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Interaction between grapefruit juice and hypnotic drugs: comparison of triazolam and quazepam

Interaction between grapefruit juice and hypnotic drugs: comparison of triazolam and quazepam

  1. RaverHippie
    Koh-ichi Sugimoto, Nobutaka Araki, Masami Ohmori, Ken-ichi Harada, Yimin Cui, Shuichi Tsuruoka, Atsuhiro Kawaguchi and Akio Fujimura
    (1) Division of Clinical Pharmacology, Department of Pharmacology, Jichi Medical School, 3311-1 Minamikawachi, Tochigi 329-0498, Japan Received: 17 October 2005 Accepted: 14 November 2005 Published online: 17 January 2006



    Abstract Objective: Grapefruit juice (GFJ) inhibits cytochrome P450 (CYP) 3A4 in the gut wall and increases blood concentrations of CYP3A4 substrates by the enhancement of oral bioavailability. The effects of GFJ on two benzodiazepine hypnotics, triazolam (metabolized by CYP3A4) and quazepam (metabolized by CYP3A4 and CYP2C9), were determined in this study.

    Methods: The study consisted of four separate trials in which nine healthy subjects were administered 0.25 mg triazolam or 15 mg quazepam, with or without GFJ. Each trial was performed using an open, randomized, cross-over design with an interval of more than 2 weeks between trials. Blood samples were obtained during the 24-h period immediately following the administration of each dose. Pharmacodynamic effects were determined by the digit symbol substitution test (DSST) and utilizing a visual analog scale.

    Results GFJ increased the plasma concentrations of both triazolam and quazepam and of the active metabolite of quazepam, 2-oxoquazepam. The area under the curve (AUC)(0–24) of triazolam significantly increased by 96% (p