Is Ginkgo Biloba Comparable to Donepezil for Treating AD?
Abstract & Commentary
By Norman Relkin, MD, Associate Professor, Clinical Neurology and Neuroscience, NewYork-Presbyterian Hospital, Cornell Campus. Dr. Relkin is on the speaker's bureau for Pfizer, Eisai, and Athena Diagnostics, and does research for Pfizer and Merck.
Synopsis: In this study, ginkgo biloba was just as effective as donepezil in treating Alzheimer's disease.
Source: Mazza M, et al. Gingko Biloba and Donepezil: A Comparison in the Treatment of Alzheimer's Dementia in a Randomized Placebo-Controlled Double-Blind Study. Eur J Neurol. 2006;13:981-985.
Ginkgo biloba has been used by practitioners of Eastern medicine for centuries to boost memory and other health purposes. Although it is not approved in the United States to treat memory loss, it is available over-the-counter, and often advertised as a memory-enhancing agent. Several past placebo-controlled trials failed to demonstrate consistent benefit when Gingko was used to treat memory loss in the elderly or in patients with dementia due to Alzheimer's disease (AD). However, few studies have compared Ginkgo directly to the medications currently approved for treating dementia.
Mazza and colleagues carried out a randomized, controlled, clinical trial of Gingko extract EGB-761 (160 mg/day) vs donepezil (5 mg/day) and placebo in 76 patients with mild-to-moderate AD. The average age of study participants was 68.5 years, their mean MMSE was 18.7, and roughly equal numbers of males and females participated. The study, which was conducted in Italy, used the Kurz test as its primary cognitive outcome measure and the Mini-mental state examination and a clinician-based global assessment as additional metrics. A 4-week placebo run-in period was performed to eliminate placebo responders.
Approximately 80% of subjects completed the 24-week study. No major side effects were observed in the Gingko-treated arm. Patients receiving Gingko improved to an equal degree as those given donepezil on the Kurz et al's global assessments. Improvements were statistically significant, relative to placebo and indistinguishable from donepezil. Gingko recipients scored an average of 0.6 MMSE points higher than their baseline after 24 weeks, vs an increase of 1.2 points for the donepezil group and a decline of 0.25 points for those getting placebo. Mazza et al concluded that Gingko biloba special extract EGb-761 may be as effective as a cholinesterase inhibitor in treating mild-moderate stages of AD.
Commentary
EGB-761 is a special extract of Gingko biloba that is purported to have neuroprotective properties. Past clinical trials have hinted at EGb-761's efficacy in the treatment of dementia, but results have been inconsistent. With only 60 persons completing 24 weeks of treatment and only a single time point at which outcome was measured, this new study adds to only marginally to past claims of Gingko's clinical efficacy and does not establish its comparability to cholinesterase inhibitors. Although no difference was found between Gingko and donepezil on the primary outcome measure, the dose of donepezil employed (5 mg) was half of that usually recommended, and the group sizes were inadequate to document a significant difference, given the small effect size. As in past studies, Gingko was very well tolerated and, if larger controlled studies were to demonstrate comparable benefits, Gingko biloba EGb-761 may someday be accepted as a cost effective alternative treatment for AD.
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