Abstract: AIM: To examine the potential effects of genistein on CYP3A activity. METHODS: The experiment was conducted in an open, randomized, 2-period crossover study. The probe drug midazolam was used as an indicator of CYP3A function. Every volunteer was administered orally, once a day for 14 days, genistein 1000 mg or placebo(control).On 15th day, a 7.5 mg midazolam was administrated orally. The plasma concentration of midazolam, 1-OH midazolam was determined over 36 h. RESULTS: Coadministration of genistein obviously decreased the area under the curve AUC_0-36 of midazolam [(144±55) ng·mL^-1·h vs (126±40) ng·mL^-1·h,P<0.05] , and significantly decreased AUC_0-∝ of midazolam[(209±57) vs (181±43) ng·mL^-1·h,P<0.05] ,and also decreased C_max of midazolam[(49±20) vs (36±14),P<0.05] . CONCLUSION: Genistein, a principal isoflavone in soybean, in regular doses may induce CYP3A activity in vivo, and it should be aware of potential drug-food interactions.

Key words: Genistein, CYP3A activity, Pharmacokinetics