Document Detail

The role of cytochrome P450 2C19 activity in flunitrazepam metabolism in vivo.
MedLine Citation:
PMID:  12640218     Owner:  NLM     Status:  MEDLINE    
Flunitrazepam, a hypnotic benzodiazepine, is widely prescribed around the world for the treatment of insomnia and as a preanesthetic. In vitro studies have shown that the metabolism of flunitrazepam to desmethylflunitrazepam and 3-hydroxyflunitrazepam is mediated in part by the polymorphic enzyme CYP2C19. The objective was to examine the role of CYP2C19 activity in determining flunitrazepam kinetics in vivo. Sixteen healthy volunteers (14 genotypic extensive metabolizers and 2 poor metabolizers) were recruited who had a wide range of CYP2C19 activity (0.50-28.8), as determined by the omeprazole/ 5-hydroxyomeprazole ratio (OMR) at 3 hours following administration of omeprazole, 20 mg orally. Each subject received flunitrazepam, 1 mg orally. Blood samples were collected immediately before and up to 48 hours after drug administration and were assayed by HPLC for flunitrazepam and its metabolites, 7-aminoflunitrazepam, desmethylflunitrazepam, and 3-hydroxyflunitrazepam. Spearman correlations were determined for OMR and pharmacokinetic parameters. With increasing OMR (decreasing CYP2C19 activity), the ratio of flunitrazepam to both desmethylflunitrazepam and 3-hydroxyflunitrazepam AUCs increased ( r = 0.55, p = 0.03 and r = 0.65, p = 0.01, respectively). However, variation in CYP2C19 activity did not significantly affect the AUCs of flunitrazepam or its metabolites. The authors conclude that CYP2C19 contributes to the metabolism of flunitrazepam to desmethylflunitrazepam and 3-hydroxyflunitrazepam in vivo, but these data suggest that its role is minor and that differences in CYP2C19 activity do not likely substantially influence its clinical effects.
I Gafni; U E Busto; R F Tyndale; H L Kaplan; E M Sellers
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of clinical psychopharmacology     Volume:  23     ISSN:  0271-0749     ISO Abbreviation:  J Clin Psychopharmacol     Publication Date:  2003 Apr 
Date Detail:
Created Date:  2003-03-17     Completed Date:  2003-08-01     Revised Date:  2013-08-12    
Medline Journal Info:
Nlm Unique ID:  8109496     Medline TA:  J Clin Psychopharmacol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  169-75     Citation Subset:  IM    
Institute of Medical Science, dagger Faculty of Pharmacy, double dagger Department of Pharmacology and section sign University of Toronto, Toronto, Canada.
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MeSH Terms
Anti-Anxiety Agents / blood,  pharmacokinetics*
Area Under Curve
Aryl Hydrocarbon Hydroxylases / metabolism*
Chromatography, High Pressure Liquid
Flunitrazepam / analogs & derivatives*,  blood,  pharmacokinetics*
Middle Aged
Mixed Function Oxygenases / metabolism*
Grant Support
Reg. No./Substance:
0/Anti-Anxiety Agents; 055XLQ0YQ6/N-desmethylflunitrazepam; 1622-62-4/Flunitrazepam; 34084-50-9/7-aminoflunitrazepam; 67739-71-3/3-hydroxyflunitrazepam; EC 1.-/Mixed Function Oxygenases; EC Hydrocarbon Hydroxylases; EC protein, human

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