Ginkgo biloba extract for age-related macular degeneration

Abstract

Ginkgo is used in the treatment of peripheral vascular disease and 'cerebral insufficiency'. It is thought to have several potential mechanisms of action including increased blood flow, platelet activating factor antagonism, and prevention of membrane damage caused by free radicals. Vascular factors and oxidative damage are thought to be two potential mechanisms in the pathology of age-related macular degeneration (AMD). The objective of this review was to determine the effect of Ginkgo biloba extract on the progression of AMD. We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 10), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to October 2012), EMBASE (January 1980 to October 2012), Allied and Complementary Medicine Database (AMED) (January 1985 to October 2012), OpenGrey (System for Information on Grey Literature in Europe) (www.opengrey.eu/), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 5 October 2012. We searched the reference lists of identified reports and the Science Citation Index. We also contacted investigators of included studies for additional information. All randomised trials in people with AMD where Ginkgo biloba extract had been compared to control were included. The review author extracted data using a standardised form. The data were verified with the trial investigators. Trial quality was assessed. Two published trials were identified that randomised a total of 119 people. In one study conducted in France, 20 people were randomly allocated to Gingko biloba extract EGb 761 80 mg twice daily or placebo. In the other study conducted in Germany, 99 people were randomly allocated to two different doses of Ginkgo biloba extract EGb 761 (240 mg per day and 60 mg per day). Treatment duration in both studies was six months. Both trials reported some positive effects of Ginkgo biloba on vision however their results could not be pooled. Adverse effects and quality of life for people with AMD were not reported. The question as to whether people with AMD should take Ginkgo biloba extract to prevent progression of the disease has not been answered by research to date. Two small trials have suggested possible benefit of Gingko biloba on vision and further trials are warranted. Ginkgo biloba is widely used in China, Germany, and France. Future trials should be larger, and last longer, in order to provide a more robust measure of the effect of Gingko biloba extract on AMD.