title: Single oral dose pharmacokinetics of quazepam is influenced by CYP2C19 activity.
abstract: The effects of cytochrome P450 (CYP)2C19 activity and cigarette smoking on the single oral dose pharmacokinetics of quazepam were studied in 20 healthy Japanese volunteers. Twelve subjects were extensive metabolizers (EMs), and 8 subjects were poor metabolizers (PMs) by CYP2C19 as determined by the PCR-based genotyping. Nine subjects were smokers (>10 cigarettes/d), and 11 subjects were nonsmokers. The subjects received a single oral 20-mg dose of quazepam, and blood samplings and evaluation of psychomotor function were conducted up to 72 hours after dosing. Plasma concentrations of quazepam and its active metabolite 2-oxoquazepam (OQ) were measured by HPLC. There were significant differences between EMs and PMs in the peak plasma concentration (mean +/- SD: 34.5 +/- 16.6 versus 66.2 +/- 19.2 ng/mL, P < 0.01) and total area under the plasma concentration-time curve (490.1 +/- 277.5 vs 812.1 +/- 267.2 ng x h/mL, P < 0.05) of quazepam. The pharmacokinetic parameters of OQ and pharmacodynamic parameters were not different between the 2 groups. Smoking status did not affect the pharmacokinetic parameters of quazepam and OQ or pharmacodynamic parameters. The present study suggests that the single oral dose pharmacokinetics of quazepam are influenced by CYP2C19 activity but not by cigarette smoking.
authors.affiliation: Department of Neuropsychiatry, Yamagata University School of Medicine, Yamagata, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Fukasawa
authors.forename: Norio
authors.initials: N
authors.lastname: Yasui-Furukori
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Aoshima
authors.forename: Akihito
authors.initials: A
authors.lastname: Suzuki
authors.forename: Tomonori
authors.initials: T
authors.lastname: Tateishi
authors.forename: Koichi
authors.initials: K
authors.lastname: Otani
mesh_terms: D000328:Adult; D019540:Area Under Curve; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism*; D044466:Asian People; D001569:Benzodiazepines / Q000493:pharmacokinetics* / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D065731:Cytochrome P-450 CYP2C19; D005260:Female; D005838:Genotype; D006207:Half-Life; D006801:Humans; D006993:Hypnotics and Sedatives / Q000493:pharmacokinetics* / Q000494:pharmacology; D007564:Japan; D008297:Male; D008657:Metabolic Clearance Rate; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D012907:Smoking / Q000378:metabolism*
chemical_list: D006993:Hypnotics and Sedatives; D001569:Benzodiazepines; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; C025130:quazepam