml) a r e added, mixed and set a s i d e f o r 1 hour. 4 M HC1 (2 ml) i s added t o t h e mixture t o give a pH range of 1 . 2 t o 1.4. 0.37 M FeC13 s o l u t i o n i n 0.1M HC1 ( 1 ml) i s then added and mixed. The f l a s k is removed from t h e bath, gas evolut i o n i s allbwed t o subside and t h e e x t i n c t i o n of t h e product i s then measured a t 540 nm against a blank. Other c o l o r i m e t r i c methods have a l s o been reported (93-99). 9.5.2

U l t r a v i o l e t Determinations A physical method is described f o r t h e determination of scopolamine H B r i n diphenhydramine-scopolamine t a b l e t s (100). 20 crushed t a b l e t s a r e shaked with 10 m l absol u t e ethanol f o r 5 minutes and centrifuged.


527

The s u p e r n a t a n t s o l u t i o n (8 ml) i s evaporated on a steam water b a t h u n t i l d r y n e s s , t h e r e s i due i s d r i e d o v e r n i g h t i n a vacuum. The d r i e d r e s i d u e is warmed a t 50' f o r 15 t o 20 minutes 1 m l o f NaC1-saturated d i e t h y l a c e t a m i d e and c e n t r i f u g e d . The r e s u l t i n g s o l u t i o n i s examined s p e c t r o s c o p i c a l l y i n t h e r e g i o n o f 11 t o 1 2 p using a solvent blank. An accuracy > 90% i s a t a i n e d and t h e method i s u n a f f e c t e d by a high p r o p o r t i o n o f diphenhydramine HC1. Systematic t o x i c o l o g i c a l a n a l y s i s by s p e c t r o p h o t o m e t r i c method h a s been published (101). The sample o f t i s s u e i s homogenized with 0.1N HC1 (25-ml). The homogenate-is e x t r a c t e d on a water b a t h with 95% e t h a n o l (75 ml) and 10% Na2W04 (2 m l ) . The r e s i d u e i s d i s s o l v e d i n MaIlvain's b u f f e r a t pH 7.0 and e x t r a c t e d with chloroform (50 ml) The s e p a r a t e d chloroform l a y e r is then e x t r a c t e d with 0.1N HC1 (100 ml). The c h a r a c t e r i s t i c UV a b s o r p t i o n curves f o r 30 a l k a l o i d s i n c l u d i n g scopolamine i n d i l u t e HC1 are p r e s e n t e d . Scopolamine hydrobromide a s well as a t r o p i n e s u l f a t e i n eye-drops, each can b e d e t e r mined by UV t e c h n i q u e ( 102 ) . Both a l k a l o i d s show maxima a t 186 nm. To determine scopolamine, d i l u t e 1 m l sample t o 1 I t . with w a t e r , 20 m l o f t h i s s o l u t i o n i s f u r t h e r d i l u t e d t o 100 m l with water. The e x t i n c t i o n a t 186 nm i s measured a g a i n s t w a t e r . B e e r ' s law i s obeyed o v e r t h e range o f 0 t o 6 pg o f scopolamine p e r m l . The r e s u l t s o b t a i n e d are w i t h i n 1%o f t h o s e o b t a i n e d by e x t r a c t i o n methods.

.

S e v e r a l a l k a l o i d s i n c l u d i n g scopolamine can be assayed i n aqueous s o l u t i o n s of t h e i r s a l t s p a r t i c u l a r l y ampoules by UV s p e c t r o photometric method ( 103 ) . The e x t i n c t i o n o f t h e d i l u t e d sample i s determined a t t h e wavelength f o r maximum a b s o r p t i o n (257 to 286 nm). Scopolamine i n scopolamine butylbromide

can be determined as f o l l o w s ( 1 0 4 ) . A s o l u t i o n o f t h e sample i n water ( 2 g i n 4 ml) i s t r e a t e d with aqueous ammonia ( 1 ml), s a t u r a t e d with sodium c h l o r i d e and e x t r a c t e d with a

FAEUD J . MUHTADI AND MAHMOUD M. A. HASSAN

528

mixture of chloroform-carbontetrachloride (1:2) (5 x 1 0 ml). The combined e x t r a c t s a r e d r i e d over anhydrous sodium s u l f a t e and evaporated t o dryness under reduced pressure. The residue i s extracted with carbon t e t r a c h l o r i d e (5 x 10 ml) and t h i s e x t r a c t i s again evaporated t o dryness under reduced pressure. The residue i s then dissolved i n ethanol ( 1 0 ml). An a l i q u o t of t h i s (1.5 ml) i s d i l u t e d with water ( t o 100 ml) and t h e e x t i n c t i o n o f t h e d i l u t e d s o l u t i o n i s measured a t 205 nm against 1.5% ethanol i n water. A standard s o l u t i o n i s prepared by subjecting scopolamine (10 mg) t o t h e same procedure. The recovery of scopolamine i s 96.5+1.63%, and t h e r e s u l t s agree with those obtained by GLC of t h e sample ( a f t e r t r i m e t h y l s i l a t i o n ) on a column of 1.5% of SE-30 on Chromosorb W at 220' using N as a c a r r i e r gas. Unit-dose assay o f tropine a l k a l o i d s can be performed by charge t r a n s f e r complex technique (105). Samples of powdered t a b l e t s , i n j e c t i o n solut i o n s , eye drops a r e extracted with 1 , 2 dichloroethane. A volume of t h e r e s u l t i n g e x t r a c t (containing 0.05 t o 0.15 mg of alkal o i d ) i s mixed with mM-iodine i n dichloroethane (1 ml). The mixture i s then d i l u t e d with d i chloroethane (10 ml). The e x t i n c t i o n of t h e charge t r a n s f e r complex i s measured a t t h e maximum of 280 nm o r a t 295 nm against a reagent blank. The c o e f f i c i e n t of v a r i a t i o n was 1.6 t o 2.8%. 9.5.3

I n f r a r e d Determinations The a p p l i c a t i o n of I R spectrophotometry t o t h e q u a n t i t a t i v e determinations of a t r o p i n e and scopolamine has been reported (106). The pressed K B r p e l l e t technique was applied i n t h e s e determinations. Recoveries from standard mixtures showed a mean value of 104% f o r a t r o pine and 98.2% f o r scopolamine. I R spectroscopy has been recommended f o r t h e i d e n t i f i c a t i o n of scopolamine (107). To obtain reproducible s p e c t r a and avoid polymorphic e f f e c t s , t h e following technique was performed.


529

An ammonical aqueous s o l u t i o n o f t h e t a b l e t s o r i n j e c t i o n s o f scopolamine was e x t r a c t e d w i t h chloroform and t h i s e x t r a c t was a p p l i e d t o a column o f C e l i t e impregnated w i t h NaBr and H3P04. The hydrobromide so formed was e l u t e d with w a t e r s a t u r a t e d chloroform. The e l u a t e was evaporated, t h e r e s i d u e was mixed w i t h K B r and compressed i n t o a d i s c f o r I R identification. 9.5.4

GLC-Mass S p e c t r o m e t r i c Determination A GLC-mass s p e c t r o m e t r i c method f o r submicrogram (50 pg/ml) a s s a y of scopolamine i n plasma and u r i n e h a s been developed (108). The method used a d e u t e r a t e d i n t e r n a l s t a n d a r d t o minimize v a r i a b i l i t y i n a b s o l u t e r e c o v e r y i n t h e e x t r a c t i o n procedure. S c o p o l i n e and d e u t e r a t e d s c o p o l i n e were formed from t h e b a s e - c a t a l y z e d h y d r o l y s i s of s c o p o l a mine and t h e i n t e r n a l s t a n d a r d and were a n a l y zed a s t h e h e p t a f l u o r o b u t y r a t e s , u s i n g a GLCmass s p e c t r o m e t r i c system by monitoring t h e m/e 138 and 1 4 1 fragments r e s p e c t i v e l y .

Procedure: A plasma o r u r i n e sample (2-4 ml) i s mixed

with (-)-N-trideuteroscopolamine as i n t e r n a l s t a n d a r d and t h e m i x t u r e is a d j u s t e d t o pH 9.75 with 1 M c a r b o n a t e b u f f e r (2 ml) and e x t r a c t e d with methylene c h l o r i d e . The e x t r a c t i s p u r i f i e d by s o l v e n t p a r t i t i o n , t h e n t h e a l k a l o i d s a r e hydrolyzed t o s c o p o l i n e and d e u t e r o s c o p o l i n e by h e a t i n g with 5N NaOH a t 50" f o r 30 minutes. The s u b s t a n c e s a r e f u r t h e r p u r i f i e d by s o l v e n t p a r t i t i o n and converted t o t h e i r heptafluorobutyryl derivat i v e s . The d e r i v a t i v e s a r e t h e n s u b m i t t e d i n t o t h e f o l l o w i n g GLC-mass system: S i l a n i z e d g l a s s column (1.8m x 2mm i . d . ) packed with 3% OV-17 ( f o r plasma samples) o r with 1% OV-225 ( f o r u r i n e samples) on Gas-Chrom Q (100-120 mesh), o p e r a t e d a t 95". The s i g n a l r a t i o s a t m/e 138 and 141 a r e measured. The procedure i s s e n s i t i v e t o 50 pg m l - 1 . The c o e f f i c i e n t o f v a r i a t i o n a t t h e l e v e l o f 250 pgm-l ( 5 d e t e r m i n a t i o n s on d i f f e r e n t days) was 2.5% (108).

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9.6 Chromatographic Methods

9.6.1

Paper Chromatography

Clarke ( 17 ) described the following three systems for the identification of scopolamine and derivatives:1)Whatman No. 1, sheet 14 x 6 inches, buffered by dipping in a 5% solution of sodium dihydrogen citrate, blotting and drying at 25' for one hour. It can be stored indefinitely. A solvent composed of 4.8 g of citric acid in a mixture of 130 ml of water and 870 ml of n-butanol was used (109). The following Rf values were reported: Scopolamine 0.23 Scopolamine butylbromide 0.93 Scopolamine methonitrate 0.20 Location reagent: Iodoplatinate spray. 1I)Whatman No. 1 or No.3,sheet 17 x 19 cm, impregnated by dipping in a 10% solution of tributyrin in acetone and drying in air. Solvent system: acetate buffer (pH 4.58). Equilibration: The solvent in a beaker was equilibrated in a thermostatically controlled oven at 95' for about 15 minutes (110). Rf value of scopolamine = 0.93. Location reagent: as for I. 1II)Chromatogram: as for 11. Solvent system:phosphate buffer (pH 7.40). Equilibration: The solvent in a beaker was equilibrated in a thermostatically controlled oven at 86' for about 15 minutes (111). Location reagent: as for I. Rf values: for scopolamine 0.57; for scopolamine methonitrate 0.93. Paper chromatography has been used for quantitative determinations of the tropane alkaloids or for their separation from crude drugs prior to determination. The following system was reported for the microdetermination of solanaceous alkaloids (112) Ethereal extract of a crude drug was applied to strips of filter paper impregnated with potassium chloride solution. The chromatograms were developed in the solvent n-butanol-aqueous


531

HC1 by t h e ascending t e c h n i q u e f o r 20 h o u r s . A f t e r development, t h e chromatograms were d r i e d , sprayed w i t h modified Dragendorff I s r e a g e n t and a r e a s o f t h e s p o t s were measured. The r e l a t i v e c o n c e n t r a t i o n s o f t h e i n d i v i d u a l a l k a l o i d s were c a l c u l a t e d by r e f e r e n c e t o c a l i b r a t i o n curves. R f v a l u e s : hyoscyamine 0.85; scopolamine 0.63 and a t r o p i n e 0.34 (112).

(-)-Scopolamine can be determined i n t h e p r e s e n c e o f excess morphine and ethylmorphine ( 113 ) . A f t e r s e p a r a t i o n o f t h e mixture on paper chromatograms, t h e s p o t s were measured by means o f a d e n s i t o m e t e r and t h e c o n s t r u c t e d curves evaluated planimetrically. Tropane a l k a l o i d s i n crude drugs can be q u a l i t a t i v e l y i d e n t i f i e d , s e p a r a t e d by p a p e r chromatography and q u a n t i t a t i v e l y assayed by colorimetric determination ( 114 ) Whatman no.3 f i l t e r paper was used and t h e chromatograms were developed with t h e s o l v e n t water s a t u r a t e d n - b u t a n o l - g l a c i a l a c e t i c a c i d (25 :1 ) f o r 18 hours. Corresponding a r e a s on t h e chromatograms were i d e n t i f i e d , c u t o f f , e l u t e d w i t h e t h a n o l and determined c o l o r i m e t r i c a l l y .

.

Other paper chromatographic systems have been r e p o r t e d (115-118). 9.6.2

Paper E l e c t r o p h o r e s i s Measurements o f t h e e l e c t r o p h o r e t i c m o b i l i t y of 68 d i f f e r e n t a l k a l o i d s i n c l u d i n g scopolamine were reported ( 119 ) This was performed i n an LKB a p p a r a t u s on Whatman no. 1 p a p e r (18 x 46 cm) a t 8v/cm f o r 3 hours i n t h e p r e s e n c e o f u n i v e r s a l b u f f e r s a t v a r i o u s pH v a l u e s . The r e l a t i v e d i s p l a c e m e n t s ( r d ) f o r s c o p o l a mine a t v a r i o u s pH v a l u e s were r e p o r t e d as follows: pH 2.3, 4.3, 6.4, 8.2, 10.5 and 11.4 r d 67, 66.5, 104, 60, 33 and 1 3 The a l k a l o i d s were i d e n t i f i e d i n f i l t e r e d UV o r by s p r a y i n g w i t h v a r i o u s a l k a l o i d a l r e a g e n t s .

.

9.6.3

Thin Layer Chromatography (TLC) Many TLC systems have been r e p o r t e d f o r t h e i d e n t i f i c a t i o n o f scopolamine and o t h e r t r o p a n e a l k a l o i d s . S e v e r a l o f t h e s e systems a r e p r e s e n ted i n table 7.


532

Table 7 : TLC o f Scopolamine

-

Solvent System

Zhromatogram ~~~

1.

Methano 1-strong ammonia Silica gel G (0.25 mm layers) (100: 1.5)

2.

Silica 250 pm iipped KOH i n

3.

4.

gel G thick, i n 0.1M methanol

Silica gel G layers I1

11

5. 6.

11

II

Rf 0.54

Chloroform-methanol (90: 10)

0.39

Chloroform-acetonediethyl-amine (5:4:1)

0.56

Chloroform-diethyl amine (9 :1)

0.6

Cyclohexane-chloroformdiethylamine (5 :4 :1)

0.19

Benzene - ethyl a c e t a t e diethylamine (7:2:1)

0.34

7.

Aluminium oxide G. layers

Chloroform

0.30

8.

Basic s i l i c a gel G.

Met hano 1

0.52

9.

Si l i ca gel G layers

E t hy 1a c e t a t e - e thano 1 dimethylformamidediethylamine (12:6:1 :1)

10

Alkaline s i l i c a gel G layer dipped i n 0.5N KOH

Ref.

~

-

70% Ethanol-25% ammonia (99 :1)

0.73 0.83

TLC h a s a l s o been used f o r q u a n t i t a t i v e determinations of t h e tropane a l k a l o i d s .

Belladonna a l k a l o i d s can be determined by q u a n t i t a t i v e TLC (123). Samples of Belladonna a r e extracted according t o t h e method o f Pharm. Helv. V (Swiss Pharmacopeia V ) . The a l k a l o i d s so extracted a r e then separat e d on k i e s e l g e l G p l a t e s with t h e solvent acetoneaqueous ammonia (19 :1 ) . After development , t h e chromatograms a r e d r i e d , sprayed with Dragendorff s reagent and t h e areas of t h e spots a r e measured.


533

The r e s u l t s o b t a i n e d by t h i s procedure a g r e e with t h o s e o b t a i n e d by t h e modified Pharm. Helv. V methods (123). Hyoscyamine and scopolamine can be d e t e r mined by d i r e c t photodensitometry on t h i n l a y e r chromatograms (124). After e x t r a c t i o n o f a l k a l o i d s from powdered hyoscyamus (4 g) and p u r i f i c a t i o n , an a l i q u o t i s a p p l i e d t o 0.5 mm l a y e r s o f s i l i c a g e l G which developed f o r I1 hour with t h e s o l v e n t h y d r o u s methanol-aqueous ammonia ( 2 0 0 : l ) . After development, t h e p l a t e s a r e d r i e d a t room t e m p e r a t u r e , sprayed with modified Dragendorff's r e a g e n t . The s p o t s a r e scanned a t 490 nm with a r e c o r d i n g and i n t e g r a t i n g densitometer. The i n t e g r a t o r count i s a r e c t i l i n e a r f u n c t i o n of t h e weight o f a l k a l o i d o v e r t h e range o f 4 t o 65 pg f o r hyoscyamine and 7 t o 60 pg f o r scopolamine. The r e s u l t s agreed well with t h o s e o b t a i n ed by t h e s p e c t r o p h o t o m e t r i c method o f Freeman (81)

-

Tropane a l k a l o i d s i n g a l e n i c a l p r e p a r a t i o n s (syrups, tablets, suppositories) can be d e t e r -

mined c o l o r i m e t r i c a l l y a f t e r s e p a r a t i o n on TLC p l a t e s (125). The a l k a l o i d s are e x t r a c t e d w i t h ammonical e t h y l ether-chloroform mixture. The o r g a n i c l a y e r o f t h e e x t r a c t i s evaporated and d i s s o l v e d i n e t h a n o l . This i s a p p l i e d i n t o t h i n l a y e r s o f s i l i c a g e l GF254 which developed i n t h e s o l v e n t e t h a n o l w a t e r - t r i e t h a n o l a m i n e (5:4: 1 ) . After development, t h e zones a r e scrapped from t h e p l a t e s and d i s s o l v e d i n d i l u t e n i t r i c a c i d . The a c i d s o l u t i o n i s evaporated and t h e r e s u l t i n g r e s i d u e i s d i s s o l v e d i n anhydrous e t h a n o l - a c e t o n e (3:97), 3% methanolic KOH is added and t h e e x t i n c t i o n of scopolamine a t 575 nm i s measured w i t h i n 1 minute. The c o n c e n t r a t i o n o f t h e s u b s t a n c e i s determined by r e f e r e n c e t o a c a l i b r a t i o n graph. Q u a n t i t a t i v e d e t e r m i n a t i o n o f scopolamine by TLC-fluorimetry h a s been d e s c r i b e d ( 1 2 6 ) . The method depends on measurement o f t h e f l u o r e s cence o f scopolamine s p o t s a f t e r h e a t i n g w i t h H2SO4. The f l u o r e s c e n c e i s measured with a Turner f l u o r o meter f i t t e d with a r e c o r d e r . TLC system i s as follows :


534

K i e s e l g e l G l a y e r s , and t h e s o l v e n t c o n s i s t s o f anhydrous e t h a n o l - c o n c e n t r a t e d H2S04 (39:7 by weight), l e n g t h o f run 7 cm. After development, p l a t e s are d r i e d f i r s t i n a i r and t h e n by h e a t i n g a t 170' €or 45 minutes. (The absorbent must be f r e e from s u b s t a n c e s t h a t f l u o r e s c e under c o n d i t i o n o f t h e method). Rectil i n e a r response was o b t a i n e d up t o a l e v e l o f 6 pg a l k a l o i d (126). S t a b i l i t y o f scopolamine H B r i n eye drops can be i n d i c a t e d by TLC systems ( 1 2 7 ) : Scopolamine and i t s decomposition p r o d u c t s s c o p i n e , aposcopolamine (apohyoscine) and t r o p i c a c i d can be i d e n t i f i e d by TLC on k i e s e l g e l G , R f v a l u e s i n f i v e s o l v e n t systems a r e r e p o r t e d . Other TLC system have a l s o been r e p o r t e d (128,129). 9.6.4

Gas Liquid Chromatography (GLC) ManyGLC systems have been r e p o r t e d f o r t h e i d e n t i f i c a t i o n and q u a n t i t a t i o n o f t r o p a n e a l k a l o i d s i n c l u d i n g scopolamine.

