Studies on Interactions between Functional Foods or Dietary Supplements and Medicines. III. Effects of Ginkgo biloba Leaf Extract on the Pharmacokinetics of Nifedipine in Rats

The effects of Ginkgo biloba leaf extract (GBE), one of the most widely used herbal dietary supplements in Japan and the United States, on the pharmacokinetics of nifedipine (NFP), a typical probe of P450 (CYP) 3A, but not a substrate of the multidrug transporter P-glycoprotein (P-gp), were studied using rats. Simultaneous oral treatment with GBE (20 mg/kg) did not affect the pharmacokinetics after intravenous administration of NFP (2.5 mg/kg). However, the maximal plasma NFP concentration, the area under the concentration–time curve and absolute bioavailability after oral administration of NFP (5 mg/kg) were significantly increased by simultaneous oral treatment with GBE, approximately 1.6-fold, 1.6-fold and 2.1-fold, respectively. These results suggest that the concomitant oral use of GBE appeared to reduce the first-pass metabolism of orally administered NFP, by inhibiting CYP3A, possibly but not P-gp, in rats.