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Loftsson T. 1,4-Benzodiazepines: Chemical stability and cyclodextrin solubilization. J Drug Deliv Sci Technol 2021. [DOI: 10.1016/j.jddst.2021.102936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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2
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Kwak JS, Zhang WP, Mallik D, Organ MG. Intelligent Multidimensional Purity Analysis and Confirmation Tool for Multiple Attribute Analysis. Anal Chem 2021; 93:3905-3913. [PMID: 33605714 DOI: 10.1021/acs.analchem.0c04652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Chiral active pharmaceutical ingredients (APIs) are known to bind to chiral biological targets with better on-target specificity than achiral ones. However, the methods of synthesizing such APIs stereoselectively require the exhaustive optimization of multiple quality attributes of an asymmetric synthesis, wherein all critical quality attributes (for example, chemical and stereochemical purity of the API) are to be optimized in parallel and ideally from the beginning of the drug development program. A multidimensional liquid chromatographic tool capable of simultaneously measuring multiple quality attributes from a single analytical injection is reported. The tool is designed for the recirculation of chromatographic eluent bearing an analyte of interest through one or more stationary phases using a new and uniquely designed heart-cut valve. The iterative measurement of a target analyte from just one single injection will help scientists identify whether an unknown impurity is formed during reaction or during analysis. This chromatographic tool is particularly useful in the discovery of on-analysis artifacts, which is a resource-intensive exercise involving the identification, synthesis, and injection of impurity standards, all of which delay the drug development program.
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Affiliation(s)
- Jee Seong Kwak
- Flow Chemistry Facility, Centre for Catalysis Research and Innovation (CCRI) and Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5, Canada.,Department of Chemistry, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada
| | - Wenyao Peter Zhang
- Department of Chemistry, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada
| | - Debasis Mallik
- Flow Chemistry Facility, Centre for Catalysis Research and Innovation (CCRI) and Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5, Canada.,Department of Chemistry, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada
| | - Michael G Organ
- Flow Chemistry Facility, Centre for Catalysis Research and Innovation (CCRI) and Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5, Canada.,Department of Chemistry, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada
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3
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Ballard A, Narduolo S, Ahmed HO, Keymer NI, Asaad N, Cosgrove DA, Buurma NJ, Leach AG. Racemisation in Chemistry and Biology. Chemistry 2020; 26:3661-3687. [PMID: 31709642 DOI: 10.1002/chem.201903917] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Indexed: 11/09/2022]
Abstract
The two enantiomers of a compound often have profoundly different biological properties and thus their liability to racemisation in aqueous solutions is an important piece of information. The authors reviewed the available data concerning the process of racemisation in vivo, in the presence of biological molecules (e.g., racemase enzymes, serum albumin, cofactors and derivatives) and under purely chemical but aqueous conditions (acid, base and other aqueous systems). Mechanistic studies are described critically in light of reported kinetic data. The types of experimental measurement that can be used to effectively determine rate constants of racemisation in various conditions are discussed and the data they provide is summarised. The proposed origins of enzymatic racemisation are presented and suggest ways to promote the process that are different from processes taking place in bulk water. Experimental and computational studies that provide understanding and quantitative predictions of racemisation risk are also presented.
