AIM:To examine whether the sedative effects assessed by psychomotor tests would depend on the cytochrome P450(CYP)2C19 genotypes after an infusion regimen of diazepam commonly used for gastrointestinal endoscopy in Japan.METHODS:Fifteen healthy Japanese volunteers consisting of three different CYP2C19 genotype groups underwent a critical flicker fusion test,an eye movement analysis and a postural sway test as a test for physical sedative effects,and a visual analog scale(VAS)symptom assessment method as a test for mental sedative effects during the 336 h period after the intravenous infusion of diazepam(5 mg).RESULTS:The physical sedative effects assessed by the critical flicker test continued for 1h(t values of 5 min,30 min and 60 min later:4.35,5.00 and 3.19,respectively)and those by the moving radial area of a postural sway test continued for 3h(t values of 5 h,30 h,60 min and 3 h later:-4.05,-3.42,-2.17 and -2.58,respectively),which changed significantly compared with the baseline level before infusion(P＜0.05).On the other hand,the mental sedative effects by the VAS method improved within 1 h.The CYP2C19 genotype-dependent differences in the postinfusion sedative effects were not observed in any of the four psychomotor function tests.CONCLUSION:With the psychomotor tests,the objective sedative effects of diazepam continued for 1 h to 3 h irrespective of CYP2C19 genotype status and the subjective sedative symptoms improved within 1 h.Up to 3 h of clinical care appears to be required after the infusion of diazepam,although patients feel subjectively improved.(C)2008 The W3G Press,All rights reserved.