Effects of Seijo‐bofu‐to, a Traditional Japanese Herbal Medicine Containing Furanocoumarin Derivatives, on the Drug‐Metabolizing Enzyme Activities in Healthy Male Volunteers

Seijo-bofu-to, a traditional medicine used to treat acne in Asian countries, contains twelve herbal components, including Angelica dahurica root, a source of furanocoumarin derivatives. In this study, we investigated potential herb–drug interactions of seijo-bofu-to in healthy male volunteers. Thirty-two young, healthy, non-smoking males were assessed for the baseline activity of cytochrome P450 (CYP) 1A2, CYP3A, CYP2D6, N-acetyltransferase 2 and xanthine oxidase according to the urinary metabolic indices of 8-hr urine samples collected after the administration of a 150-mg dose of caffeine and a 30-mg dose of dextromethorphan, and the ratio of urinary excretion of 6β-hydroxycortisol to cortisol. Thereafter, the volunteers received 3.75 g of seijo-bofu-to twice daily for 7 days and underwent the same tests on post-dose day 7. The geometric mean ratio of the CYP1A2 activity on day 7 to that observed at baseline was 0.66 (95% CI, 0.55–0.79, p = 0.001). The geometric mean phenotypic indices for CYP3A, CYP2D6, N-acetyltransferase 2 and xanthine oxidase on day 7 did not differ from the baseline values. The findings of the present study suggest that seijo-bofu-to may inhibit the activity of CYP1A2, whereas it is unlikely to participate in herb–drug interactions involving medications predominantly metabolized by CYP3A, CYP2D6, N-acetyltransferase 2 or xanthine oxidase.