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Affiliation(s)
- Andrew Ballard
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Stefania Narduolo
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Hiwa O Ahmed
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK.,Pharmaceutical Chemistry Department, Hawler Medical University, Erbil, Kurdistan Region, Iraq
| | - Nathaniel I Keymer
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Nabil Asaad
- AstraZeneca, Mereside, Alderley Park, Macclesfield, SK10 4TG, UK
| | | | - Niklaas J Buurma
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Andrew G Leach
- Division of Pharmacy and Optometry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
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4
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Hok L, BoŽičević L, Sremec H, Šakić D, Vrček V. Racemization of oxazepam and chiral 1,4-benzodiazepines. DFT study of the reaction mechanism in aqueous solution. Org Biomol Chem 2019; 17:1471-1479. [PMID: 30676597 DOI: 10.1039/c8ob02991a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The tranquilizer and hypnotic drug oxazepam undergoes the racemization process in aqueous medium, which is relevant for its pharmacological profile. The experimental barrier value (ΔG‡298 ≈ 91 kJ mol-1) was determined earlier, but the exact mechanism of enantiomerization is not known. Four different mechanisms have been proposed in the literature: C3-H/H exchange reaction, keto-enol tautomerization, solvolytic identity reaction, and ring-chain tautomerization. However, none of the reported reactions has been confirmed as the main pathway for racemization. In this work, all these mechanisms were subjected to comprehensive analysis performed by high-level quantum-chemical models. Two density functionals (B3LYP and M062X) were employed for geometry optimization of all stationary points at the corresponding potential surfaces, and the double-hybrid model (B2PLYP) was used for improved energy calculations. Out of all the tested mechanisms, only the ring-chain tautomerism fits the two experimental targets: the measured energy barrier and the pH-rate profile of racemization. The latter reveals that no acid/base catalysis is required for racemization to occur. The ring-chain tautomerism is initiated by intramolecular proton transfer from the C3-hydroxyl group to the imine nitrogen, which triggers the benzodiazepine ring opening and the formation of the achiral aldehyde intermediate. The latter undergoes ring closure which results in the inverted configuration at the C3-chiral atom of oxazepam. Our computational results suggest that the same mechanism is operative in the fast racemization of different 1,4-benzodiazepines, which posses the hydroxyl group at the stereogenic C3-centre (e.g. lorazepam or temazepam). In other benzodiazepine members (e.g. cinazepam or camazepam) the keto-enol tautomerization and/or the C3-H/H exchange mechanism may become relevant for their much slower racemization. This computational study is not only revealing in terms of mechanistic details, but also has predictive power for optical stability estimates in the family of benzodiazepines and similar heterocycles.
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Affiliation(s)
- Lucija Hok
- Faculty of Pharmacy and Biochemistry, University of Zagreb, Ante Kovačića 1, 10000 Zagreb, Croatia.
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5
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Testa B, Vistoli G, Pedretti A. Mechanisms and pharmaceutical consequences of processes of stereoisomerisation — A didactic excursion. Eur J Pharm Sci 2016; 88:101-23. [DOI: 10.1016/j.ejps.2016.04.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 04/02/2016] [Accepted: 04/05/2016] [Indexed: 11/29/2022]
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6
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Abstract
Stereochemical factors are known to play a significant role in the metabolism of drugs and other xenobiotics. Following Prelog's lead, types of metabolic stereoselectivity can be categorized as (i) substrate stereoselectivity (the differential metabolism of two or more stereoisomeric substrates) and (ii) product stereoselectivity (the differential formation of two or more stereoisomeric metabolites from a single substrate). Combinations of the two categories exist as (iii) substrate-product stereoselectivities, meaning that product stereoselectivity itself is substrate stereoselective. Here, published examples of metabolic stereoselectivities are examined in the light of these concepts. In parallel, a graphical scheme is presented with a view to facilitate learning and help researchers to solve classification problems.
