Absorption

In humans, absolute bioavailability is 98-100% for ginkgolide A, 7993% for ginkgolide B, and at least 70% for bilobalide (36). In two healthy volunteers, flavonol glycosides administered as the product LI 1370 at doses of 50, 100, and 300 mg were absorbed in the small intestine with peak plasma concentration attained within 2-3 hours (19). Additional data from human experiments from the manufacturer of 80-mg EGb 761 solution show that the absolute bioavailabilities of ginkgolides A and B were greater than 80%, whereas that of ginkgolide C was very low. Bioavailability of bilobalide was 70% after administration of 120 mg of the extract. Corroborating these results was a later pharmacokinetic study (52) that found mean bioavailabilities of 80, 88, and 79% for ginkgolide A, ginkgolide B, and bilobalide, respectively. Food intake did increase the time to peak concentration, but did not affect bioavailability.

A study in rats using radiolabeled EGb 761 revealed a bioavailability of at least 60% (19). Peak blood concentrations occurred at 1.5 hours. At 3 hours, the highest radioactivity was measured in the stomach and small intestine, indicating that these are the sites of absorption.

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