A critical review of 40 published clinical trials (up to the end of 1990) using
an orally administered G. biloba extract in the treatment of cerebral insufficiency
concluded that only eight of the studies were well performed (21, 22). Almost
all trials reported at least a partially positive response at dosages of 120–160mg
a day (standardized extract) and treatment for at least 4–6 weeks (21, 22).
In a comparison of G. biloba with published trials using co-dergocrine
(dihydroergotoxine), a mixture of ergoloid mesilates used for the same purpose,
both G. biloba extract and co-dergocrine showed similar efficacy. A direct
comparison of 120mg of G. biloba standardized extract and 4.5mg codergocrine
showed similar improvements in both groups after 6 weeks (84).
A meta-analysis of 11 placebo-controlled, randomized double-blind studies
in elderly patients given G. biloba extract (150 mg orally per day) for cerebral
insufficiency concluded that eight studies were well performed (85). Significant
differences were found for all analysed single symptoms, indicating the superiority
of the drug in comparison with the placebo. Analysis of the total score of
clinical symptoms indicated that seven studies confirmed the effectiveness of G.
biloba extract, while one study was inconclusive (85).