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Affiliation(s)
- Bernard Testa
- Department of Pharmacy, Lausanne University Hospital , Lausanne , Switzerland
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7
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8
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Lange J, Haberland D, Thede R. Separate Determination of Rate Constants from Reversible Reactions in a Chromatographic Column and Eluent Using Empirical Peak Shape Equations. J LIQ CHROMATOGR R T 2007. [DOI: 10.1081/jlc-120017169] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Jana Lange
- a Institute of Chemistry and Biochemistry , University of Greifswald , Soldmannstrasse 23, D-17489 , Greifswald , Germany
| | - Detlef Haberland
- a Institute of Chemistry and Biochemistry , University of Greifswald , Soldmannstrasse 23, D-17489 , Greifswald , Germany
| | - Richard Thede
- a Institute of Chemistry and Biochemistry , University of Greifswald , Soldmannstrasse 23, D-17489 , Greifswald , Germany
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9
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Ali I, Gupta VK, Aboul-Enein HY, Singh P, Sharma B. Role of racemization in optically active drugs development. Chirality 2007; 19:453-63. [PMID: 17393472 DOI: 10.1002/chir.20397] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
U.S. Food and Drug Administration issues certain guidelines for marketing of optically active drugs as some enantiomers racemize into human body, leading to the generation of other antipodes, which may be toxic or ballast to the human beings. Moreover, racemization reduces the administrated dosage concentration as optically active enantiomer converted into its inactive counter part. Therefore, the study of racemization of such type of drugs is an important and urgent need of today. This article describes in vitro and in vivo racemization of optically active drugs. The racemization process of various optically active drugs has been discussed considering the effect of different variables i.e. pH, temperature, concentration of the drug, ionic concentration, etc. Attempts have also been made to discuss the mechanisms of racemization. Besides, efforts have been made to suggest the safe dosages of such type of drugs too.
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Affiliation(s)
- Imran Ali
- Department of Chemistry, Faculty of Natural Sciences, Jamia Millia Islamia University, Jamia Nagar, New Delhi, India
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10
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Pham-Huy C, Villain-Pautet G, Hua H, Chikhi-Chorfi N, Galons H, Thevenin M, Claude JR, Warnet JM. Separation of oxazepam, lorazepam, and temazepam enantiomers by HPLC on a derivatized cyclodextrin-bonded phase: application to the determination of oxazepam in plasma. JOURNAL OF BIOCHEMICAL AND BIOPHYSICAL METHODS 2002; 54:287-99. [PMID: 12543505 DOI: 10.1016/s0165-022x(02)00123-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The enantioselective high-performance liquid chromatography (HPLC) of three racemic 3-hydroxybenzodiazepines, oxazepam (Oxa), lorazepam (Lor), and temazepam (Tem), is a difficult operation because of the spontaneous chiral inversion in polar solvent. To solve this problem, we have developed an HPLC method based on a chiral Cyclobond I-2000 RSP column, maintained at 12 degrees C, and a reversed mobile phase (acetonitrile in 1% triethylamine acetate buffer, TEAA) at a flow rate of 0.4 ml/min. Peaks were detected by a photodiode-array detector at 230 nm for quantification and by an optical rotation detector for identification of (+) and (-) enantiomers. The results showed that peak resolutions of Oxa, Lor, and Tem enantiomers, analyzed under the same conditions, were 3.2, 2.0, and 1.8, respectively. For the determination of Oxa enantiomers in plasma of rabbits, extraction with diethyl ether at pH 1.5, a polar organic mobile phase, and a Cyclobond I-2000 SP column were used. Other analytical conditions were the same as previously described. Blood samples were immediately cooled at 4 degrees C and centrifuged at 0 degrees C for the collection of plasma. The results showed a difference in plasma S(+)- and R(-)-oxazepam concentrations in rabbits. No racemization of S(+)- or R(-)-Oxa enantiomers, added alone to blank plasma, was observed after extraction and enantioselective HPLC analysis.
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Affiliation(s)
- Chuong Pham-Huy
- Laboratory of Toxicology, Faculty of Pharmacy, University of Paris V, 4 avenue de l'Observatoire, 75006 Paris, France.