System I : T h i s system was recommended t o d e t e r mine a t r o p i n e and scopolamine q u a n t i t a t i v e l y i n t h e i r crude drugs (130). E x t r a c t i o n : Alkaloids a r e e x t r a c t e d from a sample o f powdered belladonna o r stramonium (log) by t h e method o f USP X V I I f o r t o t a l a l k a l o i d s o f belladonna l e a f . 2 p l a l i q u o t s of t h e e x t r a c t a r e a p p l i e d i n duplicate. Column c o n d i t i o n : Glass (6 f t . x 0.075 inch i . d . ) packed with 2.5% SE-30/S on a c i d washed s i l a n i z e d Chromosorb G (80-100 mesh). Temperat u r e programmed from 150' t o 275' a t '6 p e r m i n u t e . I n l e t p o r t maintained a t 315'. C a r r i e r gas : Helium (100 ml/minute). Detection : Flame i o n i z a t i o n . C a l c u l a t i o n : After development, t h e peak areas a r e measured, The p r e c i s i o n f o r each a l k a l o i d i s s +2.5% and t h e method is q u a n t i t a t i v e f o r amounts i n t h e range 2 pg t o 53 mg (130).


535

System 11 : The following system was r e p o r t e d f o r q u a n t i t a t i v e d e t e r m i n a t i o n o f scopolamine and a t r o p i n e p l u s hyoscyamine i n u n i t d o s e s o f t a b l e t s and e l i x i r s (131). E x t r a c t i o n : A u n i t dose form c o n t a i n i n g 6 pg scopolamine 100 pg a t r o p i n e p l u s hyoscyamine i s e x t r a c t e d . The e x t r a c t and washing i s evaporated t o 0.1 m l and 1 t o 2 111 are submitted t o t h e system. Column c o n d i t i o n : Glass column (60cm x 3mm i . d . ) c o n t a i n i n g 3% OV-17 on Gas Chrom Q (80-100 mesh), Column i s maintained a t 210'. C a r r i e r gas : Helium (60 ml/minute). D e t e c t i o n : Flame i o n i z a t i o n . C a l c u l a t i o n : The peak h e i g h t r a t i o i s measured and t h e c o n c e n t r a t i o n o f each a l k a l o i d i s c a l c u l a t e d from c a l i b r a t i o n graph. The c o - e f f i c i e n t o f v a r i a t i o n ( 1 0 - d e t e r m i n a t i o n s ) a r e : f o r scopolamine t 4.8%, f o r a t r o p i n e p l u s hyoscyamine +2.5%.

System 111 : This system has been d e s c r i b e d as a simplified quantitative analysis of atropine and o t h e r a l k a l o i d s i n s c o p o l i a e x t r a c t i n c l u d i n g scopolamine. The method i s a l s o a p p l i e d t o g a s t r o i n t e s t i n a l drugs o f t h e s e a l k a l o i d s (132). The a l k a l o i d s ( a t r o p i n e , scopolamine and o t h e r s ) a r e separated a s t h e i r t r i m e t h y l s i l y l derivat i v e s . Diphenhydramine i s used a s i n t e r n a l standard. Column c o n d i t i o n : A column (1 m x 3 mm) packed with 0.75% o f Dexsil 300 GC on Gas-chrom Q, column temperature i s maintained a t 180'. C a r r i e r g a s : Nitrogen (40 m l min-I). Detection : Flame i o n i z a t i o n . C a l c u l a t i o n : The c a l i b r a t i o n graphs (peakheight r a t i o vs alkaloid content) i s r e c t i l i n e a r €or 25 t o 75 ng o f a t r o p i n e and 2.5 t o 7.5 ng o f scopolamine. Many o t h e r GLC have been r e p o r t e d f o r t h e i d e n t i f i c a t i o n o f scopolamine and o t h e r t r o p a n e a l k a l o i d s . S e v e r a l o f t h e s e systems a r e shown i n t a b l e 8.

Table 8 Column condition

: The GLC of Scopolamine

Carrier gas, Gas flow

Detect o r

Retention time (tR) *I Index (RI)

I.

1%SE-30 on 100-120 mesh Anakrom ABS, 6 f t . x 4 mm i.d., b o r o s i l i c a t e glass. Temperature 250'

Argon , 80 ml/minute

Argon i o n i z a t i o n o r Flame ionization

t R 0.89 ( r e 1a t i v e t o codeine)

11.

2.5% SE-30 on 80-100 mesh Chromosorb W, 5 f t . x 4 m i.d., g l a s s . Temperature 225'

Nitrogen , 50 ml/minute

Flame i o n i z a t i o n H2, 50 ml/minute, a i r flow 300 m l p e r minute

t R 0.84 (relative t o codeine)

Argon , 80 ml/minute

Flame i o n i z a t i o n

t R 10.7 (relative t o diphenhydramine)

Nitrogen ,

A s f o r system I1


Flame i o n i z a t i o n , Hydrogen 22 m l / minute


111. 3% QF-1 on 100-120 mesh Anakrom ABS, Temperature 200'

IV.

V.

3% XE-60 s i l i c o n e n i t r i l e polymer on 100-120 mesh Chromosorb W. Temperature 2 25 ' 5% SE-30 on 60-80 mesh Chromosorb W AW, 5 f t . x 1/8 inch i.d., stainless steel. Temperature 230'

50 ml/minute

Nitrogen, 30.7ml/minute

I

Ref.

(133)

(135)

I

Column c o n d i t i o n

VI.

2.5% SE-30 on 80-100 mesh Chromosorb G ( a c i d washed and dimethyldichlorosilane treated) , 2m x 4mm i . d . , g l a s s . Temperature 100-300°.

V I I . 3% Poly A103 on 80-100 mesh Chromosorb W YP, l m x 4mm i . d . , g l a s s . Temperature 200°. VI

2

R e t e n t i o n time (tR) It Index (RI)

Detect o r

C a r r i e r gas, Gas flow Nitrogen, 45 ml/minute

-

Nitrogen, 60 ml/minute

Ref.

R I 2303 (Reference = na l k a n e s w i t h an even number of carbon atoms)

( 136)

R I 2885 (Reference as i n system VI).

(137)

VIII. 3% OV-17 on 100-120 mesh Chromosorb W-HP, 6 f t . x 2mm i . d . , g l a s s . Temperature 150-250'.

Nitrogen, 50 ml/minute; a i r , 120 ml/minute; hydrogen 2 m l / minute

N-FID

R I 2729 (Reference = methagual on)

(138)

3% OV-1 on 100-120 mesh Chromosorb W-HP, 6 f t . x 2mm i . d . , g l a s s . Temperature 150-250°, i n i t i a l t i m e 8 minutes.

as f o r system VIII

N-FID

R I 2329 (Reference = 2-amino-5-chlorobenz ophenone)

(138)

IX.

I

I

Other GLC t e c h n i q u e s have a l s o been r e p o r t e d (127, 139-145).

I

538


9.6.5

High Performance Liquid Chromatography (HPLC) System I :

The f o l l o w i n g HPLC system has been a p p l i e d t o t h e s e p a r a t i o n and q u a n t i t a t i v e d e t e r m i n a t i o n of tropane alkaloids including scopolamine (146)

.

cozm :

A s t a i n l e s s s t e e l column (lm

x

4.6mm i . d . ) d r y packed with S i l X adsorbent.

Procedure : Samples were d i s s o l v e d i n methanol and i n j e c t e d d i r e c t l y i n t o t h e column

.

Mobi Ze phase :

A mixture of ammonium hydroxide

(28% NH3 by weight i n water) and tetrahydrofuran i n t h e r a t i o 1 : l O O v/v.

Detection : D i f f e r e n t i a l R e f r a c t i v e Index d e t e c t o r having a range o f 1.301.45 R I u n i t s and a high s e n s i t i v i t y UV d e t e c t o r ( a t 254 nm).

The average deviation i n integrator counts, over a concentration range of 5-5Opg was within t 1% f o r a21 the aZkaZoids examined. System I1 : This system i s a reversed-phase l i q u i d chromatography o f b a s i c drugs ( i n c l u d i n g scopolamine) and p e s t i c i d e s with a f l u o r i g e n i c i o n p a i r e x t r a c t i o n d e t e c t o r (147).

Colm :

*

SoZvent :

-

Two t y p e s were used: 10 cm x 3 mm ( i . d . ) packed chemic a l l y bonded 10pm s i l i c a g e l of t h e d i o l and CN t y p e o f Lichros o r b RP-2, RP-8 and RP-18. Micro-Pack CN-10 column (30 cm x 4 mm i . d . ) . 25% methanol i n water c o n t a i n i n g 0.1N NaH2P04 (pH 3 . 5 ) .

Detection : Ion p a i r e x t r a c t i o n d e t e c t o r € o r t h e s e n s i t i v e and s e l e c t i v e f l u o r e scence d e t e c t i o n .


539

System 111 : The f o l l o w i n g HPLC system was recommended f o r a n a l y s i s and q u a n t i t a t i o n o f belladonna a l k a l o i d s and can b e a p p l i e d t o e l i x i r s , t a b l e t s and c a p s u l e s o f t h e s e a l k a l o i d s c o n t a i n i n g phenobarbitone (148).

Extraction : The sample i s t r e a t e d w i t h H2SO4 and mixed w i t h CH2C12, a f t e r shaking, t h e organic layer i s discarded. Carbonate b u f f e r s o l u t i o n (pH 9.4) is added t o t h e aqueous p h a s e and t h e mixture i s extracted with CH2C12. The o r g a n i c phase i s f i l t e r e d , evaporated, theophylline (as internal s t a n d a r d ) i s added and t h e s o l v e n t evaporated t o d r y n e s s . The r e s i d u e i s t r e a t e d w i t h MeOH-HC1 and evapor a t e d t o dryness, t h e r e s i d u e i s r e - d i s s o l v e d i n methanol and t h e m e t h a n o l i c s o l u t i o n i s a g a i n evapor a t e d t o d r y n e s s . The f i n a l r e s i d u e i s d i s s o l v e d i n water and a p p l i e d t o t h e f o l l o w i n g HPLC system.

x 4mm) o f

cozwnn :

A s t a i n l e s s s t e e l (25cm S p h e r i s o r b ODS (5pm).

Mobile phase :

Water-methanol (21:10, pH 2.0) c o n t a i n i n g t e t rame t h y 1ammonium phosphate (0.8 m l m i n . - l ) .

Detection : UV a t 2 2 0 nm.

- The c a l i b r a t i o n graphs were r e c t i l i n e a r i n t h e r a n g e o f 0-0.5 mg m l - 1 (hyoscyamine p l u s a t r o p i n e ) , 0-0.32 mg m l - 1 (scopolamine). - The c o e f f i c i e n t o f v a r i a t i o n was 1.4% f o r scopolamine and 0.5% €or hyoscyamine. - The d e t e c t i o n l i m i t was 0.02vg f o r each alkaloid. - Recovery of t h e compounds was 93.0 t o 106.1% (148). Many o t h e r HPLC systems have been r e p o r t e d f o r i d e n t i f i c a t i o n and q u a n t i t a t i o n of s c o p o l a mine and o t h e r t r o p a n e a l k a l o i d s . S e v e r a l o f t h e s e a r e p r e s e n t e d i n t h e f o l l o w i n g t a b l e 9.

Table 9 : HPLC of Scopolamine Column 1-

Stainless steel, (30cm x 4mm), packed with 1.1Bondapak C 1 8

2-

A 12.5cm x 4.9mm packed with s i l i c a (spherisorb Sg W,

5m)

S t a i n l e s s -s t eel 3-

A 250x4 mm2 of

RP-18 (loum)

4-

A 15cm x 4.6mm

of Shodex ODS pak. 5-

A 30cm x 3.9mm

of 1.1 Bondapak C 1 8 (10 urn)

I

I

Mobile Phase

I n t e r n a l Standard

0.1M N a decyl s u l f a t e 0.1M NH4NO3 i n aqueous 60% methanol o r 55% ethanol.

Benzphetamine hydrochloride

A s o l u t i o n containing

1.175 g (0.01M) of ammonium perchlorate i n 100 m l methanol adjusted t o pH 6 . 7 by 1 m l of 0.1M NaOH i n methanol 156 g a c e t o n i t r i l e + 344 g phosphate b u f f e r (4.8 g 85% H3PO4 and 6. 66 g KH2PO4) pH 2.3 flow rate 1 ml/minute ( i s o c r a t i c a l l y ) 50% methanol (adjusted t o pH 4.0 with a c e t i c acid) containing 5mM sod. hept ane- 1- s u l f onat e

3% aqueous a c e t i c a c i d methanol (7:3 f o r detection, 3:l f o r determination) (lml min-l)

Ref.

UV at 254nm

(149)

UV/electro-

(150)

I W a t 220~2.~ (138) Rel. t R O f scopolamine N-butylbromide 1.02

MPH = 5-(p-methylphenyl) -5-phenylhydrant o i n

.

Detect o r

I

UV 215nm

I (151)

(1i m i t s 0.151J.g) L-Hyoscyamine, scopolamine HBr.

UV 254nm

(152)


541

Other HPLC have a l s o been r e p o r t e d (153155). F u r t h e r important r e f e r e n c e s on v a r i o u s chromatographic t e c h n i q u e s were found i n t h e l i t e r a t u r e s (156-158). 9.7

Radioligand Assay Methods A simple- and s e n s i t i v e r a d i o l i g a n d binding a s s a y i s d e s c r i b e d f o r t h e d e t e r m i n a t i o n o f scopolamine i n human u r i n e . A s a measure f o r t h e drug c o n c e n t r a t i o n , t h e q u a n t i t a t i v e displacement o f scopolamine o f t r i t i a t e d q u i n u c l i d i n y l b e n z y l a t e from r a t b r a i n r e c e p t o r s was used. The a s s a y is s e n s i t i v e t o c o n c e n t r a t i o n s a s low as 1 . 2 ng/mL. I t can be performed e a s i l y and q u i c k l y , a l s o no p r i o r e x t r a c t i o n procedure i s r e q u i r e d . Scopoline and s c o p i n e , p o s s i b l e m e t a b o l i t e s o f scopolamine do n o t i n t e r f e r e with t h e a s s a y (54).

A n t i c h o l i n e r g i c drugs i n c l u d i n g scopolamine i n d i c a t i n g t h a t t h e i r i n c u b a t i o n with m u s c a r i n i c r e c e p t o r a t 0' b e f o r e and a f t e r a d d i t i o n o f t h e r a d i o l a b e l l e d l i g a n d ['HI dexetimide can p r o v i d e lower d e t e c t i o n l i m i t s (by a f a c t o r o f 2.5 t o 9) with c o e f f i c i e n t o f v a r i a t i o n 3 t o 9% (159). Acknowledgement The a u t h o r s would l i k e t o thank M r . Uday C. Sharma, Department o f Pharmacognosy, College o f Pharmacy, Riyadh, Saudi Arabia f o r h i s v a l u a b l e and s i n c e r e e f f o r t s i n t y p i n g t h i s manuscript.


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SULFOXONE SODIUM

Vijay K. Kapoor Department of Pharmaceutical Sciences Panjab University Chandigarh 160014, India 1.

Introduction

2.

Description 2.1 Namer Formula and Molecular Weight 2.2 Appearancer Color and Odor

3.

Physical Properties 3.1 Optical Rotation 3.2 Melting Range 3.3 Solubility

4.

Synthesis

5.

Stability

6.

Biological Activity

7.

Metabolism and Pharmacokinetics

9.

Methods of Analysis


553

Copyright D 1990 by Academic Press, Inc. All nghts of reproduction in m y form reserved.

VIJAY K. KAPOOR

554

10.

9.1

Elemental Composition

9.2

Identification Tests 9.21 Color Tests 9.22 Pharmacopeial Tests

9.3

Spectrophotometric Analysis 9.31 Colorimetric 9.32 Fluorometric

9.4

Chromatographic Analysis

References

555

SULFOXONE SODIUM

1.

Introduction

Sulfoxone sodium belongs to the class of sulfones which are derivatives of 4,4'-diaminodiphenylsulfone (dapsone, DDS). The sulfones were synthesized on analogy of sulfonamides. Dapsone was found in 1937 to be thirty times more active as sulfanilamide when used in streptococcal infections in mice. In the 1940s sulfones were found to be effective in suppressing experimental infections with the tubercle bacillus and for rat leprosy. The usefulness of sulfones in the chemotherapy of human tuberculosis was very limited, but their cl'n cal trials in h u m p leprosy were successful. i#$ The sulfones are presently the most important drugs for the treatment of leprosy. Sulfoxone sodium acts through I t s conversion to dapsone in the body. 2.

Description 2.1

Name, Formula and Molecular Weiqht

Sulfoxone sodium is also known as sodium sulfoxone, aldesulfone sodium8 and as sulfoxydiasulfone sodium. Chemically, it is disodium [sulfonylbis ( phenyleneimino) Idimethanesulfinate. Other chemlcaf-names are: dlsodiyn salt of [sulfonylbis (1,4=phenyleneimino)Jbismethanesulfinic acid; disodium 4,4'-dlaminodiphenylsulfone bisformaldehydesulfoxylate; disodium formaldehydesulfoxylate diaminodiphenylsulfone. The CAS registry number for sulfoxone is 144-76-3, and for sulfoxone sodium is 144-75-2. The proprietary name f o r sulfoxone sodium is Diasone or Diasone Sodium.

