Quazepam pharmacokinetics

The effects of itraconazole 100 mg/day for 14 days on the pharmacokinetics of a single oral dose of quazepam 20 mg and its two active metabolites have been studied in 10 healthy men in a double-blind, randomized, placebo-controlled crossover study (3). Itraconazole did not change the pharmacokinetics of quazepam but significantly reduced the peak plasma concentration and AUC of 2-oxoquazepam and N-desalkyl-2-oxoquazepam. Itraconazole did not affect psychomotor function. The results suggested that CYP3A4 is partly involved in the metabolism of quazepam. 

Yasui-Furukori N, Kondo T, Takahata T, Mihara K, Ono S, Kaneko S, Tateishi T. Effect of dietary fat content in meals on pharmacokinetics of quazepam. J Clin Pharmacol 2002 42(12) 1335-40. 

Hilbert JM, Battista D. Quazepam and flurazepam differential pharmacokinetic and pharmacodynamic characteristics. J Clin Psychiatry 1991 52(Suppl) 21-6. 

Ankier SI, Goa KL. Quazepam. A preliminary review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in insomnia. Drugs 1988 35 42-62. 

The choice of a particular benzodiazepine is based on its pharmacokinetic profile. When used as a single dose, the extent of distribution and elimination half-life is important in predicting the duration of action. However, after multiple dosing, the elimination half-life and formation of active metabolites determine the extent of drug accumulation and resultant clinical effects." The benzodiazepine pharmacokinetic profiles are summarized in Table 71-4. The onset of action depends on the rate of absorption. Flurazepam and triazolam are absorbed rapidly. Temazepam is less lipophilic and has a slower onset of effect. Sedation after flurazepam, estazolam, and quazepam occurs within 1 to 2 hours after ingestion." Triazolam is redistributed quickly because of its high lipophilicity and thus has a short duration of effect." Estazolam and temazepam are intermediate in their duration of action. The therapeutic effects of flurazepam and quazepam are long in comparison because of the active metabolites. 

Table 19.1. Some Properties and Pharmacokinetics of the Benzodiazepine Sedatix Parameters Estazolam Flurazepam Quazepam Temazepam...

In a placebo-controlled study in 12 healthy subjects it was found that fluvoxamine 25 mg twice daily for 14 days had no effect on the pharmacokinetics of a single 20-mg dose of quazepam. However, formation of the metabolite 2-oxoquazepam was decreased, and there was a minor deerease in the sedative effects of quazepam at 4 hours, although these ehanges were considered to be of little clinical significance. ... 

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