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11
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Trapp O, Trapp G, Schurig V. Direct calculation and computer simulation of the enantiomerization barrier of oxazepam in dynamic HPLC experiments--a comparative study. JOURNAL OF BIOCHEMICAL AND BIOPHYSICAL METHODS 2002; 54:301-13. [PMID: 12543506 DOI: 10.1016/s0165-022x(02)00118-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Dynamic chromatographic methods constitute a versatile approach to the rapid and precise determination of enantiomerization barriers of stereolabile drugs. In the present study enantioselective dynamic high-performance liquid chromatography (DHPLC) was employed to determine the enantiomerization barrier of oxazepam. Dynamic elution profiles, exhibiting plateau formation and/or peak broadening between 20 and 60 degrees C at pH 2.6 and pH 8 were obtained in the presence of the chiral stationary phase (CSP) Nucleodex-beta-PM (permethylated beta-cyclodextrin chemically bonded to silica) using a 6:4 mixture of phosphate buffer and methanol as mobile phase. Evaluation of the experimental chromatograms was performed by the novel approximation function (AF) (without computer simulation), and by the stochastic model implemented in the ChromWin simulation software (with computer simulation) furnishing the respective apparent forward rate constants, k(1)(app)(T). From the rate constants, k(1)(app)(T), measured at variable temperatures, the kinetic Eyring activation parameters, deltaG(T)(#), deltaH(#) and deltaS(#), of the enantiomerization of oxazepam were obtained. By variation of the flow rate of the mobile phase, the expected independence of the enantiomerization barrier from the chromatographic time scale was demonstrated for the first time.
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Affiliation(s)
- Oliver Trapp
- Institute of Organic Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
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12
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13
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Smyth WF, McClean S. A critical evaluation of the application of capillary electrophoresis to the detection and determination of 1,4-benzodiazepine tranquilizers in formulations and body materials. Electrophoresis 1998; 19:2870-82. [PMID: 9870382 DOI: 10.1002/elps.1150191613] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Studies of the capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC) behaviour of 1,4-benzodiazepines have seen application in subject areas such as the development of pharmaceuticals, therapeutic drug monitoring and forensic toxicology. In the development of pharmaceuticals, pKa determinations by CZE can be used in preclinical studies whereas analytical data on the detection and determination of 1,4-benzodiazepines is of value primarily in raw material/formulation assay and in the analysis of body fluids in clinical studies. The capillary electrophoresis (CE) techniques, which generally have inferior limits of detection (LOD) to rival techniques such as gas chromatography (GC) and high-performance liquid chromatography (HPLC), are particularly applicable in forensic toxicology where reasonably high concentrations of these drugs can be encountered. It is anticipated that, with the interfacing of CZE and capillary electrochromatography (CEC) with mass spectrometry (MS) techniques, the excellent selectivity of CZE and particularly CEC will be effectively combined with the sensitivity of MS and the identification capabilities of tandem mass spectrometry (MS/MS) and MS hyphenated (MSn) techniques.
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Affiliation(s)
- W F Smyth
- ABCS School, University of Ulster, Coleraine, Northern Ireland.
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14
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Hofstetter H, Hofstetter O, Schurig V. Enantiomer separation using BSA as chiral stationary phase in affinity OTEC and OTLC. ACTA ACUST UNITED AC 1998. [DOI: 10.1002/(sici)1520-667x(1998)10:3<287::aid-mcs8>3.0.co;2-c] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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15
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Abstract
The use of immunoassay techniques represents an alternative approach to the more common chromatographic methods for the determination of the concentrations of chiral drugs. In the development of the former technique, the inherent stereoselectivity of the antibodies used appears to be an important parameter to be studied. The structural features of the drug, including the environment around the asymmetric center, the flexibility of the molecule and the ability of the molecule to undergo racemization, contribute to the molecule's ability to be recognized by stereoselective antibodies. These parameters are intrinsic and can not be influenced by the investigator. On the other hand, other parameters can be modified to favor the raising of highly stereoselective antibodies. These include the synthesis of an appropriate hapten; the selection of an optimal spacer arm between the hapten and the carrier protein used for the immunization procedure; and the choice of appropriate immunization and antibody-screening procedures. The purification of antibodies using affinity chromatography may also facilitate the selection of stereoselective antibodies.
