Induction of cytochrome P450 2B6 activity by the herbal medicine baicalin as measured by bupropion hydroxylation

This study investigated the effect of the herbal medicine baicalin on bupropion hydroxylation, a probe reaction for CYP2B6 activity related to different CYP2B6 genotype groups. Seventeen healthy male volunteers (6 CYP2B6*1/*1, 6 CYP2B6*1/*6, and 5 CYP2B6*6/*6) received orally administered bupropion alone and during daily treatment with baicalin. Blood samples were taken up to 72 h after each bupropion dose, and pharmacokinetics profiles were determined on days 1 and 25 for bupropion and hydroxybupropion. Baicalin administration increased hydroxybupropion maximum plasma concentration (C (max)) by 73% [90% confidence interval (CI), 44-108%; P < 0.01] and the area under the concentration time curve extrapolated to infinity (AUC(0-az)) of hydroxybupropion by 87% (90% CI, 48-137%; P < 0.01), with no change in the elimination half-life of hydroxybupropion. Baicalin increased the AUC(0-az) ratio of hydroxybupropion to bupropion by 63% (90% CI, 38-92%; P < 0.01). Baicalin significantly induced CYP2B6-catalyzed bupropion hydroxylation, and the effects of baicalin on other CYP2B6 substrate drugs deserve further investigation.