C14H14N Pa2'6'

3

Molecular Weight: 448.43

VIJAY K. KAPOOR

556

2.2

Appearance, Color and Odor

A white to pale yellow powder w i t h a characteristic odor. Sulfoxone sodium USP is a mixtur of disodium [sulfonylbis(E-phenyleneimino)Tdimethanesulfinate and suitable buffers and inert ingredients. It contains not less than 73.0 per cent and not more than 81.0 per cent of C14H14N $?a206S3, calculated on the dried basis

3.


activity

Optical Rotation

.

Sulfoxone sodium exhibits no optical

Melting Range The melting range3 of sulfoxone sodium after drying at 100-llOo is 263-265O (decomp). Another report mentions the melting point of amorphous product as 268O (decomp).4 3.3

Solubility

Sulfoxone sodium is soluble (1 in about 14) of water yielding a clear to hazy pale yellow s ~ l u t i o n . ~A lC% solution in water ha6 a pH of Sulfoxone sodium is very slightly 10.5 to 11.5. soluble in alcohol, chloroform, and ether .5 4.

Synthesis

Sulfoxone sodium was prepared by Raiziss et a1 . by adding finely powdered sodium formaldxydesulfoxylate (OHCH2S02Na) to a solution of 4,4'diaminodiphenylsulfone in specially denatured alcohol, and refluxing the mixture for five hours on a steam bath. The sulfoxone sodium is obtained as a tetrahydrate amorphous powder in 95% yield by this method. Sulfoxone sodium was also independently prepared using a different method by In the latter method Bauer and Rosenthal.6'8 the combination of 4,4D-diamlnodiphenylsulfone

557

SULFOXONE SODIUM

0

Sulfoxone Sodium

Scheme I

-

Synthesis of Sulfoxone Sodium

VlJAY K . KAPOOR

558

0

0

Sutfoxone Sodium

Scheme I1

-

Alternate Synthetic Route to Sulfoxone sodium

with sodium formaldehydesulfoxylate was done in glacial acetic acid. Upon addition of alcohol to the neutralized aqueous solution the reaction product crystallized as n edles with two moles of water of crystallisation.g Schemes (Scheme-I, Scheme-114) for complete synthesis of sulfoxone

559

SULFOXONE SODIUM

sodium have also been described. 48 Other synthetic routes to 4,4'-diaminodiphen lsulfone (dapsone) have been reported earlier. 11 Preparation of a salt of sulfoxone sodium w i t h antimalarial amodlaquin, useful against Plasmodium berghei infection, has been reported.12 5,

Stability

The combination of 4,4a-diaminodiphenylsulfone and sodium formaldehydesulfoxylate in sulfoxone sodium is reported3 to be firm and can withstand the splitting effect of various agents. In sealed glass ampoules under high vacuum sulfoxone sodium remains water-soluble indefinitely. Exposed to air for several days it undergoes some change that renders part of it insoluble, but mixed w i t h small amount of sodium bicarbonate it remains unchanged for several months and is easily soluble in water.308 A 0,4% hydrochloric acid solution at 37. does not, over a period of 2 hours, cause splitting off of the formaldehydesulfoxylate or liberation of 4,4'-diaminodiphenylsulfone. Acetic acid or carbon dioxide merely causes precipitation from alkaline solutions and the precipitate redissolves on adding alkali. 3 United States Pharmacopeia recommends that sulfoxone sodium be preserved in tight, light-resistant Containers under the atmosphere of nitrogen, in a freezer.13 6,

Bioloqical ActiviQ

Sulfoxone sodium was prepared in a successful attempt to reduce the toxicity of 4,4'-diaminodiphenylsulfone (dapsone), and w a s reported to have a therapeutic index considerably greater than that of the latter.14 Sulfoxone sodium w s found to be decidedly less toxic than dapsone.15*16 ef fectivs Sulfoxone sodium was also found to It was, agent in experimental tuberculosis. however, found ineffective clinically as suppressive in human tuberculosis. 27 There are several reports on the effectiveness of sulfoxone sodium in experimental toxoplasmosis.~8-~~Sulfoxone has also been studied for e erirnental meningococcus infection in mice. It showed no

e-32

3

VIJAY K. KAPOOR

560

bacteriostatic activity & vitro against Paracoccidioides brasiliensis33, E b e m l a t hosa --fast baci llf isolated from + jepers q8 or on and Stefansky's bacillus.35 Powell et al. 36 have indicated a potential role of s u n o s e in the prevention and treatment of Infections with chloroquin-resistant Plasmodium are other reports on different ties involving sulfoxone gy and other related as ects of sulfoxone sodlum have been reviewed. 418 45 Therapeutically sulfoxone sodim is used for the treatment of leprosy. It has actions similar to those of dapsone and is given to patients who experience se ere gastrointestinal side-effects with dapsoneOg In higher doses it is used for dermatitis herpetiformis. The mechanism of action of sulfones is probably similar to that of the sulfonamides since both interefere with incorporation of aminobenzoic acid Into dehydrofolate 8 2 The possi le relation between the fact that sulfoxone enters washed mycobacterial cells and the mechanism of bacteriostasis has been discussed.43 Total protein, total globulin, pseudoglobulin and euglobulin concentratlons of the serums of lepers varied greatly with the progress of the disease. Higher values for these fractions have been found in advanced cases than in earlier cases. It has been observed that after six months treatment with sulfoxone most of the protein fractions decreased, especially euglobulin.44 It has also been reported that compounds which inhibited phenoloxidase of Mycobacterium leprae also suppressed Its multiplication in mice, suggesting that phenolase mi ht be of metabolic significance to the organisrn.42 Electron micrographs of A I shadowed ,M. le rae from patients treated with sulfoxone showe swellingofthe cytoplasm and a granular state of M. le rae and a disappearance of the peripheral Eal*Swislocki et a1.47 have discussed the mechanism of effec- Z€ sulfones, and have reported that sulfoxone increased the activities of adenylate cyclase and protein kinase in erythrocytes.

.

%-

%

Regarding the mechanism of action of sulfoxone sodium in the treatment of dermatitis herpetiformis,

SULFOXONE SODIUM

561

it has been observed48 t h a t t h e drug i n h i b i t s both neutrophil iodination and q t o t o x i c i t y f o r tumor cells, T h i s may represent an important mechanism by which sulfoxone sodium produces i t s therapeutic effect when used t o t r e a t inflammatory skin disease. 7.

Metabolism and Pharmacokinetics Metabolism of sulfoxone sodium has been

studied by Francis and Spinks.49 The drug gets hydrolysed i n t h e g a s t r o i n t e s t i n a l t r a c t t o 484'diaminodiphenylsulfone (dapsone; DDS) I t was shown t h a t t h e therapeutic effects of sulfoxone

sodium are closely r e l a t e d t o the blood concentr4, 4'ations of 4,4'-diaminodiphenylsulfone.4g~50 Diarninodiphenylsulfone a f t e r absorption i s metabolised t o a number of productsll; monoacetyldapsone (MADDS) being one of t h e major metabolites.

4,4~-Diaminodiphenylsulfone (DDSl8R=H

Monoacetyldapsone (MADDS),

R=-COCH3

Several pharmacokinetic studies have been done The concentration of on sulfoxone sodium.41,51-56 sulfoxone i n the blood of fortyseven p a t i e n t s receiving o r a l l y 1 g of t h e drug d a i l y f o r 1 t o 4 years8 varied from 0 t o 3.6 mg X ; t h maximum concentration i n urine was 100 mg x,fl f i e sulfoxone concentration i n t h e u r i n e of twentyone patients. receiving 0.66 g d a i l y was 3 2 mg %.51 Determination i n blood, urine, t i s s u e and faeces of thirtytwo biopsied lepers t r e a t e d w i t h sulfoxone f o r 4 months t o 7 years led t o the conclusion t h a t sulfoxone i s retained i n t h e body up t o 2, metimes up t o 4 weeks after cessation of treatment. 53 some amount of t h e drug was found i n t h e faeces, Excretion occurs through t h e kidney rapidly but may be disturbed by abnormal i n t e s t i n a l or impaired

W A Y K. KAPOOR

562

renal function. A tendency t o storage i n the skin e x i s t s f o r sulfoxone. Liver, spleen, kidneys nerves a l s o serve as organs of concentrations. I n another study54 free and combined sulfone were found i n t h e blood of 47.3% of the lepers 24 hours a f t e r t h e end of treatment w i t h sulfoxone sodiumo Intravenous i n j e c t i o n of sulfoxone sodium i n f i v e t i m e s t h e doses used f o r human therapy caused hemolysis i n dogs. The hemolysis seemed t o be proportional t o t h e rate of hydrolysis and libera t i o n of 4,41-diaminodiphenylsulfone. The blood concentration of 4,4'-dlaminodiphenylsulfone reached i t s rnaximum 30 min after injectionO55 The disposition of the water-soluble sulfones i n man was determined earlier b applying t h e Bratton and Marshall p r ~ e d u r e 5f o~ r measuring aromatic amines .58 subsequent1 a n a l y t i c a l techniques were developed which cou d measure small amounts of 4,41-diaminodiphenylsulfone i n This made possible a r e a l i s t i c plasma.59-62 assessment of t h e DDS levels obtained i n p a t i e n t s t r e ed w i t h water-soluble sulfones. Peters et have studied t h e disposition o f sulfoxone sodium i n leprosy p a t i e n t s by determining t h e l e v e l s of dapsone (DDS) and monoacetyldapsone (MADDS) i n plasma and urine by spectrophotofluorometric technique. Peak plasma l e v e l s of DDS were approximately 600 ng/ml f i v e t o e i g h t hours after treatment w i t h 330 mg sulfoxone sodium given orally. Because 330 m g sulfoxone contain 169 mg DDS, assuming complete hydrolysis t o DDS, it could be estimated t h a t an approximately t h r e e f o l d higher molar dose of sulfoxone than of DDS w a s required t o y i e l d similar plasma levels of DDS. The urinary excretion pattern of DDS and MADDS a f t e r t h i s drug was similar t o that found after DDS t r atment, but t o t a l DDS excretion was lower. Smith4f a l s o reported a large difference i n t h e urinary excretion of t o t a l DDS during three days following o r a l sulfoxone and DDS by p a t i e n t s (55% versus 80%), and concluded t h a t t h i s was due primarily t o r e l a t i v e l y poor absorption of sulfoxone from t h e g a s t r o i n t e s t i n a l t r a c t . The r e s u l t s of investiga t i o n by Peterset a1.56 indicate t h a t regular sulfoxone therapy provides plasma l e v e l s of DDS t h a t would be expected to be therapeutically e f f e c t i v e and t o protect p a t i e n t s from the development of DDS-resistant leprosy.

Bd

1'

SULFOXONE SODIUM

563

The bioequivalence requirements of sulfoxone sodium have been glven.63

Bauer 8 studied t h e t o x i c i t y and therapeutic a c t i v i t y of sulfoxone sodium i n streptococcal infection in m i c e , and has described 3 g per kg as minimum t o l e r a t e d dose of the drug given subcutaneously; w h i l e minimum e f f e c t i v e dose described is 0.2 g per kg. A marked reduction i n the red blood c e l l count and hemoglobin l e v e l of t h e p a t i e n t s receiving 1 g of sulfoxone odium f o r 120 days or more has been reported, 18 Primaquin s e n s i t i v e erythrocytes w e r e found t o be unusual1 susceptible t o hemolysis by s u l f oxone sodium.640 g5 Several severe untowards effects caused by dapsone and i t s analogs have been descrj.bed.182 Beside8 frequent g a s t r o i n t e s t i n a l and c e n t r a l nervous system disturbances, t h e most common untoward effect is hemolysis of varying degree. Development of peripheral neuropathy of thumbs and hand, without motor involvement, i n a p a t i e n t receiving sulfoxone sodium f o r dermatitis h e r p e t i f o m i s has been reported. 66 The U n i t e d States Pharma~opeia'~gives t h e following s a f e t y t e s t f o r sulfoxone sodium. Prepare a solution of sulfoxone sodium (1 i n 10). Select 15 mice, each weighing between 20 and 25 g r and divide them i n t o three groups of f i v e each. Administer o r a l l y t o each mouse of the f i r s t group 20 )zL of t h e solution per g of body weight, I n the same manner administer t o each mouse of the second group and to,each mouse of the t h i r d group 25 and 30@, respectively, per g of body weight: a l l of the mice of t h e first group, a t least four of the second group, and a t least two of t h e t h i r d group survive for 5 days, 9.

Methods of Analysis 9.1

Elemental Composition

The elemental composition of sulfoxone sodium i s a s follows67:

W A Y K. KAPOOR

564

P e r cent

Element C

37.49

H

3.15

N

6.25

Na

10.26

0

21.41

S

21.45

The com o s i t i o n of sulfoxone sodium dihydrate is r e p o r t e d as follows:

Element

P e r cent Calcd.

N

5 078

5.64

S

19-86

19 e80

Na

9.50

9.24

9.2

P e r cent Found

I d e n t i f i c a t i o n Tests 9.21

Color T e s t s

The following color tests f o r t h e i d e n t i f i c a t i o n of sulfoxone sodium have been d e s c r i b dt A knifepoint of the material is A, placed on a square of blank newspaper and moistened with 2 . 3 hydrochloric acid and a drop or two of ethanol t o aid solution i f required, a deep yelloworange color i s p uced when examined against a The test is based on l i g n i n white color reactions with amine compounds.

B e F e i g l and Moscovici69 have described a color t e s t for t h e detection of sulfoxone sodium i n very small quantities. The color reaction is based on t h e evolution of formaldehyde when t h e drug is warmed with concentrated s u l f u r i c acid i n a water b a t h - The evolved formaldehyde can

SULFOXONE SODIUM

565

be detected in solution o r in the vapor phase by means of chrornotropic acid and concentrated sulfuric acid when a violet color is produced. The test has been recommended for the detection of sulfoxone sodium in pharmaceutical products .70 C. A bright red color is produced if sulfoxone sodium is heated with furfural-acetic acid and a drop of hydrochloric acid is added.71

D. An orange color is produced by treatment of sulfoxone sodium with dimethylaminobenzaldehyde -71 E. Sulfoxone sodium gives a blue color with a mixture of 1:l of 10% aqueou ammonium molybdate and concentrated sulfuric acid. 91

STe turbidity

F. A pink color and s is produced with silicotungstic acid. with 0.25%

G. A blue recipitate is produced methylene blue. 71

H. Distillation of 0.5 g of sulfoxone sodium with 50 mL of 50% hydrochloric acid gives distillate which decolorises 0 . E iodine solution. The distillate gives a blue color upon addition of morpholine hydrochloride in concentrated sulfuric acid.71

I. In alcoholic solution sulfoxone sodium gives a violet color with gold chloride.71 J. Mixed with 5 drops of 10% ferric chloride and 5 drops of potassium ferricyanide, sulfoxone sodium gives a sky blue color.71

9.22

Pharmacopeial T e s t s

The United States Pharmacopeia g identification tests for sulfoxone sodium

gives the follow

4%

A. Transfer about 350 mg to a 100-mL volumetric flask, dissolve in water, dilute with water to volume, and mix. Transfer 10.0 mL of

W A Y K. KAPOOR

566

t h i s solution t o a 100-mL volumetric f l a s k , d i l u t e with water t o volume, and mix. Transfer 4.0 mL of t h e r e s u l t i n g solution t o a s u i t a b l e flask, add 0.5 arL of hydrochloric acid, and hydrolyse in a boiling water bath f o r 30 minutes. Transfer the contents of t h e f l a s k t o a separator with t h e aid of water, add 2 mL of sodium hydroxide solution (1 i n 101, and extract w i t h t h r e e 25-mL portions of ethylene dichloride, F i l t e r the extracts

through a pledget of glass wool i n t o a 100-mL volumetric f l a s k and d i l u t e w i t h ethylene dichloride t o volume. The u l t r a v i o l e t absorption spectrum of the solution so obtained exhibits maxima and minima a t the same wavelengths as t h a t of a solution of USP Dapsone RS i n ethylene dichloride having a known concentration of 5 ~ 4 per concomitantly measured. B. T o 10 mL of a solution (1 i n 100) add 1 mL of iodine TS and 2 mL of chloroform,

shake vigorously, and allow the layers t o separate8 no color appears i n e i t h e r layer. C. I g n i t e 200 mg, t h e residue responds t o t h e tests f o r sodium.

9.3

Spectrophotometric Analysis 9.31

Colorimetric

A colorimetric method is empl t o assay sulfoxone s0dium.33 It involves aci hydrolysis of sulfoxone sodium t o liberate free amino groups followed by diazotization and coupli n g with E-1-naphthylethylenediamine t o form an azo dye. The absorbance is measured spectrophotometrically a t a wavelength of about 535 nm. A standard solution of dapsone 1s a l s o used i n the assay procedure which is as follows,

K*

Transfer about 1 g0 accurately

weighed, of sulfoxone sodium t o a 2000-mL volumetric flask, dissolve i n water, d i l u t e w i t h water t o volume, and mix. P i p e t 4 mL of the solution I n t o a 100-mL volumetric f l a s k , add 1.0 mL of E-toluene-

sulfonic acid solution and 0.5 mL of %-hydrochloric acid, and heat the f l a s k i n a boiling water bath f o r 30 minutes. Cool, d i l u t e w i t h water t o volume, and

SULFOXONE SODIUM

mix.

561

T h i s solution i s c a l l e d a s assaypreparation.

P i p e t 2 mL each of dapsona standard s o l u t i o n (prepared as directedl3; each mL of t h i s solution contains a known quantity of about lOpg of dapsone, equivalent t o 18.06 pg of C1#11fl2Na20gS3), t h e assay preparation, and water t o provide t h e blank, i n t o separate 25-mL volumetric f l a s k s . To each f l a s k add 2.0 r a l of hydrochloric acid, 10.0 mL of water, and 2.0 mL of sodium n i t r i t e solution, and mix. A f t e r 3 minutes, accurately timed, add 1.0 mL of ammonium sulfamate solution, and mix. Allow t o stand f o r 2 minutes, accurately timed, d i l u t e with g-l-naphthylethylenediamine dihydrochloride solution t o volume, i n s e r t t h e stoppers i n t h e f l a s k , and mix. A l l o w t o stand f o r 10 minutes, and concomitantly determine t h e absorbances of t h e solutions i n 2-cm cells, a t t h e wavelength of maximum absorbance about 535 nm, with a s u i t a b l e spectrophotometer, using t h e blank t o set t h e instrument. Calculate t h e quantity, i n rng of C1&1@2Na206S3in t h e sulfoxone sodium taken by t h e formula (448.43/248.30) (5OC) (Au/As), i n which 448.43 and 248.30 a r e t h e rnoiecular weights of C1@1@2Na206S3 and dapsone (C12H12N2025) respectively, i s t h e concentration, i n pg per a 8 of USP Dapsone RS i n the dapsone standard solution, and AU and AS a r e t h e absorbances of the s o l u t i o n s from t h e assay preparation and dapsone standard solution, respectively.

x-

9.32

Fluorometric

Fluorometric procedure has been employed i n pharmacokinetic tudy of sulfoxone sodium i n leprosy p a t i e n t s . 58 9.4

ChroxnatoqraDhic Analysis

Orzech have described various chromatographic procedures f o r t h e a n a l y s i s of dapsone, t h e a c t i v e conversion product of sulfoxone sodium i n t h e body.