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Affiliation(s)
- P A Got
- Departement de Bio-Analyse, Technologie Servier, Orléans, France
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16
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Nishikawa T, Hayashi Y, Suzuki S, Kubo H, Ohtani H. On-column enantiomerization of 3-hydroxybenzodiazepines during chiral liquid chromatography with optical rotation detection. J Chromatogr A 1997. [DOI: 10.1016/s0021-9673(96)01097-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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17
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Cabrera K, Jung M, Fluck M, Schurig V. Determination of enantiomerization barriers by computer simulation of experimental elution profiles obtained by high-performance liquid chromatography on a chiral stationary phase. J Chromatogr A 1996. [DOI: 10.1016/0021-9673(95)01230-3] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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18
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Boonkerd S, Detaevernier MR, Michotte Y, Vindevogel J. Suppression of chiral recognition of 3-hydroxy-1,4-benzodiazepines during micellar electrokinetic capillary chromatography with bile salts. J Chromatogr A 1995; 704:238-41. [PMID: 7599746 DOI: 10.1016/0021-9673(95)00098-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
During the development of a micellar electrokinetic chromatographic screening method for 1,4-benzodiazepines, peak splitting and broadening were observed for some 3-hydroxy-1,4-benzodiazepines (oxazepam, lorazepam, temazepam and lormetazepam). This phenomenon occurred when the micellar phase consisted of bile salts and can be ascribed to the chiral nature of these surfactants. As the bile salts were applied in order to reduce the capacity factors to an appropriate level, enantiomer separation was not an objective and even disturbing. By increasing the analysis temperature, the chiral recognition of these compounds could be suppressed.
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Affiliation(s)
- S Boonkerd
- Department of Pharmaceutical Chemistry and Drug Analysis, Vrije Universiteit Brussel, Belgium
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19
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20
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Abstract
Enantiomeric discrimination in drug disposition depends on the mechanism of the process under consideration. Absorption, distribution and excretion are generally passive processes which do not differentiate between enantiomers, but enzymic metabolism and protein binding, to plasma or tissue proteins, can show a high degree of stereoselectivity. In terms of metabolism, chiral discrimination occurs at both substrate and product levels, giving rise to five distinct stereochemical courses for drug metabolism, namely (i) prochiral-->chiral, (ii) chiral-->chiral, (iii) chiral-->diastereoisomer, (iv) chiral-->non-chiral and (v) chiral inversion. As a result, the metabolic and pharmacokinetic profiles of enantiomers after administration of racemic drugs can be very variable, so that the exposure to the two enantiomers may be very different. There now an enormous number of examples of each of these possibilities. The net result of the interaction of the stereoselectivities of these various processes can obscure the fact that one (or more) shows a marked stereoselectivity. This is particularly the case for metabolism: while the ratios of the total plasma clearance of the enantiomers of a wide range of drugs never exceed 2, individual metabolic pathways often show much greater stereoselectivity. This is particularly evident for those high-affinity, low-capacity enzyme systems which exhibit genetic polymorphism, namely the human cytochromes P450 2C18 and 2D6. This review provides an introduction to the stereoselectivity of drug metabolism.
