The effects of Ginkgo biloba leaf extract (GBE) on the pharmacokinetics and pharmacodynamics of nifedipine (NFP), a calcium-channel blocker, were studied using eight healthy volunteers. Simultaneous oral ingestion of GBE (240 mg) did not significantly affect any of the mean pharmacokinetic parameters of either NFP or dehydronifedipine, a major metabolite of NFP, after oral administration of NFP (10 mg). However, the maximal plasma NFP concentrations in two subjects were approximately doubled by GBE, and they had more severe and longer-lasting headaches with GBE than without GBE, with dizziness or hot flushes in combination with GBE.