WAY K.KAPOOR

568

10.

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SULFOXONE SODIUM

571

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0

78 (1949).

W.

smith0 Lepr. Rev.,

200

1 2 8 (1949)

.

D. Yegian and V. mddr J. Pharmacol., 318 (1945).

8 4 0

M.L.G. Uyguanco, J.N. Rodriguez and I. Concepcion, J. P h i l l i p i n e Med. ASSOC., 65 (1950); C.A.8 45, 4821b (1951).

2 6 8

K. Prabhakaran, E.B. Harris and W.F. Kirchheimer, Microbios, 2, 273 (1972); C.A., 77, 136758a (1972).

Malfatti and E.D.L. Jonquieres, I n t e r n . J. Leprosy, 2 0 323 (1953). H.G.

Swislocki, J. Tierney, J. Zinberg and S.R. P f e f f e r , Adv. Expo Med. Biol., 9 7 0 301 (1978); C.A.0 9 0 0 162139n (1979).

N.I.

J.A. Kazmierowski, J.E. ROSS, D . S . Peizner and K.D. Wuepper, J. C l i n . I m n o l . , i 0 55 (1984)

r a n c i s and A. Spinks, B r i t . J. Pharmacol., -J.5 , F565 (1950). H. Floch and N . R i s t , Rev. brasil. leprol., 18, 111 (1952); C.A., 47, 76591. (1953). S i s t e r H. ROSS, (1947); C.A., 4

Intern. J. Leprosy, 267a (1948).

20

150

E. T i t u s and J. Bernstein, Ann. N.Y. SCi. 8 5 2 8 719 (1949) S i s t e r H. ROSS, I n t e r n . J. Lepros , 1 333 (1950); C.A., 45, 6292h (1951f.

-

Acad. 8 0

S i s t e r H. Ross and F . G e m a r , I n t e r n . J. Leprosy, 1 9 8 153 (1951); C.A., 4 6 0 76456 (1952) 0

236

W A Y K. KAPOOR

572

55.

Rosenfeld, H. Rzeppa, L. Mahas and S. Schenberg, Mem. i n s t . Butanlan SSo Paulo,

G.

4 8 8 1570h

248 69 (1952) (Pub. 1953); C.A.8 -ti9541 0

G.R.

56.

J.H. P e t e r s , J.F. Murray. Jr., and R.R. Jacobson, Lepr. Rev.,

57.

A.C. Bratton. E.K. Marshall, Jr.8 D o Babbitt and A.R. Hendrickson, J. B i o l . Chem., 1 2 8 8

Gordon

4 6 8 171 (1975)

537 (1939).

238

58.

J.

59,

G.A.

60.

J.H.

Jr.,

P e t e r s , G.R. Gordon and W.T. C o l w e l l , J. Lab. C l i n . M e d . 0 7 6 0 338 (1970).

61.

J.F.

Murray,

owe,

Lepr. Rev.,

4 (1952).

E l l a r d and P.T. G a m m ~ n , I n t e r n . J. ~ e p r o s y ,3 7 8 398 (1969).

Jr.8

G.R.

J. Lab. C l i n . M e d o ,

Gordon and J.H.

78, 464

Peters,

(1971).

62.

J.F. Murray, Jr., G.R. G ~ r d o n ,C.C. and J . H . P e t e r s , J. Chromatogr., s (1975)

64.

E. Beutl@r, Proc. Intern. Congr. Haematol.,

65.

R.J. D e r n , E. B e u t l e r and A.S. Alving, J. Lab. C l i n . Med., 8 7 8 750 (1981).

66.

G.

67,

Merck Index, 10th Ed1108 M. Winaholtz, Ed., Metck & C O O r Inc., RahWay, N 0 J . r U.S.A.,

Volden, Br. Med. J.8

A 0

Gulledge 0 67

1193 (1977).

1983, Po 1287.

MOerke, J. Org. Chem.,

68.

G.A.

69.

F. F e i g l and R.

803 (195510

&

42 (1945) 0

Moscovicir Analyst, 80,

SULFOXONE SODIUM

70.

F. F e l g l and E. S i l v a , Drug Standards, 23, 113 (1955)t C.A., 50, 2117h (1956).

71.

T . S . Gloria, Anais fac. farm. e edontol. Univ. Sa'o Paulo, 11, 8 5 (1953) (Pub. 1954); C.A., 49, 5 6 6 ~(1935).

513

TENIPOSIDE 2

J. Jantina Kettenes-van den Bosch' Joost J.M. Holthuis 1 and Auke Bult

'University of Utrecht Department of Pharmaceutical Analysis Utrecht, The Netherlands. EuroCetus B.V. Paasheuvelweg 30 1105 BJ Amsterdam, The Netherlands 1. History 2. Description 2.1. Nomenclature, Formula, and Molecular Weight 2.2. Appearance, Odour, and Colour 3 . Synthesis

4. Physical Properties 4.1. Ultraviolet Spectrum 4.2. Infrared Spectrum 4.3. Fluorescence Emission Spectrum 4.4. Nuclear Magnetic Resonance Spectrum 4.5. Mass Spectrum 4.6. Melting Range 4.7. Differential Scanning Calorimetry 4.0. Optical Rotation 4.9. Dissociation Constant 4.10. Electrochemistry 5. Methods of Analysis

5.1.

5.2.

Thin Layer and Paper Chromatography High Performance Liquid Chromatography

6. Stability and Degradation

6.1. 6.2.

Stability in Aqueous Solutions Stability in Plasma


575

Copyright 0 1990 by Academic Press. Inc All nghts of reproduction in any form reserved

516

J. JANTINA KETTENES-VAN DEN BOSCH ET AL.

7. Pharmacology 7.1. Mechanism of Action 7.2. Pharmacokinetics 7.3. Clinical Activity 7.4. Clinical Toxicity 8. Analysis of Teniposide and Metabolites in Biological Matrices 8.1. Teniposide 8.2. Teniposide Metabolites 9. References

511

TENIPOSIDE

1.

HISTORY

Teniposide is a semi-synthetic derivative of epipodophyllotoxin and is closely related to etoposide [l]. It is used as a cytostatic in the treatment of several types of cancer. Teniposide was synthesized from podophyllotoxin in 1963, in the Sandoz Laboratories. Podophyllotoxin, the starting material for teniposide, is isolated from the dried roots and rhizomes of species of the genus Podophyttwn, such as the may apple or American mandrake ( P o d o p h y t h p e m ~ L.) and P0dophqth.m Wall.) C2l. The medicinal properties of podophyllin, the ethanolic extract of the roots and rhizomes of the above mentioned Podophqttum species have been known for more than 150 years. Podophyllin contains several podophyllotoxin derivatives, a number of which possess considerable anti-tumour activity. Podophyllotoxin itself proved to be the most active cytotoxic compound. However, the toxicity of naturally occurring podophyllotoxins prevents administration of doses high enough to give sufficient therapeutic effect. Therefore, a variety of derivatives were synthesized from natural podophyllotoxin in an attempt to find compounds with an acceptable therapeutic index [3-51. Teniposide was one of the promising compounds.

2.

DESCRIPTION

2.1.

Nomenclature, Formula, and Molecular Weight

The generic name is teniposide (29767-20-2). Other names arg VM 26, PTG, NSC 122819. The trade name of the drug is Vumon The Chemical Abstracts' name is I'-demethyl-l-O[4,6-0-(2-thenylidene)- 6-D-glucopyranosyllepipodophyllotoxin (IUPAC) or 5,8,8a,9-tetrahydro-5-(4-hydroxy-3,5-dimethoxyphenyl)-9-[[4 ,6-0-(2-thienylmethylene)-6-D-glucopyranosyl]-

.

oxy~-furo[3'4':6,7~naphtho~2,3-d]-1,3-dioxo1-6(5aH)-one. The molecular formula of teniposide is C32H32013S;

its molecular weight is 656.7. 2.2. powder.

Appearance, Odour, and Colour Teniposide

is

a

white , odourless and

amorphous

578

J. JANTINA IU3TM3NJ3S-VAN DEN BOSCH ETM.

OH

3.

SYNTHESIS OF TENIPOSIDE

The synthesis of teniposide from naturally occurring podophyllotoxin I (Scheme 1) is described in ref. [3-53. Podophyllotoxin is treated with HBr in lI2-dichloroethane, resulting in 1-brow-1-desoxyepipodophyllotoxin, which demethylates to l-bromo-4'-demethylepipodophyllotoxin (11) when the reaction mixture is kept at O°C for about 24 hours. By treatment of I1 with BaCO in an acetone/water mixture, the bromine is replaced by a 3hydroxyl group, resulting in 4'demethylepipodophyllotoxin (111). After protection of the phenolic hydroxyl with benzyl chloroformate, the 1-OH group is coupled with 2,3,4,6-tetra-O-acetyl-~-D-glucopyranose. The sugar moiety probably enters from the less hindered side, because glycosidation of podophyllotoxin itself also results in an epi product [4]. The protecting group at the 4'-OH is removed by hydrogenolysis with H2/Pd and the acyl groups by hydrolysis with Zn(OAC)2 in methanol. During the hydrolysis, about 30% of the compound is converted into a mixture of the hydroxy acid (by opening of the lactone ring) and the cib lactone. These products are easily removed by crystallization. The last step in the synthesis is the reaction with 2-thiophene carboxaldehyde, with ZnC12 as a catalyst. Of the 0-4,6 cyclic acetals, the isomer with the equatorial thienyl group predominates.

OH

cy(

OH

kH3

6t.i

O--COOCHz-O

m

n

I

IV

BF, / E I P

Wow 0 Ho

Ace*

c w

CHlDAc

CHPAc

Ad3*ACO

OACO

I

VI

I

V

Scheme 1. Synthesis of teniposide.

OAC

0 I

2.3.4.6. - T e n - 0 -9 - B- D - d m pyranose

J. JANTINA KETI'ENES-VAN DEN BOSCH E T A L .

580

Minor quantities of the axial isomer are eliminated in the purification procedure CS 1.

4.

PHYSICAL PROPERTIES

4.1.


The ultraviolet spectrum of a 71 pM solu-ion of teniposide in absolute methanol (Figure 1) showslgn absorption cIextinction (E1cm) at 283 nm maximum at 283 nm. The sR cifis 64.1 ( E = 4209 l.ml .cm ) [6]. The ultraviolet spectrum was recorded with a double beam Shimadzu Spectrophotometer W - 2 0 0 in a 1 cm silica cell.

I

0.1 A.U.

260

300

nm

360

Figure 1. The ultraviolet spectrum of teniposide (71 pM) in methanol.

581

TENIPOSIDE

4.2.

Infrared Spectrum

The IR spectrum of teniposide (KBr tablet) is shown in Figure 2. The spectrum was recorded with a Jouan-Jasco IRA-1 grating infrared spectrometer. Characteristic bands are the carbonyl stretTh vibration of the strained m n d lactone ring at 1785 cmthe OH stretch vibra ion of the phenolic and sugar OH groups at 3540 p d 3400 cm , the aromatic bands at 1605, 1505 "d 1485 cmand C-0 stretch vibrations at 1230 and 1100 cm

-5

4.3.

.

Fluorescence Emission Spectrum

The fluorescence emission spectrum of teniposide (Figure 3) was recorded with a Kontron SFM 25 fluorimeter. An excitation wavelength of 295 nm and a scan rate of 60 nm/min were used. 4.4.

Nuclear Magnetic Resonance Spectrum

The proton NMR was recorded in deuterochloroform containing a drop of dimethyl sulfoxide-d with a Bruker AM-500 spectrometer at a frequency of SbO.14 MHz. The internal standard was DMSO (at 2.49 p.p.m.1. The spectrum between 2.7 and 5.3 p.p.m. is reproduced in Figure 4. Chemical shift assignments (Table I) were made on the basis of integrated intensity measurements and comparison with the spectrum of etoposide [ 7 ] . Coupling constants for ring C and D protons, and for the glucose and the thienyl moiety are given in Table 11. The natural abundance I3C NMR spectrum was recorded with a Bruker SP-200 WB instrument at a frequency of 50.3 MHz, with deuterochloroform containing a drop of dimethyl sulfoxide-d6 as the solvent. DMSO (at 39.5 p.p.m.1 was used as the internal standard. The proton-noise decoupled spectrum is reproduced in Figure 5; the spectral assignments are presented in Table 111. Since some of the chemical shift values differ only slightly, the assignments for the corresponding signals may be interchanged.

J. JANTINA KEl'TENES-VAN DEN BOSCH ETAL.

582

(MICRONS) "0

,oo2{

4;

5.;

7p

6;

8.;

9.0

l~,lZ.,Oi,4;"

1

4000

3600

3200

2800 2400

2000

1800

1400

1600

1200

loo0

800 650

an-' Figure 2. The infrared spectrum of teniposide.

I

I

I

300

350

400

nm

Figure 3. The fluorescence emission spectrum (not corrected) of teniposide (9.4 pM) in methanol.

583

TENLF'OSIDE

I 4.5

I

5.0

4.0 1

1

3.5

310 chemical shift (p.p.m.1

Figure 4. Proton NMR spectrum ( 2 . 7 - 5 . 3 p.p.m.1 teniposide.

I 180

I

I

160

140

I 120

I 100

I 80

I

I

60

40

of

I 20

I 0

chemical shift (p.p.m.1 Figure 5 . 1 3 C NMR spectrum of teniposide.

J. JANTINA KE'ITENES-VAN DEN BOSCH ETAL.

584

Table I.

H'

NMR assignments for teniposide in deuterochloroform.

chemical shift 6 (p.p.m.1

,-b

multiplicity

2.89 3.31 3.42 3.45 3.47 3.58 3.69 3.74 4.21 4.28 4.42 4.51 4.57 4.96 5.10 5.78 5.94 6.24 6.49 6.94 6.95 7.15 7.30 7.81

Table 11.

m t dd m m t

1 1 1

S

t t dd dd d d d s S

dd S S

S

dd d d S

Proton-proton -

A,A'

91'92 2' "3 93 '94 94895 ' 5 "6a '6aP96e

(br)

1 1 1 6 1 1 1 1 1 . 1 1 1 1 2 2 1 1 1 1 1 1

assignment (protons at carbon number) 3 92 2 94 95 93

coupling constants for teniposide.

coupled protons

1,2 2,3 3,4 3,11 3,ll' 11,ll'

number of protons

J (HZ) 5.3 13.8 3.2 8.1 10.5 10.6 - 1 7.8 8.5 8.5 8.1 10.1 10.1 4.8

3::ae

3.3

t4,t5

5.0

0ch3 96a 11' g6e 11 1 91 4 OH 97

A

2',6' 8 5 t4 :3

4'-0h

585

TENIPOSIDE

Table 111.

13C NMR assignments f o r teniposide.

chemical shift 6 (p.p.m.1 37.1 40.5 43.1 55.8 65.5 67.3 68.0 71.9 72.5 74.1 80.2 97.8 100.8 107.8 109.1 109.9 125.4 125.8 127.5 129.9 132.6 133.9 139.3 146.3 147.9 174.9

assignment (carbon number) 1 3 2 OCH 95 4 96 11 93 92 94 gl A, 97 2', 6' 8 5 t5 t3 4' t4 8' ' 4' ' t2 3', 5 ' , 6, 7 1' 13

J . JANTINA KETTENES-VAN DEN BOSCH ETAL.

586

4.5.

Mass Spectrum

The electron impact mass spectrum (EI-MS) of teniposide (Figure 6) was measured with a Kratos MS-80 mass spectrometer. The sample was introduced into the ion source (250 "C) by a direct inlet probe. An electron energy of 70 ev and an ionizing current of 100 W were used. The base peak in the spectrum is the ion at m/e 382. This fragment results from the loss of OH and the glucopyranosyl moiety (structure b, Scheme 11). The fragment corresponding to the loss of only the glucopyranosyl moietyI at m/e 400 (structure a), has a relatively low abundance (3-5%). An other fragmentation pathway is the formation of a fragment at m/e 154 corresponding to structure c. Minor fragmentation pathways are the formation of fragments at m/e 246 (structure d) and 201 (structure el, both pathways starting from mass 400 (a) [6l. 4.6.

Melting Range

The reported melting ranges are: Teniposide crystallized from ethanol : 246-255OC [51. Teniposide as obtained from the manufacturer: 237OC, with decomposition C6 I. 4.7.

Differential Scanning Calorimetry

The DSC thermogram for teniposide (Figure 7) was recorded with a Setaram DSC-111, with a scan rate of 3 K/min. The sample size was about 2 mg. The DSC thermogram was recorded in a closed vessel. Endothermic peaks appear at approximately 194 and 2180CI the integrated endothermic effect being 50.4 J/g. The strong exothermic peak has its maximum at 235"C, and possibly results from decomposition. When the vessel is 100-

O/o SO

-

587

TENIPOSIDE

r

OH

OCH3 OH m / e 400 (a)

OH

m l e 1 5 4 (c)

1

r

m l e 382 (b)

1

0 m l e 246 (d)

m l e 201 (e)

Scheme 11. Fragmentation pathways of teniposide.

J. JANTINA KETTENES-VAN DEN BOSCH ETAL.

588

cooled down and heated a second time, neither an endothermic nor an exothermic effect is observed, indicating that the material has changed. 4.8.

Optical Rotation

The optical rotation Lag1 of teniposide crystallized from ethanol ( c = 0,5 g/v, CHC13/MeOH, 9:1) was -108.6' [Sl. 4.9.

Dissociation Constant

The pK of the C4' phenolic functi n was determined spectrometrichly. Spectra of 0.8 x 10-8 M solutions of teniposide in 0.05 M sodium borate buffers containing 5% DMSO (v/v) were recorded with a Shimadzu W-200 double beam spectrometer. The ionic strength was kept at 0.15 M by addition of KC1. From the inflexion in the plot of the absorbance as a function of pH, a pKa of 10.13 was found [8].

9600 h

u?

z

7200

Y

3

-0 .c

a 4800 a) c 4-

2400

0 ,

Figure 7.

I

I

I

I

The DSC thermogram of teniposide (exothermic process).

TENIPOSIDE

4.10.

589

Electrochemistry Teniposide contains a 2,6-dimethoxyphenol group (ring

E) , which can be oxidized chemically or electrochemically.

The oxidation mechanism of teniposide was studied in aqueous solutions buffered at different pH values. The cyclic voltammogram of teniposide at pH 7.0 is presented in Figure 8 C8l.