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Affiliation(s)
- J Caldwell
- Department of Pharmacology and Toxicology, St. Mary's Hospital Medical School, Imperial College of Science, Technology and Medicine, London, UK
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21
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Yang SK. Substitution and racemization of 3-hydroxy- and 3-alkoxy-1,4-benzodiazepines in acidic aqueous solutions. Chirality 1995. [DOI: 10.1002/chir.530070510] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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22
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Cabrera K, Lubda D. Influence of temperature on chiral high-performance liquid chromatographic separations of oxazepam and Prominal on chemically bonded β-cyclodextrin as stationary phase. J Chromatogr A 1994. [DOI: 10.1016/0021-9673(94)80402-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Yang SK. Acid-catalyzed stereoselective heteronucleophilic substitution and racemization of 3-O-methyloxazepam and 3-O-ethyloxazepam. Chirality 1994; 6:175-84. [PMID: 8024948 DOI: 10.1002/chir.530060304] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Enantiomers of 3-O-methyloxazepam (MeOX) and 3-O-ethyloxazepam (EtOX) were resolved by chiral stationary phase high-performance liquid chromatography (CSP-HPLC). Reaction kinetics and deuterium isotope effects of acid-catalyzed racemization of enantiomeric MeOX in ethanol and enantiomeric EtOX in methanol were studied by spectropolarimetry. The acid-catalyzed heteronucleophilic substitution reactions of racemic MeOX in ethanol and racemic EtOX in methanol were studied by reversed-phase HPLC. Thermodynamic parameters involved in the reactions were obtained by temperature-dependent reaction rates. The effects of solvent's dielectric constant on the heteronucleophilic substitution reactions were also determined. A nucleophilically solvated and transient C3 carbocation intermediate resulting from an N4-protonated enantiomer, derived from a 1,4-benzodiazepine either in M (minus) or P (plus) conformation, is proposed to be an intermediate and responsible for the acid-catalyzed stereoselective nucleophilic substitution and the resulting racemization.
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Affiliation(s)
- S K Yang
- Department of Pharmacology, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland
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25
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Shimada J, Hori S, Oguma T, Yoshikawa T, Yamamoto S, Nishikawa T, Yamada H. Effects of protein binding on the isomerization of ceftibuten. J Pharm Sci 1993; 82:461-5. [PMID: 8360822 DOI: 10.1002/jps.2600820506] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Isomerization of ceftibuten to trans-ceftibuten, a less active isomer of ceftibuten, was observed in human serum in vitro. Investigation of the isomerization mechanism in the serum clarified that albumin accelerated the isomerization. The isomerization rate constant correlated significantly with the percent of binding to albumin, suggesting the binding of ceftibuten to albumin might be the driving force for the isomerization under in vitro conditions. This isomerization was also observed in clinical studies in humans. Results of physiological model analysis indicate that the isomerization catalyzed by albumin contributes significantly to the overall isomerization in the human body following oral administration.
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Affiliation(s)
- J Shimada
- Institute of Medical Science, St. Marianna University School of Medicine, Kawasaki, Japan
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26
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Witte DT, Ensing K, Franke JP, De Zeeuw RA. Development and registration of chiral drugs. PHARMACY WORLD & SCIENCE : PWS 1993; 15:10-6. [PMID: 8485501 DOI: 10.1007/bf02116164] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In this review we describe the impact of chirality on drug development and registration in the United States, Japan and the European Community. Enantiomers may have differences in their pharmacological profiles, and, therefore, chiral drugs ask for special analytical and pharmacological attention during their development. However, the registration authorities have no clear policy towards the registration of chiral drugs. The absence of a clear policy regarding chirality causes a great deal of confusion and frustration at various levels and is not in the interest of industries developing newer and more beneficial drugs.
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Affiliation(s)
- D T Witte
- Department of Analytical Chemistry and Toxicology, University Centre for Pharmacy, Groningen, The Netherlands
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27
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Fujimaki Y, Sudo K, Hakusui H. Pharmacokinetics of nefiracetam and three metabolites in humans and stereoselective hydroxylation of its pyrrolidine ring. Xenobiotica 1993; 23:61-70. [PMID: 8484264 DOI: 10.3109/00498259309059362] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
1. The kinetics of nefiracetam (I) and three metabolites (II-IV) were investigated in healthy volunteers. Compounds I-IV in serum and urine were measured by h.p.l.c. 2. After a single 200 mg dose of nefiracetam the drug was absorbed rapidly and showed peak serum levels of 16.3 +/- 0.9 nmol/ml. Cmax values of the three metabolites were comparatively low (0.96-4.89 nmol/ml), and tmax and t1/2 values of the metabolites (4.1-9.6 h and 7.8-21.9 h, respectively) were longer than those of I (1.6 h and 3.9 h respectively). Urinary excretion of I in 24 h was about 5% of the dose. The major urinary metabolite, a pyrrolidine ring scission product (IV), had a mean total excretion of 17.8% dose. The total of all four compounds in urine amounted to 43.4% dose. 3. In a multiple-dose study (daily 3 x 200 mg doses of nefiracetam for 7 days), the serum concentration profile of each compound indicated that the steady state was reached in 7 days. 4. Metabolite II existed as a racemate and III mainly as the (-)-enantiomer in human urine.
