Clinical efficacy of Ginkgo biloba special extract EGb 761 in dementia of the Alzheimer type. A double-blind, placebo-controlled clinical study on the effect of a standardized ginseng extract on psychomotor performance in healthy volunteers.
Among the psychiatric illnesses associated with old age primary degenerative dementia of the Alzheimer type (DAT) has gained increasing importance in recent years. Even though a curative treatment of the disease is currently impossible, various drugs can be used to slow down its progression. In the present study the influence of oral treatment with 240 mg/day of Ginkgo bilabo special extract EGb 761 (Tebonin forte, manufactured by Dr Willmar Schwabe, Karlsruhe) on the clinical course of DAT was investigated in a double-blind, randomized, placebo-controlled parallel-group design in 20 outpatients. The duration of treatment was 3 months. The primary outcome variable was the sum score in the SKT-test for the determination of attention and memory. Other psychometric tests (trailmaking test, ADAS, CGI) and electrophysiological investigations (EEG topography) were evaluated descriptively. Although the active-treatment group, with a mean sum score of 19.67 points in the, S.K.T., had a poorer baseline level than the placebo group (18.11 points), it experienced an improvement to 16.78 points under treatment with EGb 761 whereas the placebo group deteriorated to 18.89 points. The differences between the baseline and final values formed the basis for a statistical group comparison, which gave a result favourable to EGb 761, at a significance level of p < .013. In addition to this psychometric confirmation of efficacy, certain descriptive trends were found at the psychopathological (Clinical Global Impression) and dynamic functional (EEG findings) levels, which can be interpreted as evidence of effectiveness of Ginkgo biloba special extract EGb 761 in mild to moderate dementia and of local effects in the central nervous system. Inter-group differences in the ADAS cognitive and non-cognitive subscales did not reach statistical significance, probably because of the small sample size. Various tests of psychomotor performance were carried out in a group of 16 healthy male volunteers given a standardized preparation of Korean ginseng (G 115; 100 mg twice a day for 12 weeks) and in a similar group given identical placebo capsules under double-blind conditions. A favourable effect of G 115 relative to baseline performance was observed in attention (cancellation test), processing (mental arithmetic, logical deduction), integrated sensory-motor function (choice reaction time) and auditory reaction time. However, end performance of the G 115 group was superior statistically to the placebo group only in mental arithmetic. No difference between G 115 and placebo was found in tests of pure motor function (tapping test), recognition (digit symbol substitution) and visual reaction time. No adverse effects were reported. It is concluded that G 115 may be superior to placebo in improving certain psychomotor functions in healthy subjects.
Currently, there is a lack of convincing evidence to show a cognitive enhancing effect of Panax ginseng in healthy participants and no high quality evidence about its efficacy in patients with dementia. Randomized, double-blind, placebo-controlled, parallel group trials with large sample sizes are needed to further investigate the effect of ginseng on cognition in different populations, including dementia patients.