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Influence of CYP2D6 genotype on the disposition of the enantiomers of venlafaxine and its major metabolites in postmortem femoral blood
Linköping University, Department of Medical and Health Sciences, Clinical Pharmacology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Medical and Health Sciences, Clinical Pharmacology. Linköping University, Faculty of Health Sciences.
National Board of Forensic Medicine, Linköping, Sweden.
Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Health Sciences. National Board of Forensic Medicine, Linköping, Sweden.
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2012 (English)In: Forensic Science International, ISSN 0379-0738, E-ISSN 1872-6283, Vol. 214, no 1-3, 124-134 p.Article in journal (Refereed) Published
Abstract [en]

Venlafaxine (VEN) is an antidepressant drug mainly metabolized by the cytochrome P450 (CYP) enzyme CYP2D6 to the active metabolite O-desmethylvenlafaxine (ODV). VEN is also metabolized to N-desmetylvenlafaxine (NDV) via CYP3A4. ODV and NDV are further metabolized to N,O-didesmethylvenlafaxine (DDV). VEN is a racemic mixture of the S- and R-enantiomers and these have in vitro displayed different degrees of serotonin and noradrenaline reuptake inhibition. The aim of the study was to investigate if an enantioselective analysis of VEN and its metabolites, in combination with genotyping for CYP2D6, could assist in the interpretation of forensic toxicological results in cases with different causes of deaths. Concentrations of the enantiomers of VEN and metabolites were determined in femoral blood obtained from 56 autopsy cases with different causes of death. The drug analysis was done by liquid chromatography tandem mass spectrometry (LC/MS/MS) and the CYP2D6 genotyping by PCR and pyrosequencing. The mean (median) enantiomeric S/R ratios of VEN, ODV, NDV and DDV were 0.99 (0.91), 2.17 (0.93), 0.92 (0.86) and 1.08 (1.03), respectively. However, a substantial variation in the relationship between the S- and R-enantiomers of VEN and metabolites was evident (S/R ratios ranging from 0.23 to 17.6). In six cases, a low S/R VEN ratio (mean 0.5) was associated with a high S/R ODV ratio (mean 11.9). Genotyping showed that these individuals carried two inactive CYP2D6 genes indicating a poor metabolizer phenotype. From these data we conclude that enantioselective analysis of VEN and ODV can predict if a person is a poor metabolizer genotype/phenotype for CYP2D6. Knowledge of the relationship between the S- and R-enantiomers of this antidepressant drug and its active metabolite is also important since the enantiomers display different pharmacodynamic profiles.

Place, publisher, year, edition, pages
Elsevier , 2012. Vol. 214, no 1-3, 124-134 p.
Keyword [en]
CYP2D6; Enantiomers; Forensic toxicology; Postmortem toxicology; Venlafaxine
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-72238DOI: 10.1016/j.forsciint.2011.07.034ISI: 000298634900032PubMedID: 21840145OAI: oai:DiVA.org:liu-72238DiVA: diva2:458654
Note

Funding agencies|Forensic Science Center of Linkoping University||National Board of Forensic Medicine in Sweden||Swedish Research Council| 2009-4740 |

Available from: 2011-11-23 Created: 2011-11-23 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Genetic influence on enantiomeric drug disposition: Focus on venlafaxine and citalopram
Open this publication in new window or tab >>Genetic influence on enantiomeric drug disposition: Focus on venlafaxine and citalopram
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A molecule that is not identical to its mirror image is said to be chiral. A racemic mixture, or a racemate, is one that has equal amounts of S- and R-enantiomers of a chiral molecule. Two examples of frequently prescribed racemic drugs are the antidepressants venlafaxine (VEN) and citalopram (CIT). The R-enantiomer of VEN is a potent inhibitor of serotonin and noradrenaline reuptake, while the S-enantiomer is more selective in inhibiting serotonin reuptake. CIT is a selective serotonin reuptake inhibitor and the S-enantiomer is responsible for this effect. The R-enantiomer of CIT is therapeutically inactive, but displays other effects or side-effects. Due to the potential of different pharmacological and toxicological activities of the VEN and CIT enantiomers, it is of great interest to investigate the individual enantiomers of these drugs, concerning both pharmacokinetics and pharmacodynamics. For this purpose, it is necessary to develop stereoselective bioanalytical methods. A major clinical problem in the use of many drugs is the inter-individual variability in drug metabolism and response. Genetic variations contribute to this variability, including e.g. polymorphisms in the cytochrome P450 (CYP) enzymes. Approximately 7% of all Caucasians lack the polymorphic isoenzyme CYP2D6 and these individuals are classified as poor metabolisers. Both VEN and CIT are partly metabolised by CYP2D6. However, it is not completely known how CYP2D6 deficiency may influence the in vivo pharmacokinetics of these drugs, especially regarding the enantiomeric disposition. The overall aim of this thesis was to study the relationship between pharmacokinetics and pharmacogenetics for VEN and CIT, with emphasis on enantiomeric drug disposition in different biomatrices. In Paper I, a validated liquid chromatography-tandem mass spectrometry (LC/MS/MS) method for enantioselective determination of VEN and its three major metabolites was developed and applied in plasma from patients and whole blood samples from forensic autopsy cases. In Papers II and III, the genetic influence on enantiomeric drug disposition in serum and brain following administration of racemic CIT and VEN to Sprague-Dawley and Dark Agouti rats was studied. The female Sprague-Dawley and Dark Agouti rats are considered the animal counterparts of the human extensive and poor metaboliser CYP2D6 phenotypes, respectively. Significant quantitative strain-related differences in the pharmacokinetics of CIT and VEN, and their metabolites, were observed. The results indicate that the CYP2D enzymes display a significant impact on the stereoselective metabolism of these drugs. The findings also highlight the importance of comparing different rat strains when conducting experimental pharmacokinetic studies. In Paper IV, the relation between CYP2D6 genotype and the disposition of the enantiomers of VEN and its metabolites in femoral blood from forensic autopsy cases was studied. A substantial variation in the relationship between the S- and R-enantiomers of VEN, and metabolites, was found. In individuals lacking two functional CYP2D6 alleles, a low enantiomeric S/R VEN ratio was strongly related to a high S/R ratio for the main metabolite O-desmethylvenlafaxine. Hence, by using enantioselective analysis of VEN and O-desmethylvenlafaxine, it is possible to predict if a person is a poor metaboliser genotype/phenotype for CYP2D6.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 91 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1264
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-72240 (URN)9789173930574 (ISBN)
Public defence
2011-12-15, Berzeliussalen, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 13:00 (Swedish)
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Available from: 2011-11-23 Created: 2011-11-23 Last updated: 2017-12-12Bibliographically approved

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Kingbäck, MariaKarlsson, LouiseZackrisson, Anna-LenaJosefsson, MartinCarlsson, BjörnBengtsson, FinnAhlner, JohanKugelberg, Fredrik C

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