The electrochemical oxidation of teniposide in aqueous solutions shows an overall transfer of two electrons. At pH values below 2.5, the oxidation proceeds in one voltammetric, pH-independent oxidation step (1, Figure 9). At pH values above 2.5, the oxidation proceeds in two voltammetric oxidation steps. The transfer of the first electron ( 3 , Figure 9) is reversible and is preceded by a proton transfer (2, Figure 9). The transfer of the second electron ( 4 ) results in the formation of an unstable cation which is converted rapidly into the 2-quinone of teniposide (5).

- 10

0

+ 5

+ 10

I

1000

I

I

800

I

I

600

I

I

400

I

I

+zoo

I

I

0

I

I

-200

E ( mV)

Figure 8 . Cyclic voltammogram of 0.125 mM teniposide in 0.1 M phosphate buffer pH 7.0 at a glassy carbon electrode. Scan rate 0.1 V/s. The cyclic voltammogram was recorded from -0.2 V to +1.1 V and back +0.2 V.


590

4 R

HjCO

OH

+2e+H+

(1)

OCH,

R

R

H3C0

OCH,

HjCO

OH

$l

+

H+

OCHj

0R

I

H,CO

+e

(3)

+e

(4)

+CHaOH

(5)

OCHj

0. R

H,CO

Q 0.

OCH,

HjCO

0

0 R

Q+2H++2e 0

H3CO

0

Figure 9.

i 111'

H3C0

OH OH

Oxidation mechanism of teniposide.

591

TENIPOSIDE

The o-quinone is adsorbed at the electrode surface, and is reduced in the cathodic scan (i ) to the corresponding I11oxidized in the second hydroquinone. The hydroquinone is 1. Both the oxidation of the hydroquinone anodic scan (i 111' and the reduction of the 2-quinone are pH-dependent [S].

5.

METHODS OF ANALYSIS

5.1.

Thin Layer and Paper Chromatography

Information on thin layer chromatographic systems and on paper chromatography is scanty. Only a few systems (Table IV) have been described C9l. Table IV. Thin layer and paper chromatography of teniposide. ~~

phase

solvent (v/v)

Rf

s ilicage1

chloroform methanol (21:l)

7

butanol-glacial acetic acidwater (3:l:l)

?

butanol-glacial acetic acidwater (3:l:l)

?

cellulose paper

5.2.

High Performance Liquid Chromatography

Table V presents a few liquid chromatographic methods used for the determination of teniposide in solutions. The unpublished method is used for the determination of the stability of teniposide and was shown to be stability-indicating (see section 6.2). However, the reversed phase chromatography methods published until now were mainly developed for the analysis of teniposide in biological materials (section 8 , Table VI).

J . JANTINA KE"E?S-VAN

592

DEN BOSCH ETAL.

Table V. High performance liquid chromatography of teniposide. column

mobile phase

Lichrosorb Rp18 methanol/20 mM (300~3.9nun) phosphate buffer 10 Frm PH 7 55/45 w/w Novapak Phenyl (75x3.9 mm) 4 llm

detection dynamic voltammetric detect ion

methanol/lO mM ECD + 500 mV phosphate buffer vs. Ag/AqCl pH 7.0 (55/45 w/w)

6.

STABILITY AND DEGRADATION

6.1

Stability in Aqueous Solutions

reference 10

not published

As etoposide , teniposide possesses a strained h a n 4 lactone ring (Figure 10). This Aku1.4 lactone ring is subject to degradation in both acidic and alkaline media. The degradation of teniposide has been studied in less detail than that of etoposide [ll]. However, it is assumed that the degradation reactions are essentially the same. In acidic media the glucopyranosyl moiety is cleaved, yielding 4'demethylepipodophyllotoxin (the aglycon) (I, Figure 10). The aglycon degrades further to the h a m hydroxy acid of 4'demethylepipodophyllotoxin (11). At pH values '5, the degradation of tenipoSi.de occurs through epimerization of the hm.b-fused lactone ring to the &-fused lactone (111). Further degradation results in the formation of the &-hydroxy acid (IV). Conversion of the ,Or.and lactone ring into the cid lactone ring (teniposide +. 111) at pH > 4 occurs through enolization and subsequent conversion of the enol(V) into ci6 -teniposide (111). The last-mentioned reaction requires proton transfers, which are facilitated by bases such as OH , H20, or anions of the acid used as a buffer.

6.2.

Stability in Plasma

Possible chemical instability of teniposide could cause problems in bioanalysis. Therefore, the stability of

TENIPOSIDE

593

R

0

OH

I

1

II

OH

R

0

0-R

I

I

0-R

0-R

IV

Figure 10.

Degradation pathways of teniposide in acidic and alkaline media (R = glucopyranosyl)

.

teniposide in plasma was studied at 37, 4, and -18OC. A stability-indicating assay was used allowing quantification of teniposide, &5-teniposide and 4'-dernethylepipodophyllotoxin, after isolation from biological matrices [6]. (See Table V, unpublished results). When teniposide in plasma is stored at 37"C, a decrease in the concentration is observed after 12 hours. This decrease is caused either by chemical degradation or is due to adsorption to precipitated protein. When plasma samples containing teniposide are stored at 4OC or -18"C, no decrease in the concentration was observed for at least 8 weeks. These studies allow the conclusion that it is not necessary to freeze plasma samples immediately after preparation.

7.

PHARMACOLOGY

7.1.

Mechanism of Action

Teniposide differs in its biological action from its parent podophyllotoxin, which is a spindle poison. Teniposide does not interact with the microtubule assembly [12,13], but prevents cells from entering mitosis. In contrast, the precursor podophyllotoxin arrests cells in the metaphase. Teniposide accumulates cells in the G2 phase.


594

Cells treated with teniposide show a rapid decrease of the mitotic index, with a simultaneous reduction of cell proliferation. Teniposide has been shown to induce double strand breaks and single strand breaks in DNA in intact cells and in nuclei, but not in purified DNA. The DNA degradation is dose- and temperature-dependent, and reversible after removal of the drug C12-151. Teniposide is believed to be activated in the cell nucleus by oxidation of the phenolic group to reactive intermediates C161. Interaction of these intermediates with DNA could also result in DNA damage. Studies indicate #at type I1 topoisomerase is probably the intracellular target in the DNA strand-breaking property of teniposide C16-19 ]. Teniposide inhibits the cellular uptake of thymidine, uridine, adenosine, and guanosine C141. The binding of teniposide to cell constituents is seven to ten times as high as that of etoposide [20], and as a result, the uptake of teniposide in the cell is ten times higher. Teniposide proved to be more active in the L1210 system than etoposide [15]. 7.2.

Pharmacokinetics

Up to now, teniposide is only administered intravenously. The pharmacokinetics of teniposide after intravenous infusion is described by an open two-compartment model C21-261 or by an open three-compartment model C9,271. No difference is observed in the disposition of teniposide administered at low or at high doses C27,281. The elimination half-life time after intravenous administration is about 10 hours [28], which is about two times longer than is found for etoposide. Figure 11 presents possible metabolic pathways of teniposide. Although teniposide is mainly cleared from the body by metabolic activity, ltttle information is available. Most of the metabolic studies on the epipodophyllotoxins have been performed with etoposide, a congener of teniposide. Pathway A: Small amounts of Cib-teniposide have been detected in urine and plasma by reversed phase chromatographic methods. I n V&O, this conversion is more pronounced at elevated temperatures and at higher pH values [25,311. Pathway B: The formation of the Cib or firrtnb-hydroxy acid of teniposide is probably a minor metabolic pathway.

TENIPOSIDE

595

on

OR

Figure 11. Possible metabolism of teniposide (R=glucopyranosyl)

.

Only one research group found an indication for the presence of this metabolite in urine C311. Pathway C and D: Up to now, these pathways were found to be important for etoposide only. Pathway E: An indication for relatively large amounts of conjugated (glucuronidated) 4'-demethylepipodophyllotoxin was found in patients [211 receiving teniposide, on prolonged intravenous infusion. However, the identity o f this metabolite was not confirmed by, e.g., mass spectrometry or NMR. 7.3.

Clinical Activity

Information on the clinical pharmacology was reviewed by O'Dryer et al. [l]. Teniposide is active against leukaemias, lymphoma, and neuroblastoma.


596

7.4.

Clinical Toxicity

The dose-limiting toxicity of tenipoSi.de was shown to be dose-related myelosuppression. Another toxic effect is hypotension, which is associated with rapid infusion of the drug. Other minor adverse reactions are vomiting and alopecia C11.

8.

ANALYSIS OF TENIPOSIDE MATRICES

8.1.

Teniposide

AND

METABOLITES IN BIOLOGICAL

The first pharmacokinetic fnd metabolic studies with teniposide were performed with a H-labelled drug [9,291. In these studies, the parent compound was separated from nonextractable metabolites and from the biological matrices by extraction with chloroform C9,291. The purity was checked by means of a TLC system [section 5.11. Apart from the HPLC methods, a radioimmunoassay for teniposide was developed. The sensitivity of this method proved to be comparable to an HPLC method C301. The method is not specific for the parent compound: cross reactions with etoposide, metabolites, and degradation products are observed. The methods published for the bioanalysis of teniposide are carried out with reversed phase HPLC. Table VI summarizes the reversed phase liquid chromatographic methods for the analysis of teniposide in biological fluids. The methods mentioned in this table are also suitable for the analysis of etoposide. The published methods are mostly dealing with the analysis of plasma; a few are also used for the analysis in urine and cerebrospinal fluid (CSF). Teniposide is mainly isolated by extraction with an organic solvent prior to the HPLC analysis. Ethyl acetate C311, chloroform [6,32,33,341, and 1,2-dichloroethane [6l are used. A few methods apply column extraction [35,36], allowing rapid analysis of the drug. The described extraction methods are likely to be also suitable for the analysis of the neutral metabolites 4 ' -demethylepipodophyllotoxin and cib-teniposide Two chromatographic systems have been reported for the separation of cib- and ;t)rand-teniposide [6 ,311.

.

TENIPOSIDE

591

Table VI. Published HPLC methods for the analysis of teniposide in biological fluids. matrix

sample pretreatment

column

plasma

chloroform extraction chloroform, extraction

Bondapak 10 pn c18’ Bondapak C18, 10 pn

e t h y l acetate extraction after addition o f NH412S04 preconcentration on PRP.1, postcolumn e x t r a c t i o n w i t h 1,2-dichloroethane 1,2-di c h l oroethane extraction

Ebndapak Phenyl, 10 pn

Ebndapak Phenyl 10 pn

+ 0.50 V vs.

solid-phase extract i o n C-18 Bond E l u t chloroform extraction

ODs Hypersil 5m

Ag/AgCl ECO + 0.9 v

i n j e c t i o n o f plasma after addition of 10% SDS

Chromspher

plasma

urine plasma CSF plasma urine

plasma

p l a sma plasma urine plasma

plasma

i n j e c t i o n o f plasma after addition of 10% SDS; o n - l i n e pre-column extraction

* ECD = electrochemical

detection

Lichrosorb RP 18, 10 pn

,

Lichrosorb RP 18, 10 pn

5 P Chromspher C 18 40 pn precolumn (4OOC) Bondapak Phenyl 10 pn w i t h Chromspher C 18 40 pn precolumn

detection

uv

determi- reference nation limit 500 ng/mT 32

254 nm fluores50 ng/ml cence 215/328 nm ECW 20 ng/ml + 0.85 V vs. Ag/AgCl

33

31

fluores8 ng/ml cence 30 ng/ml 230/328 m

35

5 ng/ml

6

500 ng/ml

36

50 ng/ml 280 nm 70 ng/ml 254 nm ECD 500 ng + 0.65 V vs. Ag/AgCl

34

10 ng/ml ECD 0.50 V vs. Ag/AgC1

39

ECD

uv

38

,

,

,

+


598

Recently, a flow injection method (FIA) was developed for the determination of teniposide in plasma. In this method, teniposide is converted by on-line electrochemical oxidation into the 2-quinone. Detection takes place at 365 nm which enables the determination of 1 pg teniposide per ml plasma. Prior to injection, teniposide is extracted with 1,2-dichloroethane C371. A method using micellar chromatography [381 was developed recently. This method allows the direct injection of (20 111) plasma samples. A detection limit of 0.5 v g / m l is obtained. In a second method with micelles, sodium dodecyl sulfate (SDS) is added to plasma prior to pre-column extraction; the extraction is followed by reversed phase liquid chromatography C391. The last-mentioned method has a detection limit of 10 ng per ml plasma. 8.2.

Teniposide Metabolites

No specific methods have been developed for the analysis of metabolites in urine or plasma. According to the proposed metabolic pathway (7.2.1, several metabolites are possible. These metabolites differ significantly in their physico-chemical properties. The metabolites with intact lactone rings can be separated by traditional reversed phase liquid chromatagraphy on a phenyl-bonded phase after liquidliquid extraction. For the chromatography of hydrophilic metabolites, %, hydroxy acids and glucuronides, a different approach 1s necessary.

ACKNOWLEDGEMENT The authors are grateful to Mr. D. Seykens, Department of Organic Chemistry, University of Utrecht, The NethfSlands for running the NMR spectra and providing relevant C reference data.

TENIPOSIDE

599

REFERENCES 1. O'Dwyer,

P.J., Alonso, M.T., Leyland-Jones, B., and Marsoni, S. (1984). Cancer Treatment Report 68, 1455. Kelly, M., and Hartwell, J. (1954). J. Nat.Cancer Inst.

14, 967. Kuhn, M.,

and Von Wartburg, A. (1969). Helv. Chim. Acta

52, 948. -

8. 9 10 11 12 13 14 15 16

Kuhn, M., Keller-JuslBn, C., and Von Wartburg, A. (1969). Helv. Chim. Acta 52, 944. Keller-Juslgn, C., Kuhn M., and Von Wartburg, A. (1971). J. Med. Chem. 14, 936. Holthuis, J.J.M. (1985). Ph.D. Thesis, University of Utrecht, The Netherlands. Holthuis, J.J.M., Kettenes-van den Bosch, J.J., and Bult, A. Etoposide. To be published in: Analytical Profiles on Drug Substances. Vol. 18. Holthuis, J.J.M., Vendriq, D.E.M.M., Van Oort, W.J., Zuman, P. (1987). J. Electroanal. Chem. Interfacial Electrochem. 220 101. Creaven, P.J. and Allen, L.M. (1975). Clin Pharmacol. and Ther. 18,226. Ploegmakers, H.H.J.L., Mertens, M.J.M., Van Oort, W.J. (1985). Anal. Chim. Acta 174, 71. Beijnen, J.H., Holthuis, J.J.M., Kerkdijk, H.G., Van der Houwen, O.A.G.J., Paahan, A.C.A., Bult, A., and Underberg, W.J.M. (1988). Int. J. Pharm. 41, 169. Brewer, C.F., Loike, J.D., and Horwitz, S.B. (1979). J. Med. Chem. 22, 215. Loike, J.D. and Horwitz, S.B. (1976). Biochem. 15, 5435. Horwitz, S.B. and Loike, J.D. (1977). Lloydia 40, 82. Long, B.H., Musial, S.T., and Brattain, M.C. (1984). Biochemistry 23, 1183. Yang, L., Rowe, T.C., and Liu, L.F. (1985). Cancer Res.

45, 5872. 17 Z e n , G.L., Yang Liu, Rowe, T.C., Halligan, B.D., Tewey, K.M., and Liu, L.F. (1984). J. Biol. Chem. 259, 13560. 18 Rowe, T., Kupfer, G., and Ross, W. ( 1 9 m . Biochem. Pharmacol. 34, 2483. 19 Dorr, R.T., Liddil, J.D., and Gerner, E.W. (1986). Cancer Res. 46, 3891. 20 Allen, J. (1978) Drug Metab. Rev. 8, 119. 21 Rossi, C., Zucchetti, M., Sessa, C., Urso, R. Mangioni, C., and D'Incalci, M. (1984). Cancer Chemother. Pharmacol.1 13, 211. 22 D'Incalci, M., Rossi, C., Sessa, C., Urso, R., Zucchetti, M. Farina, P., and Mangioni, C. (1985). Cancer Treat. Rep. 69, 73.

600

J. JANTINA KETTENES-VANDEN BOSCH ETAL.

23 Canal. P., Bugat, R., Michel, C., Roche, H. , Soula, G., Combes, P.F. (1985). Cancer Chemother. Pharmacol. 15, 149. 24 Stewart, D.J., Richard, M.T., Hugenholz, H., Dennery, J., Nundy, D., Prior, J., Montpetit, V., Hopkins, H.S., et al. (19841, J. Neuro-Oncol. 324, 315. 25 Postmus, P.E., Holthuis, J.J.M. , Haaxma-Reiche, H., Mulder, N.H., Vencken, L.M., Van O o r t , W.J., Sleijfer, D.Th., and Sluiter, H.J. (1984). J. Clin. Oncol. 2, 215. 26 Evans, W.E., Sinkule, J.A., Crom, W.R., DOW, L., Look, A.T., and Rivera, G. (1982). Cancer Chemother. Pharmacol. 7, 147. 27 Eolthuis, J.J.M., De Vries, E.G.E., Postmus, P.E. , Van Oort, W.J., Verleun, H., Hulshoff, A., Sleijfer, D.Th, Mulder, N.H. (19871, Cancer Treatment Rep. 2, 599. 28 Holthuis, J.J.M. (1988). Pharm. Weekbl. Sci. Ed. 10, 101. 29 Allen, L.M. and Creaven, P.J. (1975). Europ.. J Canc. Clin. Oncol. 11,679. Kannellopoulos, K.S., Brown, N.S., Issell, 30 Ho, D.H., B.F., and Bodey, G.F. (1985). J. Immunol. Methods. g ,5. 31 Sinkule, J.A., and Evans, W.E. (1984). J. Pharm. Sci. 73, 164. 32 Strife, R.J., Jardine, I., and Colvin, M. (19801, J. Chromatogr. 182, 211. 33 Strife, R.J., Jardine, I., and Colvin, M. (1981), J. Chromatogr. 224, 168. 34 Holthuis, J.J.M., Van Oort, W.J., and Pinedo, H.M. (1981). Anal. Chim. Acta 130, 23. 35 Werkhoven-Goewie, C.E., Brinkman, U.A.Th.I Frei, R.W., De miter, C., and De Vries, J. (1983). J. Chromatogr. 276, 349. 36 Rideout, J.M., Ayres, D.C., Lim, C.K., and Peters, T.J. (1984). J. Pharm. Biomed. Anal. 2, 125. 37 Van Opstal, M.A.J., Blauw, J.S., Holthuis, J.J.M., Van Bennekom, W.P., and Bult, A. (1987). Anal. Chim. Acta 202, 35. 38 Van der Horst, F.A.L. (1989), Ph.D. Thesis, University of Utrecht, The Netherlands. 39 Van Opstal, M.A.J., Van der Horst, F.A.L., Holthuis, J.J.M., Van Bennekom, k . P . , and Bult, A. (1989) J. Chromatogr., 495, 139.

