Comparative pharmacokinetics and bioavailability of flavonoid glycosides of Ginkgo biloba after a single oral administration of three formulations to healthy volunteers.

Eighteen healthy volunteers received three different formulations of Ginkgo biloba: capsules (A) and drops (B) (delivered by Agon Pharma), and tablets (C) (Tebonin-Dr. W. Schwabe) in equal an quantity, orally as a single dose, at an interval of at least five days. The pharmacokinetic parameters of the most important flavonoid glycosides: quercetin, kaempferol and isorhamnetin were established. The bioavailability was estimated using capsules as a standard formulation. Only the time to reach the peak concentration (tmax) of quercetin, kaempforol and isorhamnetin administered in the form of capsules, was significantly prolonged as compared with drops and tablets. Area under the curve (AUC) was the largest for formulation B for all the evaluated flavonoid glycosides, however the differences were not statistically significant. It is concluded that the three formulations of Ginkgo biloba extract are bioequivalent.