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Affiliation(s)
- Y Fujimaki
- Drug Metabolism and Analytical Chemistry Research Center, Daiichi Pharmaceutical Co. Ltd., Tokyo, Japan
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Testa B, Carrupt PA, Gal J. The so-called "interconversion" of stereoisomeric drugs: an attempt at clarification. Chirality 1993; 5:105-11. [PMID: 8338720 DOI: 10.1002/chir.530050302] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A variety of reactions can be categorized under the global concept of the "interconversion of stereoisomers." Thus, racemization or epimerization can result from inversion of labile chiral centers. From the examples available, some predictive rules are suggested for a chiral center of the type R"R'RC-H undergoing base-catalyzed inversion and a provisional table of affecting groups is presented. Unimolecular inversion of nonsymmetrical, nonplanar ring systems can also result in racemization or epimerization, but no generalization can yet be offered. Beside these cases of nonenzymatic reactions, a limited variety of enzymatic reactions can operate to interconvert stereoisomers, the outcome rarely being a racemic mixture. An important aspect of stereoisomer interconversion is the time scale in which the phenomenon is observed. Thus, several reactions to nonezymatic racemization or epimerization are fast compared to the duration of action of the drug and therefore have pharmacological significance, while other are slower and are of pharmaceutical relevance only.
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Affiliation(s)
- B Testa
- Institute of Medicinal Chemistry, School of Pharmacy, University of Lausanne, Switzerland
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Yang SK, Lu XL. Acid-Catalyzed nucleophilic substitution and racemization of 3-methoxy-N-desmethyldiazepam enantiomers in methanol. Chirality 1993. [DOI: 10.1002/chir.530050209] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Wännman H, Walhagen A, Erlandsson P. Practical approach to the miniaturization of chiral separations in liquid chromatography using packed fused-silica capillary columns. J Chromatogr A 1992. [DOI: 10.1016/0021-9673(92)85352-t] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Walhagen A, Edholm LE. Chiral separation on achiral stationary phases with different functionalities using β-cyclodextrin in the mobile phase and application to bioanalysis and coupled columns. Chromatographia 1991. [DOI: 10.1007/bf02276243] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Affiliation(s)
- B Testa
- Institut de Chimie thérapeutique, Ecole de Pharmacie, Université de Lausanne, CH-1005, Switzerland
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Simonyi M, Gal J, Testa B. Signs of the times: the need for a stereochemically informative generic name system. Trends Pharmacol Sci 1989; 10:349-54. [PMID: 2690425 DOI: 10.1016/0165-6147(89)90006-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
'Research and clinical pharmacologists frequently present data on impure drugs.' Because generic drug names often hide the fact that different stereoisomers (possibly with different pharmacological properties) may be present in the 'pure' preparation, this statement is all too frequently true. However, the problem may be overcome by pharmacologists and publishers adopting the user-friendly SIGNS nomenclature devised and explained here by Miklòs Simonyi, Joseph Gal and Bernard Testa. The acronym stands for 'stereochemically informative generic name system'. Seven prefixes are offered to describe the stereochemical nature of any drug. The appropriate prefix would be attached to the generic name. A generic name without prefix would indicate a single agent with no stereoisomers.
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