-

-

Terbutaliae Sulfate

Satinder Ahuja 2nd J. Ashman Develapment Department Pharmaceuticals Sivisipn Ciby-Geigy Corp., Suffern, W 10901

ANAL\llCAL PROFLES OF DRUG SUBSTANCES VOLUME 19

601

Copyright 0 1990 by Academic Press. Inc. All rights of reproductionin any form reserved.

SATINDER AHUJA AND J. ASHMAN

602

Terbutaline Sulfate S . Ahuja and J. Ashman Development Department Pharmaceuticals Division Ciba-Geigy Corp., Suffern, NY 10901

1.

Description 1.1 Introduction 1.2 Formula, Name, Formula Weight 1.3 Appearance, Color, Odor

2.

Physical Properties 2.1 Ultraviolet Spectroscopy 2.2 Infrared Spectroscopy 2.3 Nuclear Magnetic Resonance Spectroscopy 2.4 Mass Spectrometry 2.5 Circular Dichroism 2.6 Differential Scanning Colorimetry 2.7 Melting Range 2.8 Thermogravimetry 2.9 X-ray Powder Diffraction 2.10 Dissociation Constant 2.11 Solubility 2.12 Water Absorption 2.13 Distribution Coefficient

3.

Synthesis

4.

Stability 4.1 Solid State Stability 4.2 Solution Stability

5.

Pharmacokinetics, Metabolism and Activity 5.1 Absorption/Excretion/Elimination 5.2 Drug Binding 5.3 Pharmacodynamics 5.4 Activity of Enantiomers

6.

Analytical Methodology 6.1 Titrimetry 6.2 Gas chromatography 6.3 High pressure Liquid Chromatography 6.4 Thin Layer Chromatography 6.5 Colorimetry 6.6 Mass Fragmentography

7.

Toxicological Studies References

TERBUTALINE SULFATE

603

Terbutaline Sulfate

1.

Description 1.1

Introduction Terbutaline sulfate is a synthetic fl2-adrenoceptor that is used as a bronchodilator in the treatment o f bronchial asthma.

1.2 Formula, Name, Formula Weight

r

1

Terbutaline Sulfate Formula Weight:

548.658

c24H40N2010s

Terbutaline sulfate has been described by the following chemical names: (i)

5-[2-[(1,l-Dimethylethyl)amino]-1-hydroxyethyl]-1,3-benzenediol sulfate (2:l salt)

(ii)

CY- [ (tert-Butylamino)methyl] -3,5-dihydroxybenzyl alcohol sulfate (2:l salt)

(iii) 1-(3,5-Dihydroxypheny1)-2-(~-butylamino)ethanol sulfate (2:l salt) 1.3 Appearance, Color, Odor Terbutaline sulfate is a white to gray-white crystalline powder, odorless or with a faint odor of acetic acid.

2.


Ultraviolet Spectroscopy The ultraviolet absorption spectrum of terbutaline sulfate in 0.1N hydrochloric acid (Figure 1)

I -

1.0

1

PEAK-FIHI

0.90

L

m-0.6745

-

0.80

0.70

am W

2

#m,

0.50 0.40

0.30 0.20

0.10

0.0 0

N -a

0 N Ln

E

E

2

0

m N

0

P

WAVELENGTH (ra)

Figure 1

U l t r a v i o l e t Spectrum of Terbutaline S u l f a t e (S-4-90-4) i n 0 . 1

HC1

TERBUTALINE SULFATE

605

exhibits a Amax at 276nm and yields an A(l%,lcm) value of 67.6. This absorption arises from the transition of the electrons in the phenyl ring (aromatic) (1).

2.2 Infrared Spectroscopy The infrared absorption spectrum of terbutaline sulfate in a KBr pellet (Figure 2) exhibits the following bands which are consistent with its structure (1) : Wavenumber (cm-l)

3330 3050 2970 2920 2720-2900,2660,2500 1610,1485 1455 1400,1380 1240,1210 1200 1065 850, 690

Assignment

OH stretch aromatic CH stretch methyl asymmetric stretch methylene asymmetric stretch secondary amine salt stretch aromatic ring stretch methylene scissoring/asymmetric bend t-butyl symmetric bend t-butyl characteristic absorbances phenolic C - 0 stretch secondary alcohol C-0 stretch 1,3,5 trisubstituted benzene, out-of-plane bend

2.3 Nuclear Magnetic Resonance Spectroscopy The NMR spectrum of terbutaline sulfate in deuterium oxide (Figure 3) is consistent with its structure (1) :

Figure 2

Infrared Spectrum of Terbutaline Sulfate (S-4-90-4)

Figure 3

NMR Spectrum of Terbutaline Sulfate (S-4-90-4) in D20


608

Chemica1 Shift (PPd

Multiplicity Singlet

1.45

Relative Integral of Protons

Ass igment

9

Methyl Protons

3.4

Triplet

2

Methylene Protons

4.7

-

5.1

Mu1tiplet

---

Methine Proton Exchangeables

6.35

-

6.7

Multiplet

3

Aromatic Protons

3.1

2.4

+

Mass Spectrometry The mass spectrum (Figure 4 ) is compatible with the indicated structure of terbutaline sulfate and shows the following fragmentation pattern ( 1 ) . m/e -

Structure

225

M+

210

M-CH3

207

M-HzO

192

M- (CHa+HzO) HO

150

Ho

H

Ho

139 Ho

OH

TERBUTALINE SULFATE

160

609

7

90

80

-

70

60

-

50

-

40

30

20

ie

Figure 4

Mass Spectrum of Terbutaline Sulfate (CDF 2037)


610

111

139-CO tB

86

H2CzN-C(CH3) 3

HH

70

57 CH3

2.5 Circular Dichroism Commercially sold terbutaline sulfate is racemic; no circular dichroism is observed.

2.6 Differential Scanning Calorimetry No reliable purity value can be determined since terbutaline sulfate melts with decomposition.

2.7 Melting Range noted above, terbutaline sulfate decomposes upon melting. Melting points determined by DSC for batches of terbutaline sulfate identified as crystal form A range from 264OC to 271OC. For batches identified as crystal form B, these values range from 258OC to 26OOC (1).

As

TERBUTALINE SULFATE

611

2.8 Thermogravimetry

Thermogravimetric analysis generally gives a weight loss of less than 0.5% between RT and 22OOC (1). 2.9 X-ray Powder Diffraction

Two crystal forms have been characterized by x-ray powder diffraction patterns (1). The A form shows lines at 8.5, 9.4, 10.2, 11.9, 13.0, 15.2, 16.8, 17.3, 18.0, 19.6, 21.2, 22.0, 22.6, 24.1, 26.0 and 27.0 degrees 28. The B form shows lines at 6.9, 8.1, 9 . 2 , 10.6, 12.4, 13.1, 13.9, 16.1, 16.6, 17.9, 18.6, 19.0, 19.8, 21.0, 23.2, 24.3, 25.4 and 27.2 degrees 20 (Figure 5). 2.10 Dissociation Constant

The following pKa values have been reported for terbutaline sulfate: 8.8, 10.1 and 11.2. The 10.1 value can be assigned to the amino group. The other two pKa values (8.8 and 11.2) may be attributed to the aromatic hydroxyl groups of this compound. (1) 2.11 Solubility

The equilibrium solubility values in various solvents, at 25OC, are given in Table I (1). TABLE I Solubility of Terbutaline Sulfate Solvent

mg/d

Water

>20

0.1lj HC1

>20

20'1E 91'0E S0'62

96'92 b2'SZ Sb'bZ

06'22 t1'22 €1.12 16'61

sew 6L'LT

L2'91 b0'tI

62'81

9b'tI €2'81 LE'6 22.8 86'9

-= --

-=

-= ----

I

I

0

44

u

TERB UTALINE SULFATE

613

Table I Solubility of Terbutaline Sulfate (cont ' d ) 0.1N - NaOH

>20

Ethanol

1.2

10% Ethanol

>20

Methano1

2.7

2.12 Water Absorption

A

0.2% gain in water content has been observed with the samples stored at 25OC/75% R.H. for 14 days.

2.13 Distribution Coefficient

Distribution coefficients in various organic phases vs. aqueous phase at room temperature are given in Table I1 (1).

TABLE I1 Distribution Coefficients of Terbutaline Sulfate Organic Phase

Aqueous Phase

C K = org . 'aq.

Chloroform

0.1N - HC1

0.0

Ether

0.1N - HC1

0.0

Isooctane

0.1N - HC1

0.0

Chloroform

0.1N - NaOH

0.0

614

3.


Synthesis The synthesis for terbutaline sulfate given below is based on a U.S. patent issued to Wetterlin, et a1 (2).

I

1

I

4.

Stability

4.1 Solid State Stability Terbutaline sulfate is a stable compound under normal storage conditions. No change in chromatographic impurities was detected after three years storage at room temperature (1).

TERBUTALINE SULFATE

4.2

Solution Stability Discoloration of aqueous solutions of terbutaline sulfate is caused by oxidation of terbutaline and is enhanced by low pH and by ultratrace levels (ppb) of metals in the presence of oxygen. HPLC analysis of degraded terbutaline sulfate solutions suggest that oxidative degradation is favored __ (3,4).

5.

Pharmacokinetics, Metabolism and A tivity Distribution data (Section 2.13) suggests terbutaline sulfate is hydrophilic. 5.1 Absorption/Excretion/Elimination The structure of terbutaline sulfate prevents it from being metabolized by catechol-0-methyl transThe principle ferase or monoamine oxidase (5,6). pathway of metabolism is conjugation with sulfuric

615

616


acid or gulcuronic acid. However, there are species differences and the extent of metabolism depends on the route of administration. Following oral administration, approximately 50% of the dose is excreted unchanged in the feces. In a 24 hour collection period, 5.7% of the dose was recovered unchanged in the urine, while 16.8% was recovered as conjugated terbutaline. In a 72 hour collection period 92% of the dose was recovered with 52% in the feces and 6% in the urine as unchanged terbutaline (5). Oral absorption capacity ranges have been estimated with a range of 25-80%, this creates a range in the extent of bioavailability of 7-26%, the decrease in the percentages being due to a high first pass metabolism . The terminal half-life in healthy subjects is approximately 17 hours (7). The biological half-life is 3.6 hours (8). Although absorption from the gastrointestinal tract is incomplete, peak plasma levels of unchanged terbutaline reach approximately 5 ng/mL (8,9), which apparently is sufficient to produce effective changes in pulmonary function. The pattern of metabolism following oral inhalation of terbutaline from a metered dose dispenser is similar to the pattern observed following oral ingestion. This is probably because approximately 90 percent of the inhaled does is swallowed (10,ll). The patterns of metabolism and excretion following intravenous and subcutaneous administration are essentially identical. Only 2 percent of the drug can be recovered in the feces following parenteral administration (6,9). A significant amount of unchanged terbutaline is excreted in the urine following intravenous or subcutaneous administration. Approximately 60 percent of the administered

TERBUTALINE SULFATE

dose is recovered as unchanged terbutaline in the urine (6,12). The presence of an unidentified metabolite in the urine, which represented approximately 15 percent of the administered dose, was reported by Davies _ et _ a1 (6). The high percentage of conjugated terbutaline following oral administration suggest significant sulfate conjugation took place in the gut wall or during the first pass through the liver. After a single intravenous dose, plasma concentrations of terbutaline decline in a multi-exponential fashion (13). The terminal half-life is roughly 17 hours with a two-fold variation between subjects. Intravenously administered terbutaline is excreted mainly in the urine with approximately 60% being recovered as the unchanged drug and between 4 and 19% being recovered as the sulfate conjugate. No other metabolites have been identified. Estimates for total body clearance range from 165 to 170 mL/min. Volumes of distribution at steady-state range from 83 to 140 L. No statistically significant difference was observed between the serum concentration time profiles for the subcutaneous dose in the healthy volunteer and patient groups. Serum concentrations increased to achieve a peak concentration o f 7.2 ( 2 1.7) ng/mL at 0 . 4 3 (f 0.13) hours after dosing. As in the case of the healthy volunteers the subsequent decline from the peak was biphasic. The availability of the drug after oral dosing ranged from 7.0 to 14.0% (mean It S.D. = 10.0 f 3.0%) in the 8 asthmatic patients.

In a series of pharmacokinetics studies after oral and intravenous administration of tritiumlabelled drug, unchanged terbutaline accounted for less than 15% of the total radioactivity in plasma following oral administration (14). However, after acid-hydrolysis unchanged

617

618

SATINDER AHUJA AND 3. ASHMAN

terbutaline accounted for 90% of the radioactivity. In contrast, unchanged terbutaline accounted for more than 85% of the total radioactivity over the first 60 minutes after intravenous dosing. These results suggests extensive conjugation of terbutaline before the drug reaches the systemic circulation. The site of pre-systemic conjugation has not been established. The pharmacokinetics of terbutaline has been measured in two studies after oral and subcutaneous administration of the drug. Maximum concentrations of terbutaline (mean: 3.2 i: 0.4 ng/mL) were achieved at 2 - 4 hours after oral dosing. After subcutaneous dosing maximum levels of 6.9 k 0.5 ng/mL were observed at 30 minutes. Approximately 30% of the dose was excreted by glomerular filtration in 12 hours and 40% in 72 hours. No obvious differences were detected in the plasma concentration-time profiles for healthy volunteers and patients.

5.2 Drug Binding Terbutaline plasma protein binding is low, 14 25%. In contrast, binding to erythrocytes is more pronounced producing erythrocyte:plasma concentration ratios of 2.0 to 2.6. 5.3 Pharmacodynamics The relationships between plasma terbutaline concentrations after oral and subcutaneous dosing and pulmonary effects have been investigated in two studies involving 10 and 8 asthmatic patients, respectively. In both studies serum concentrations of the drug were correlated with the forced expiration volume in 1 second. Maximum pulmonary effects occurred at 30 - 60 minutes after the subcutaneous dose and at 2 - 4 hours after the oral

TERBUTALINE SULFATE

dose. These effects coincided with peak concentrations of terbutaline and c-AMP in plasma. No significant effects on heart rate and blood pressure were noted in one of the studies and the increases in tremor did not appear to parallel either the serum level or bronchodilating effect. Linear regression analysis of pulmonary responses in children with chronic childhood asthma also showed a statistically significant relationship between the plasma concentration of the drug and its effect on forced expiration volume in 1 second and peak expiratory flow rate (PEFR) within patients. Pharmacodynamic responses increased with ascending doses. In dogs, the metabolism does not depend on the Very little route of administration (6,15). sulfate conjugate was detected in the urine following intravenous, intraduodenal, or intragastric administration. In rats, the glucuronide conjugate appeared as the only urinary metabolite (15,16) and the amount of that metabolite formed was not influenced by the route of administration. 5.4

Activity of Enantiomers The (-) isomer of terbutaline has been found to be 200 times more potent than the (+) isomer for the f 3 ~ receptors (17).

6.

Analytical Methodology

6.1

Titrimetry Terbutaline sulfate active ingredient can be titrated in acetic acid:acetonitrile (1:l) with perchloric acid in acetic acid (18).

619


620

6.2

Gas Chromatography Terbutaline sulfate can be analyzed by gas chromatography by first converting the terbutaline to its tris-trimethyl silyl ether and then chromatographing on 3% OV-17 on an appropriate neutralized, silanized diatomaceous earth support. Column temperatures in the range of 15OoC to 190°C have been used. The derivatization scheme follows (19):

L"

-

1

1

6.3 High Pressure Liquid Chromatography

Terbutaline sulfate can be analyzed by reversedphase and by ion-pairing high pressure liquid chromatography. Several different systems have been used. Terbutaline sulfate in intravenous solutions has been analyzed by chromatographing on a pBondapak Cis column using a mobile phase consisting of 35% methanol (V/V) in an aqueous solution 0.35M in acetic acid and 0.005M in sodium heptanesulfonate (20). In blood, it has been analyzed by chromatographing on a pBondapak Cia column using a mobile phase consisting of 5% acetonitrile in a pH 4 . 0 sodium acetate buffer (21).

62 1

TERBUTALINE SULFATE

An automated method based on liquid chromatography

has been utilized for the determination of ter50 butaline in human plasma in the range of 5 pmo1e.d-l (22). The necessary sensitivity and selectivity was obtained by using electrochemical detection and a microprocessor-controlled column switching system. A combination o f three columns was used: a Ca type for pre-separation, a CIS type for trapping and, for final separation, a strongly acidic ion exchanger. The accuracy of the method was examined by comparison with a method based on gas chromatography - mass spectrometry. The overall precision was -+ 3.5% and ? 2.2%, respectively at 5 and 50 pmo1e.d-l. The total absolute recovery for terbutaline and internal standard at the above concentration levels were in the range 85 106%.

-

-

A liquid chromatographic method with electro-

chemical detection (LC-EC) has been found useful for the quantitative analysis of terbutaline in the range 5-50 pmole*mL-l of human plasma (23). Terbutaline is isolated from plasma on an ionexchange column and the eluate is concentrated on a hydrophobic precolumn on-line in the chromatographic system. The precolumn is then back-flushed for further separation onto a hydrophobic analytical column. The mobile phase is a methanol-aqueous buffer to which sodium perchlorate is added to achieve resolution from interfering peaks. A glassy carbon electrode is used for detection. Comparison has been made with gas chromatographymass spectrometry (GC-MS) to examine the accuracy of the method. A commercially available chiral stationary phase

containing al-acid glycoprotein on silica (EnantioPac, LKB) was used for the resolution of enantiomers of terbutaline (24). The mobile phase contained 0.003 M tetrapropyl-ammonium bromide adjusted to pH 7.0. Terbutaline enantiomers in


622

biological samples have been analyzed on a cyclodextrin column (25). Dosage forms of terbutaline sulfate have been analyzed by chromatographing on a pBondapak phenyl column using a mobile phase consisting of 8% methanol (V/V) in 0.02M pH 3 . 6 potassium phosphate buffer (26).

6.4. Thin Layer Chromatography Terbutaline sulfate has been chromatographed on a silica gel plate with a TLC system using a developing solvent consisting of isopropyl alcohol: cyc1ohexane:formic acid (13:5:1). Detection is accomplished by using 4-aminoanti-pyrine and potassium ferricyanide spray reagents (18). 6.5

Colorimetry A method based on the following reaction of ter-

butaline sulfate with 4-aminoantipyrine in the presence of potassium ferricyanide can be used for analysis of terbutaline sulfate dosage forms (18).

TERBUTALINE SULFATE

6.6

623

Mass Fragmentography

A simple and sensitive method for the determination of terbutaline in serum and urine has been developed (27). A mass spectrometer in the multiple ion

detection mode was used as a gas chromatographic detector. Levels were monitored after oral and subcutaneous administration of the drug. The sensitivity is 1 ng/mL using 1 mL of serum.

A mass fragmentographic method for determination of

terbutaline sulfate in biological fluids has been described ( 1 9 ) . The mixed TMS-TFA derivative is chromatographed and the m/e 355 ion is monitored. Measurement is possible to 0.3 ng/mL in human plasma. WS

I nrs - 0 2-

7.

