The pharmacological effects of ginkgo biloba, a plant extract, on the brain of dementia patients in comparison with tacrine.

In 1994, a standardized dry extract of Ginkgo biloba leaves (SeGb), has been approved by German health authorities for the treatment of primary degenerative dementia and vascular dementia. More than 24 different brands of Ginkgo biloba extract are sold in the United States. Tacrine, also known as tetrahydroaminoacrine (THA), and donepezil are currently the only drugs approved in the United States for the treatment of Alzheimer's disease. Previous studies demonstrated that SeGb and tacrine induce significant pharmacological effects on the brains of young, healthy human males, as determined by bioelectrical activity measurements obtained using the quantitative pharmaco-electroencephalogram (QPEEG) method. The type of central nervous system (CNS) effects we have seen on computer-analyzed EEGs (CEEGs) after administration of tacrine or EGb suggests both are "cognitive activators" which are, as a class of products, characterized by a (prepost) relative increase of 7.5 to 13 Hz ("alpha") and decrease of 1.3 to 7.5 Hz ("delta" and "theta") activity. To determine whether EGb or tacrine had noticeable pharmacological effects on elderly subjects diagnosed with possible or probable Alzheimer's, the present open, uncontrolled trial was conducted. Data from 18 subjects (11 males, 7 females) at an average age of 67.4 years with light to moderate dementia (Mini Mental mean score = 23.7, ranges: 15-29 [Geriatric Depression Scale mean scores = 3.7; range: 3.2-5.4]) were analyzed for this presentation. Each subject was randomly administered a single oral "Test-Dose" of either 40 mg of tacrine or 240 mg of EGb2 in two separate sessions within 3- to 7-day intervals. Before drug administration and at 1- and 3-hour intervals after drug administration, CEEGs were recorded for a minimum of 10 minutes. The CEEGs were analyzed using Period Analysis programs we developed for QPEEG. The results indicated that both EGb and, to a lesser degree, tacrine induced pharmacological effects, as established by QPEEG measurements, in the CNS similar to those previously established in healthy, young subjects. The type of CNS effects produced by EGb (as established by HZI's CEEG psychotropic drug database) in elderly dementia patients were similar to those induced by tacrine responders as well as those seen after the administration of other "cognitive activators" (pramiracetam, vinpocetine, BMY-21502, suloctidil, and lisuride) and anti-dementia drugs approved in the United States or Europe (tacrine, donepezil, nimodipine, piracetam, and oxiracetam) from our database. The results also showed that 240 mg of EGb has typical cognitive activator CEEG profiles (responders) in more subjects (8 of 18) than 40 mg tacrine (3 of 18 subjects). Because of the small sample size, we could not test the hypothesis that subjects who showed cognitive activator-type pharmacological response to the first Test-Dose of EGb or tacrine also exhibit more therapeutic effects (compared to nonresponders) when drugs are administered chronically.