Time effects of food intake on the pharmacokinetics and pharmacodynamics of quazepam

Abstract

Aims: There is little information on interaction between food and the hypnotic agent quazepam. We therefore studied the effects of food and its time interval on the pharmacokinetics and pharmacodynamics of quazepam.

Methods: A randomized three-phase crossover study with 2-week intervals was conducted. Nine healthy male volunteers took a single oral 20 mg dose of quazepam under the following conditions: 1) after fasting overnight; 2) 30 min after eating standard meal; or 3) 3 h after eating the same meal. Plasma concentrations of quazepam and its metabolite, 2-oxoquazepam and psychomotor function using the Digit Symbol Substitute Test (DSST), Stanford Sleepiness Scale (SSS) and Visual Analogue Scale were measured up to 48 h.

Results: During the food treatments at 30 min and 3 h before dosing, the peak concentrations (Cmax) were 300% (95% CI 260, 340%; P < 0.001) and 250% (95% CI 210, 290%; P < 0.01) of the corresponding value during the fasting phase. For quazepam, the area under the plasma concentration-time curve from 0 to 8 h measured at 30 min and 3 h before dosing was significantly increased, with the food treatments by 2.4-fold (95% CI 2.0; 2.8-fold; P < 0.001) and 2.1-fold (95% CI 1.7; 2.4-fold; P < 0.01), respectively. In response to pharmacokinetic changes, some of the pharmacodynamics (DSST, P < 0.05; SSS, P < 0.05) differed significantly between fasted status and fed status. No difference was found in any pharmacokinetic or pharmacodynamic parameters between the two food treatment phases.

Conclusions: A food effect on quazepam absorption is evident and continues at least until 3 h after food intake. The dosing of quazepam after a long period of ordinary fasting might reduce its efficacy because a 3 h interval between the timing of the evening meal and bedtime administration of hypnotics is regarded as normal in daily life.

Figure 1

The geometric mean plasma quazepam concentration-time curve from 0 to 48 h (a) and the mean plasma 2-oxoquazepam concentration–time curve from 0 to 24 h (b) after a single oral dose of 20 mg quazepam to nine healthy volunteers. ○, variables with no food; •, variables at 30 min after food intake and ▵, variables at 3 h after food intake.

Figure 2

The median score of change in Digit Symbol Substitution Test (DSST)–time curve (a), the mean Stanford Sleepiness Score (SSS)– time curve (b), the mean scale in item ‘thinking speed’ in Visual Analogue Scale (VAS)–time curve (c) and the mean scale in item ‘fatigue’ in VAS–time curve (d) from 0 to 48 h after a single oral dose of 20 mg quazepam to nine healthy volunteers. ○, variables with no food; •, variables at 30 min after food intake and ▵, variables at 3 h after food intake.