Toxicological Studies Intravenous toxicological testing in male rats yields an LD50 of 48.41 mg/kg ? 1 . 6 3 (1).


624

References 1.

2. 3.

4. 5.

6.

7. 8. 9. 10.

11.

12. 13.

14. 15.

16. 17. 18. 19.

20.

S. Ahuja, Personal Communication, February, 1976. K. I. Wetterlin and L. A. Svensson, U.S. Patent 3, 937, 838, Feb. 10, 1976. L. A. Svensson, Acta Pharm. Suec., 9 , 141 (1972). S. Ahuja, P. Liu and J. Smith, 45M International Congress o f Pharmaceutical Sciences, Montreal, Canada, September 2-6, 1985. J. J. McPhillips, Pharmacol. Biochem. Prop. Drug Subst., 1, 311 (1977). 6. Davies, C. F. George, E. Blackwell, M. E. Conolly and C. T. Dollery, Br. J. Clin. Pharmacol., 1, 129 (1974). L. Nyberg, Eur. J. Respir. Dis. [Suppl], 134, 149 (1984). J. G. Leferink, W. VanDerBerg, I. Wagemaker-Engels, J. Kreukniet and R. A. Maes, Arzneimittelforschung, 2 (2)) 159 (1982). T. Nilsson, K. Persson and K. Tegner, Xenobiotica, 2, 363 (1972). E. W. Blackwell, R. H. Briant, M. E. Conolly, D. S. Davies and C. T. Dollery, Br. J. Pharmacol., 50, 587 (1974). H. T. Nilsson, B. G. Simonsson and B. Strom, Europ. J. Clin. Pharmacol. , lo, 1 (1976). T. Nilsson, K. Persson and K. Tegner, Xenobiotica, 2, 363 (1972). V. A. John, personal communication, December 16, 1988. D. S. Davies, Europ. J. Res. Dis., 65, 111 (1984). H. T. Nilsson, C. G. A. Persson, K. Persson, K. Tegner and A. Ryerfelt, Xenobiotica, 3 , 615 (1973). W. D. Conway, S. M. Singhvi, M. Gibaldi and R. N. Boyes, ibid, 3, 813 (1973). K. Wetterlin, J. Medicinal Chem., 15 (11)) 1182 (1972). USP XXI, p. 1019 , United States Phzmacopeial Convention, Rockville, MD, 1985. R. A. Clare, D. S. Davies ani T. A. Baillie, Biomed. Mass Spectrom. 6 (11, 31 (1979). D. A. Williams,E. Y. Y. Fung and D. W. Newton, J. Pharmaceutical Sciences, fl (8) , 956 (1982).

TERBUTALINE SULFATE

625

References (cont ’ d)

J. M. Pugely and 0. L. Frick, J. Allergy Clin. Immunol, p. 162, March 1978. 22. L . E. Edholm and B. M. Kennedy and S. Bergquist, Chromatographia, l6, 341 (1982). 23. S . Bergquist and L. E. Edholm, J. Liq. Chromatogr., 6, 21.

559 (1983). 24.

G. Schill, I. W. Wainer and S. A. Barkan, ibid,

9,

641

(1986). 25. A . Walhagen, 26.

L. E. Edholm, B-M. Kennedy and L. C. Xiao, Chirality, 1, 20 (1989). V . Das Gupta, J. Liquid Chromatography, 9 (5), 1065 (1986).

27.

J. G. Leferink, I. Wagemaker-Engles and R. A. A. Macs, J. Chromatogr., 143, 299 (1977).

TERFENADINE

ADNAN A . BADWAN The Jordanian Pharmaceutical ManufacturingCo. Ltd. Naor - Jordan

HANAN N. ALKAYSI Department of Medicinal Chemistry Faculty of Pharmacy Jordan University of Science and Technology lrbid -Jordan

LINA BAHOUTH OWAIS The Jordanian Pharmaceutical ManufacturingCo. Ltd. Naor - Jordan

MUTAZ SHEIKH SALEM Department of Pharmaceutical Technology Faculty of Pharmacy Jordan University of Science and Technology lrbid -Jordan

TAWFIQ A. ARAFAT Department of Pharmaceutical Chemistry Faculty of Pharmacy University of Jordan Amman -Jordan ANALYnCAL PROFILES OF DRUG SUBSTANCES VOLUME 19

621

Copyright 0 1990 by Academic Press. lnc. All rights of repduction in any form reserved.

ADNAN A. BADWAN ETAL.

628

CONTENTS

1

- DESCRIPTION 1.1. 1.1.1. 1.1.2. 1.1.3. 1.1.4. 1.2. 1.2.1. 1.2.2. 1.2.3. 1.3.

2

Nomenclature. Chemical Names. Generic Names. Registry Number. Wiswesser Line Notation. Formulae. Emperical Formula. Molecular Weight. Structural Formula. Colour, Appearance and Odour.

- SYNTHESIS

- POLYMORPHISM AND CRYSTAL HABITS 4 - PHYSICO-CHEMICAL PROPERTIES

3

4.1. 4.2. 4.3. 4.4. 4.5. 4.5.1. 4.5.2. 4.5.3. 4.5.4. 4.5.4.1. 4.5.4.2. 4.5.5. 4.5.5.1. 4.5.5.2. 4.5.6.

Melting Range. Differential Scanning Calorimetry Solubility. DissociationConstant. Spectral Properties. Ultraviolet Spectrum. FluorescenceSpectrum Infra-Red Spectra. Mass Spectra. Electron Impact. Chemical Ionization. Nuclear Magnetic Resonance. Proton Magnetic Resonance. Carbon 13. X-Ray Powder Diffraction.

TERFENADINE

5

629

- METHODS OF ANALYSIS Starting Material and PharmaceuticalDosage Forms. 5.1. 5.1.l . ElementalAnalysis. 5.1.2. Non-Aqueous Titration. 5.1.3. Spectrophotometric Methods. 5.1.3.1.Ultraviolet Absorption. 5.1.3.2. First Derivative. 5.1.3.3.Colourimetric Spectroscopy. 5.1.4. Chromatographic Methods. 5.1.4.1.Thin Layer Chromatography. 5.1.4.2. High Pressure Liquid Chromatography. a - Synthesis Impurities. b - Bulk and Dosage Forms. 5.2. Body Tissues and Fluids. 5.2.1. Radioimmunoassay. 5.2.2. 14CAnalysis. 5.2.3. Gas Chromatography-Mass Spectrometry.

6

- STABILITY 6.1. 6.2.

7

Stability of Solid. Stability in Solution.

- PHARMACOKINETICS 7.1. 7.2. 7.3. 7.4. 7.5. 7.6. 7.7.

Absorption. Bioavailability. Distribution. Protein Binding. Metabolism. Excretion. Half Life.

ADNAN A. BADWAN ETAL..

630

1. DESCRIPTION

1.1, Nomenclature 1.1.l.Chemical names

1.1.1.2

-

1.1.1.3

-

1.1.1.4

-

1.1.1.1

1-piperidinebutanol, alpha-[ 4- (1, 1-dimethyl ethyl)phenyl I -4(hydroxydiphenylmethyl)-. Alpha- [ &(l,l-dimethyl ethyl) phenyl ] 4- (hydroxy diphenyl methyl) 1-piperidine butanol. 1-(4(1, 1-dimethyl ethyl) phenyl 4- (4-hydroxydiphenyl) methyl piperidine) butan-1lo1 . 1(4-Tertbutyl phenyl) 4- 4- (a-hydroxybenzhydryl) piperidino butanol.

-

-

-

-

1.1.2. Generic name Terfenadine.

1.1.3. Registry number Chemical Abstract CAS number 50679-08-8.

1.1.4. Wiswesser line notation T6NIJ A3YQR DX1 of 1 and 1 and DXQR and R.

1.2. Formulae 1.2.1. Emperical formula

1.2.2. Molecular welght 471.69.

TERFENADINE

63 1

1.2.3. Structural formula

OH

1.3. Colour, Appearance and Odour. White, crystalline powder, odourless with very bitter taste.

2. SYNTHESIS

A mixture of a,a-diphenyl-4-piperidine methanol (I), 1- 4-(1,l -dimethyl ethyl) phenyl - 4-chloro- 1-butanone (II), potassium bicarbonateand potassium iodide in toluene was refluxed with stirring at room temperature. The warm reaction mixture was filtered and the cooled filtrate treated with excess ethereal hydrogen chloride. The resulting precipitate was recrystallizedtwice from a mixture of methanol/isopropanolto give 1- 44 1 , l -dimethyl ethyl) phenyl -4-4-(hydroxydiphenyI-methyl)-1-piperidinyl- 1-butanone hydrochloride (111). A solution of (Ill) in methanolwas treated with a solution of potassium hydroxide in methanol until it was basic. The resulting mixture was cooled, stirred and treated portionwise with potassium borohydride. The cooling bath was removedand the reaction was stirred and then concentratedon a steam bath at reduced pressure to give a solid residue. After washing with water and two recrystallizations from acetone, tetfenadine (IV) waspbtained (1).

Scheme (1) Synthetic Pathway of Terfenadine.

.

*

TERFENADINE

633

3. POLYMORPHISM AND CRYSTAL HABITS

It appears that terfenadine could exist in various polymorphic forms. At present three distinct polymorphic forms and two solvates were identified. These were obtained from recrystallization of terfenadine from different solvents. Polymorph I: obtained by recrystallization from ethanol-water mixture. Polymorph II was obtained by recrystallization from methanol. Polymorph II I (metastable) was obtained by recrystallization from propylene glycol.The differences in their physico-chemical properties are mentioned in the relevent subsequent sections. In commercial materials polymorph I and II coexist in different proportions. Polymorphic forms II and Illcould beconverted to polymorph I by boiling in water. The presence of crystallization inhibitors retarded such transformation. In addition, terfenadine glass form could be obtained by rapid cooling of the drug melt. Crystals obtained from commercial material were euhedral having bladed and circular shape crystals, while polymorph Ill has a thin flake type powder. In this monograph the measurements were carried out mainly on the most stable polymorph I as described in the following sections (2).

4. PHYSICO-CHEMICAL PROPERTIES

4.1. Melting Range

USP specifies that the melting range of terfenadine is between 145-151"C (3). However, terfenadine exhibits different polymorphic forms having the following melting ranges (2). Polymorph I (moststable) Polymorph II Polymorph Ill

149-152°C. 146-148°C. 142-144°C.

In addition, terfenadine melt forms glass upon cooling yielding glass transitions at 55.93", 57.91 O, 59.88"C(4).


634

4.2. DifferentialScanning Calorimetry

Thermograms of the terfenadine stable, metastable polymorphic and glass forms are shown in figure (1a and b). These thermograms were obtained using Mettler TA3000 DSCQO unit. The heating rate was 10°C min-’ and the sample size ranged between 3-10 mg. The drug has one endothermic peak, showing no signs of decomposition at its melting point. The following table illustrates the difference in heat of fusion and peak temperature of the known polymorphic forms. Polymorph I Polymorph I1 Polymorph Ill

AH.J/G 102.0 100.5 82.4

Peak Temp.”C 151.1 147.8 143.5

I

I

\

tI

IU

\

Figure ( 1 a): DSC Curves of Terfenadine Polymorphic Forms I, 11 and III.

Figure ( 1 b): DSC Curve of Terfenadine Glass Form.

TER FENADINE 635


636

4.3. Solubility

The solubility of the most stable polymorphof terfenadinewas determined by shaking the excess of the drug in various solvents till equillibrium at 30°C. Equillibriumsolubility is presented in table (I).

TABLE(1)

Terfenadine EquillibriumSolubility in Different Solvents at 30°C Solvent

Solubility Gm/100ml

30°C

Water Ethanol Methanol Hexane 0.1 M Hydrochloric Acid 0.1M Citric Acid 0.1 M Tartaric Acid

0.001 3.780 3.750 0.034 0.012 0.110 0.045

Terfenadine is highly hydrophobic, tends to adsorb on surfaces. It’s solubility is slightly improved in mineral acids but increases appreciably in relatively high concentrationsof hydroxy acids (5). It was shown that solubility improved by the addition of even low concentrations of sodium chloride to hydrochloric acid-terfenadine solutions and monobasic sodium phosphate to phosphoric acid-terfenadine solution (6). The drug solution in ethanol and methanol is sticky and deposits terfenadine glass form when the solvent evaporates (5). Terfenadine citrate and tartarate has a distinct surface activity and their solubility is pronouncely higher than terfenadine. Different polymorphic and glass forms showed gradual transformationto the stable form in the presence of water. The dissolution rate was highest for the glass form followed by polymorph Ill and polymorph II, respectively. In addition, solubility increased appreciably by complexingwith cyclodextrinsand polyethyleneglycols.

TERFENADINE

637

4.4. DissociationConstant

The pKa of terfenadine is 10. This is an approximate value as reported earlier(7). However, pKa of terfenadine hydrochloride was determined by titration against 0.01 M potassium hydroxide, both dissolved in different concentrations of methanol-water mixtures. The apparent pKa was obtained by extrapolation technique(8) and was 6.56 at 22"C(9).

4.5. Spectral Properties 4.5.1. Ultraviolet spectrum:

Terfenadine solution in methanol was screened between 220-350nm using Beckman DU7 spectrophotometer. It exhibited two maxima at 260nm and 225nm with a shoulder at 254nm, figure (2). The molar absorptivities for terfenadine in some selected commonly used solvents are shown in table (11).

TABLE(I1)

Molar Absorptivities of Terfenadine in Some Commonly Used Solvents Solvent

Methanol Ethanol Dichloromethane

Max.Wavelength nm

Molar Absorptivities

260 260 260

660.4 671.7 762.2

638


WAVELENGTH nm

Figure (2): The UVAbsorptionSpectrum of Terfenadine in Methanol.

TERFENADINE

639

4.5.2. Flourescence spectrum Terfenadine solution in buffer pH2 (citric acid-sodium dihydrogen phosphate) showed excitation and emission maxima at 260 and 289nm respectively. The spectrum was recorded on Kontron SFM25 spectrofluorometer,figure (3). 120%

100%

c

m z W I-

W

80%

L

3 W

a

60%

i

40%

20%

0%

200

I I

I

I

I

220

240

260

280

\ I I

I

300

320

WAVELENGTH nm

Figure (3): The Fluorescence Excitation and Emission Spectrum of Terfenadine in Buffer solution pH 2.0.

2


640

4.5.3. Infrared spectrum

Terfenadine infrared spectra presentingpolymorph 1,111 and theglass form prepared as a dispersion in KBr were obtained using Shimadzu IR-435 spectrophotometer, figure (4a,b and c). Spectral assignments for principal absorption bands of polymorph I are given in table (111) showing consistency with the proposed structure. I.R. spectra of polymorphic forms Iand Ill showed little differences. Neverthelesssome differences were observed in the regions 1400-1300 cm-', 1300-1150 cm-', these regions are responsible for C-H bending and C - 0 streching in these polymorphic forms. However, glass terfenadine showed a distinct difference in the region 3500-3200 cm-' where polymorph Ill displayed a band at 3500 cm-' and a shoulder at 3400 cm-'. Glass form showed broad bands at 3400 cm-l and 3300 cm-'. Such broadness may be due to intermolecular hydrogen bonding of OH group. Generally, the differences in terfenadine polymorphic forms are very negligible indicating the lack of intramolecularinteraction.

TABLE (111)

Band Assignments of Infrared Spectrum of Terfenadine Band Frequency cm'' 3250,3240 3000 2900 1370,1390 1150,1100 830 750,630

FunctionalGroup

0-H stretching vibration for two hydroxyl groups. C-H stretchingvibration for aromatic hydrogens. C H stretching vibration for the aliphatic hydrogens. C-H streching for tert-butylgroup, doublet. C-0 streching vibration for C-OH groups of 3" and 2" alcohols, respectively. C-H out of plane bending for aromatic C-H of para disubstituted benzene. C-H out of plane bending for aromatic C-H of mono substitutedbenzene.

'"1 90

Figure (4a): 1.R. Spectrum of Polymotph 1. - KBr Disc.

E 01 4oM)

3OOo

I

I

2Ooo

l6W

WAVENUMBER

1600

1400

1200

CM-’

Figure (4b): 1. R. Spectrum of Polymorph 111 - KBr Disc.

loo0

Boo

T MKI

4Mk)

3Ooo

2ooo

1800

WAVENUMBER

1600

1400

CM-’

Figure (4): 1.R. Spectrum of Glass - KBr Disc.

.

1206

I

loo0

m

1

600

644

4.5.4.


Mass spectra

4.5.4.1. Electron impact (El): The electron impact mass spectrum of terfenadine is shown in figure (5). The spectrum was obtained by direct solid insertionprobe at electron energy of 70 eV using HitachiPerkin Elmer RMU-GH mass spectrometer. The spectrum shows a molecular ion peak M+ at a mass/ charge (m/z) ratio of 471 and a base peak at 280 corresponding to the =-cleavage at the nitrogen atom. Other fragments including diphenylhydroxymethyl ion and tert-butyl radical were displayed as well (at m/z = 183,57). The pertinentfragments, their relativeintensitiesand proposed structure are presented in table (IV).The mass spectra of the dehydration product of terfenadine was previously reported showing ion peak at m/z 453 (M+, 280 and 183) (10).

TABLE (IV) Mass Spectral (Electron Impact) Assignment for Terfenadine

M/z

Relative Intensity%

47 1

55.6

453

4.3

280

100

183

13

105

13

57

18

Fragment Ion

MI + M - 181'

r. v)

8

t5

. -v) 0

m

I 0


646

4.5.4.2. Chemical ionization (CI): The spectrum was recorded on Varian MAT-44 spectrometer, figure (6). The spectrum shows a prominant pseudo molecular ion at m/z ratio of 472 and an ion peak at 454 corresponding to the dehydratedfragment. 4.5.5. Nuclear magnetic resonance 4.5.5.1. Proton magnetic resonance: The NMR spectrum was obtained on a Bruker WP 80 SY instrument of a solution of terfenadine in deuterated chloroform. The spectrum is presented in figure (7). The assignment of the protons and their multiplicity pattern is listed in table (V). Difficulty was encountered in assigning the protons of the hydroxyl groups. One of the protons was masked by the multiplet corresponding to the aliphatic protons absorbing at 2.0-2.4 ppm. This assumption was supported by a deuterium exchange experiment. However, the exchange did not reveal the possible absorption assignment for the second hydroxyl proton. Using dimethylsulfoxideas a solvent alone or with D20,was not indicativedue to the change in the absorption spectrum which could be explained by the hydrogen bonding properties of the solvent. Therefore, it could be assumed that the second hydroxylproton absorbs in the same range as the multiplets of aliphatic protons extending from 1.9-2.4 ppm.

TABLE (V) Proton NMR Assignments of Terfenadine ~~

Chemclal Shift H PPm

-

7.4 7.5

-

7.19 7.26 4.5 4.59 2.8-3.1 2.0 2.4 1.5-1.9

-

Relative Number of protons (pattern)

Assignment

14cd0ub'eb Disubstituted aromatic rings protons.

Singlet 1 (t, broad) 2 (m, broad) 5 (m, broad) 10 (m, broad)

Monosubstituted aromatic rings protons Ci H

C4H2 Cp)H2, CB)H2, 0 - H C2H2,C3H2,piperidine ring protons at C$ , Cq) , Cgl , 0-H Tert-butyl protons

472

183

20

266

( I

313 100

150

200

250

300

338

..

m

350

376 a

528

I

.

400

450 M/Z

Figure (6): The Chemical Ionization Spectrum of Terfenadine.

500

550

I

10 0

I 75

I 50

I 2.5

'

PROTON SHIFT

Figure (7): Proton NMR Spectrum of Terfenadine.

!

I 00

mENADINE

649

4.5.5.2. Carbon - 13: Carbon-13 NMR spectra were recorded on Varian FT-80A spectrometer. The assignment, listed in table (VI) was further confirmed by carrying out an inverse polarization transfer study. The recorded spectra are shown in figure (88).

I 75

I 50

I

I

25

00

PROTON SHIFT

Figure (8): '%arbon NMR Spectrum of Terfenadine in DMSO.


650

TABLE (VI)

Carbon - 13 NMR Assignments of Terfenadine Chemical Shift

C ppm

24.17 25.93 31.60 34.50 39.75 44.26 53.45 54.80 58.90 73.41 79.33 125.01 125.59 125.96 126.35 128.16 142.81 146.49, 146.62 149.39

Assignment c3

Cd Cgl tert-butylC (CH3) tert-butyl C. @Ha) I

c;Cd Cd

c4 c4 C1 CCC C$, Cg)r

,c; cg

ortho carbons-benzhydryl para carbons-benzhydryl meta carbons-benzhydryl Cql Epsi carbons-benzhydryl C1”

4.5.6. X-Ray powder diffraction

The x-ray powder diffractionsof I and 111 polymorphic forms of terfenadine were determined by Philips PW 1050-81 Goniometer with a PW 1729 Generator, It was equipped with nickle filtered copper radiation with = 1.541 nm. The interplanner distance and relative intensity of the major peaks for the stable and metastable forms of terfenadine are listed in tables (VII and VIII). Figure (9a,b) presents x-ray powder diffraction pattern for polymorph I and Ill.

I

50

I

I

4 5 4 0

I

35

I

30

I

25

I

20

I

15

I 10

I

5

Figure (9a): Powder X-Ray Diffraction Pattern of TerfenadinePolymorph 1.

I

~

1

4

1

I

5

4

0

I

3

5

I

I

~

2

5

2

0

A4 I

I

1

5

1

I

0

5

Figure (9b): Powder X-Ray Diffraction Pattern of Terfenadine Polymorph 111.

653

TERFENADINE

TABLE (W)

X-Ray Powder Diffraction of Terfenadine Polyrnorph I Peak Angle (28)

06.4 07.3 12.5 12.1 15.6 16.6 17.5 18.5 19.8 22.3 24.3 25.0 26.3 27.9 28.5 30.5

Interplanner Dlstance d' ('A)

**i/lmax (%)

13.81 12.11 07.08 06.28 05.68 05.34 05.06 04.79 04.48 03.98 03.66 03.56 03.38 03.19 03.13 02.93

100 04.32 35.8 51.2 13.82 43.2

09.87 09.87 55.5 20.9 05.55 22.2 10.49 02.83 06.17 03.7

d =n/2SinO tt

Rased on the highest intensity of 1.000

TABLE(VII1)

X-Ray Powder Diffractionof Terfenadine Polyrnorph Ill ~

~~

Peak Angle (28)

Interplanner Dlstance d' (Ao)

**flmax (%)

12.62 07.83 06.51 05.79 05.15 04.93 04.37 04.15 03.92 03.78 03.25 03.18 02.99

46.38 10.24 93.37 06.62 05.42 100 12.04 18.67 14.45 04.21 03.61 03.61 03.01

07.0 11.3 13.6 15.3 17.2 18.0 20.3 21.4 22.7 23.5 27.4 28.0 29.8

**

d=n/2Sine. Based on the highest intensity of 1.WO

654


5. METHODS OF ANALYSIS

5.1. Stattlng Materialand PharmaceuticalDosage Forms 5.1.1. Elementalanalysis Calculatedfor C32H4,N02 C 81.45 H 8.76 N 2.97

Found 81.48 8.77 2.96

5.1.2. Non-aqueous titration Terfenadinewas dissolved in glacial acetic acid and titrated against 0.1 M perchloric acid. Each ml of 0.1 M perchloric acid is equivalent to 47.169 mg of the drug. As anticipated this method suffers from excipients interferences hamperingits use in dosage forms (3 and 11).

5.1.3. Spectrophotometrlcmethods 5.1.3.1. Ultraviolet absorption: Terfenadine was dissolved in a mixtureof methanol, acetic acid and water in the following proportions (50:6:44), respectively. The absorbance was read at two maxima 260nm and 238 nm. This method could be applied to concentrations ranging, 0.1 -0.6 mg.mL-’. However, the extensioncoefficient is low and the interferencefrom additives is clearly observed(l1). 5.1.3.2. First derivative: A method for terfenadine determination, by first derivative peak height amplitude measurements, at two different wavelengths is possible, (Figure 10). The accuracy and precision of the method is demonstrated with 99.3% recovery and less than 1% standard deviation for solutions concentration ranging 0.1 -1.O mg. mL-’ in methanol at 271.5 nm. Beer’s Lamberts law was obeyed for dissolutiontesting of lower concentrations ranging 0.005 mg to 0.006 mg. mL-l at 224.2nm in 0.1 M HCI. The described method have shown to eliminate the background distortion due to excipients. This method could be appliedto tablets, suspensionand capsules(12).

+0.120

X

5

O.OO0

-0.120

Figure (1 0): The First Derivative Spectrum of Terfenadine in Methanol.


656

5.1 -3.3. Colourimetricspectroscopy: a

- Terfenadine formed an ion pair complex with methyl orange which was extracted in dichloromethane and showed maxima at 427 nm. The colour obtainedwas stable and the complexobeyed Beer’s Lambert law between 0.004-0.01 6 mg.mL’. The optimum pH of the aqueous layer was ranging from 3.5-6.0. This method was applied for tablets, capsules, suspension and content uniformity testing(l1).

b

-A

c

-

bluish green colour resulted from the reaction between terfenadine and 7,7, 8,8-tetracyanoquinodimethane. The absorption was measured at 845 nm. Beer’s law is obeyed over the terfenadine concentration range 0.002-0.01 2 mg. mL1.This method is applicable to tablets(l3).

Terfenadine iodine charge transfere complex was formed and the absorption was measured at 290nm. This method could be applied to tablets having concentrations2-12j~g.mL-‘(13).

5.1.4. Chromatographlc methods 5.1.4.1. Thin layer chromatography: Thin layer chromatography system (TLC) was developed to assay terfenadine in the bulk material. The mobile phase consisted of methanol, butanol, water, toluene and acetic acid mixed in proportions of 2.0:3.0: 1.0:2.0: 0.1, respectively. The solution of terfenadine in methanol(2-10mg.mL-l) was spotted with 5flL micropipetteon precoatedsilica gel plates (10 x 10 cm). The developed plates were read at 254 nm, a linear response for concentrations ranging from 2-1Omg.mL-’ was obtained(l1). 5.1.4.2. High pressure liquid chromatography: a

-

Synthesis Impurities: The method for synthetic impurities is an official test described in the current USP (3).

b

-

Bulk and Dosage Forms: Various HPLC systems were reported for terfenadine analysis in bulk and dosage forms. A brief description for these applied systems is given:

1

-

Reverse phase column (C18)with a mobile phase consisting of a mixture of 0.1 triethylammonium acetate buffer having pH5, acetonitrile and methanol at ratios of 6.25: 6.25: 87.5

TERFENADINE

65 7

respectively. The injection loop used was 10 pL. The internal standard was ephedrine hydrochloride with retention time 3.4 min., flow rate was 2 mL.min-’. The terfenadine retention time was 4.2 min. and detection was carried out at 254 nm and could be obtained in a limit of 0.1-0.8 mg.mL-l(l4). 2

-

Ion pair HPLC assay using ODS column (5 um) with a mobile phase consisting of 0.01 M n-hexane sulphonate in acetonitrile (80 parts) water (20 parts) containing 0.1 % glacial acetic acid. The maximum limit of injection was 170uL and the flow rate was 1mL.min-’withquinineas interna1standard.The retention times of quinine and terfenadinewere at 4.7and 6.7 min,respectively.The detection was carried out at 218 nm (0.64 AUFS). Terfenadine-quininepeak area ratio was linear over 68-544 ng of terfenadine injected(l5).

3

-

Reverse phase column spherisorb ODs-2 (3-urn)was used with a mobile phase of 60/40 v/v acetonitrilelwater made with 0.012M in sodium phosphate buffer (ca pH 2.3) and 0.021M in sodium perchlorate. Injection volume of 20 p L was used. The flow rate was 1.5 mL.min-’. The detection was carried out at 210 nm at 0.23 AUFS. Retention time for terfenadine was 4.5 min. This stability indicating method was used to assay the drug (0.3-3.0mg.mL-’) in the presence of ibuprofen and pseudoephedrinehydrochloridein aqueous solutions containing tween 80 and methyl cellulose(l6).

4

-

Reverse phase column (C18)Bonda Pack with a mobile phase consisting of 0.25M sodium acetate buffer (pH5) added to acetonitrile (1:1 v/v). The injection loop was 2 0 ~ and L the flow rate was 1 mL.rnin-’. the detectionwas carried out at 225 nm. The internal standard was thiothxane having retentiontime 9.8 min., while the retentiontime of terfenadinewas 14.5 min. This method achieved measurement between 10-80ug.rnL-’(l7).

5

- Zorbax

C-8 column, (6 urn), (15 cm x 4.6 mm as internal diameter) was used. Mobile phase consisted of acetonitrile-0.1M triethylammonium phosphate buffer (pH7) mixed in 70:30 v/v ratios. The loop used was 100lL. The flow rate was 1SmL.rnin-’ and the measurement was monitored at 260 nm and by flouresence detector (EX260 nm and EM289 nm). The retention time was 4.8 min. This method could differentiate various degraded products from the parent compound. The method showed linear UV (260nm) response between 6 and 60,ug injected (10).

658


5.2. Body Tissues and Fluids. 5.2.1. Radioimmunoassay: The method consisted of extracting terfenadine from alkalinized plasma into hexane. Aliquots of the hexane extract were evaporated to dryness. To this residue was added tritium-labelledterfenadine in aqueous ethanol, phosphate buffered saline and terfenadine antisera. The mixture was then incubated overnight at 4°C and unbound terfenadine subsequently removed with charcoal. After centrifugation, the supernatant was decanted into scintillation vials, mixed with scintillator (0.6% Omniflour, New England Nuclear, in a 2:l mixture of Toluene/ Triton X-100) and counted in a Beckman LS-300 Liquid Scintillation Spectrometer. The counts per minute (cpm) of the unknown plasma samples were compared to a standard curve that was processedalong with the sample. The recovery of terfenadinethrough the extraction procedure was shown to be 90%(18).

5.2.2. 14Canalysis Analysis of 14Cconcentrations in all biological samples from the material balance study was by combustion (faeces were homogenized with 9 volumes of water) of dried residues in a Packard Model 3068 sample Oxidizer followed by liquid scintillation counting in a Packard Tri Carb Scintillation Counter (Model 3320). Quench correction was by automatic external standard channel ratio method(l8).

5.2.3. Gas chromatography-Mass spectrometry A Dupont 321 GC/MS was used to analyse terfenadine metabolites. Two types of urine extracts were subjected to GC/MS analysis for structure elucidation, namely a pH12 toluene extract (metabolite II) (la), and pH4 ethyl acetate extract (metabolite I). The GC/MS conditions were as follows for: Metabolite II: 6 ft glass column, packed with 5% OV-17, (Chrom WHP, 100/120 mesh); injector, column and separator temperature: 250°C; ionization voltage: 70 eV; mass range: 60-400 (amu); integration time: 10 mqamu. Metabolite I: 2 ft glass column packed with 1% Dexsil (Chrom WHP, 100/120 mesh); injector temperature: 250°C; column temperature: 280°C; separator temperature:250°C; ionizationvoltage: 70 eV; mass range: 250-750 (amu); integrationtime: 10 ms/amu.

TERFENADINE

659

6. STABILITY

6.1. Stability of the Solid Terfenadine powder is stable against heat and light. No degradation products where observed after 12 months storage in amber colour glass at 40°C and under room light conditions. The solid dosage form is still stable for 4 years during storage at room temperature (10,19).

6.2. Stability in Solutlon Terfenadine dispersion has excellent stability at p, i 5-11 when protected from intense light. A low level of degradation is observed at pH 1.5 in darkness after 25 weeks storage. The stability of terfenadine is not effected by oxygen if the solution is protected from light. Even under intense flourescent light, terfenadine remains stable for up to 8 weeks storage at 27"C(10).

7. PHARMACOKINETICS

Australian National Drug Information Service compiled a short but thorough profile on terfenadine pharmacology and therapeutics. The following part concerning pharmacokineticswas extracted as producedfrom that profile which has a useful reference list(7).

7.1. Absorption Terfenadine is completely and rapidly absorbed from the gastrointestinal tract and undergoes extensive biotransformation (over 99%) probably by first-pass metabolism in the liver. Mean peak plasma concentration after administration of a 60 mg tablet was 0.84 k 0.43 (range 0.26-1.92) nanograms.mL-' , (measuredby radioimmunoassay (RIA)) which was reached in 1.74 k 1.47 (range 0.5-12) hours. A linear correlation was noted between dosage and peak plasma concentration after single doses of 60 and 180 mg terfenadine suspension. Mean peak plasma concentrations for these doses were 1.544 f 0.726 and 4.51 9 k 2.002 nanograms.mL-', respectively, and


660

were achieved in approximately 1 hour. However, Area Under the Curve (AUC) calculations indicated non linear kinetics with an almost four-fold increase in peak plasma concentrationfor the three-fold increase in dose.

7.2. Bioavaiiabiiity

Tablet and suspension formulations were found to be bioequivalent. The AUC for 0-48 hours values were not significantlydifferent. For exampleAUC for 60 mg suspension was 11.4 hour nanograms.mL-' and for 60 mg tablet 10.3 hours nanograms.mL-'. The 180 mg tablet AUC was 39.2 hours nanograms.mL " while the 180 mg suspension AUC was 43.2 hours nanograms.mL-'. Peak plasma levels (PPL), were higher for the suspension than for the correspondingtablet doses, for 60 mg dose the PPL for tablets and suspension were 0.84 and 1.44 nanograms.mL', respectively. When 180 mg doses were given the PPL for tablets and suspension were 2.58 and 4.46 nanograms.mL-', respectively. These data indicate that the drug is more rapidly absorbed from the suspension but the total quantity of drug absorbed from the two formulations is similar.

7.3. Distribution

Animal studies indicate that labelled terfenadine is distributed widely with highest concentrations occurring in liver and gastrointestinal tract supporting the assertion that biliary mechanisms play a major role in the metabolic disposition of terfenadine. Levels of terfenadine in rat brain were low after IV dosing of 10md kg and not detectable after a similar oral dose. There is no information available on the distribution of terfenadine in humans.

7.4. Protein Binding

Terfenadine is 96 to 97% bound to human serum albumin.

TERFENADINE

66 1

7.5. Metabolism Comparisons of plasma concentration data derived from RIA and C-14 labelled studies indicate that the degree of terfenadine biotransformation in humans is over 99% and that first pass metabolismmay play a major role in the disposition of terfenadine. Three metabolites have been identified in man: the carboxylic acid analogue of terfenadine (metabolite I), and its corresponding ester and the piperidine carbinol derivative (metabolite 11). The latter metabolite is a synthetic precursor of terfenadine and has no significant antihistamine activity. The other metabolites do display antihistamine activity in the isolated guinea pig ileum. Although relative antihistaminepotency was not investigated thoroughly, the carboxylic acid derivative (metabolite I) is probably about 30% as potent as terfenadine. Terfenadine undergoes oxidation of one of the methyl groups of the t-butyl substituent to produce metabolite I which is probably formed from the oxidation of an intermediate alcohol. This metabolite is found in both urine and faeces. Metabolite II is found primarily in urine and presumably arises from oxidative dealkylation of the substituted butanol side chain attached to the piperidine nitrogen atom.

7.6. Excretion

Terfenadine is excreted mainly in the faeces and to a lesser extent in the urine as metabolites. Approximately 40% of a radioactive labelled dose of terfenadine appeared in the urine in 5 days whilst 60% was recovered in the faeces in 12 days. Metabolites I and II accounted for 38 and 33% of the urinary radioactivity respectively, whereas (metabolite I) accounted for 49% of the faecal radioactivity.

7.7. Half-Life

The distribution half-life of terfenadine is 3.4 hours and the elimination half-life is 20.3hours.

ADNAN A. BADWAN ET AL.

662

REFERENCES (1) A.A. Carr and D.R. Meyer; Arzneim-Forsch/ Drug Research 32 (11) 9a 1157 (1982). (2) A.A. Badwan, T.A. Arafat, M.Saleh, A. Abu-Malooh, M. Sheikh Salemand Hanan N. Al-Kaysi. Preparation, Characterizationand Transformationof Terfenadine Polymorphic Forms, to be Published. (3) Terfenadine Monograph, USP XXll Supp. 1 page 2173 (1990). (4) M. Sheikh Salem, M.A. Hassan, H.N. Al-Kaysi, T.A. Arafat, A. Abu-Malooh and A.A. Badwan. 5th International Conference of PharmaceuticalTechnology, Paris Vol. 2 page 359 (1989). (5) A.A. Badwan; Unpublished Data. The Jordanian Pharmaceutical ManufacturingCo. (6) W.H. Streng, S.K. Hsi, P.E. Helms, H.G.H. Tan, J. Pharm.Sci. 73 (12) 1679 (1984). (7) Australian National Drug Information Service. The Australian Journal of Pharmacy 67 Dec. 1077 (1986). (8) D.W. Newton, W.J. Murray, and M.W. Lovell, J. Pharm. Sci. 71 (12) 1363 (1982). (9) M. Omari; Unpublished Data. The Jordanian Pharmaceutical ManufacturingCo. (10) T. Man Chen, A.D. Silland and C.L. Housnyer; J. Pharm. Biomed. Analysis 4 (4) 533 (1986) (11) A.A. Badwan, A. Abu-Malooh, L. Owais, M. Sheikh Salem and H.N. Al-Kaysi;

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