Ginkgo biloba is an herbal remedy that has been utilized for thousands of years in China and elsewhere. It is obtained from the leaves and seeds of a plant that is commonly known as the maiden hair tree, believed to be the oldest living species of tree.
Ginkgo preparations have been used to treat such conditions as asthma, inflammation, dizziness, memory problems, and circulatory problems throughout the brain and body. As of 2002, research has been concentrating on the possibility that Ginkgo biloba may be a helpful adjunct therapy for memory deficits occurring in Alzheimer's disease . Ginkgo is also being explored as a possible treatment for impotence and other circulatory disorders.
Recent research into how Ginkgo biloba affects memory suggests that Ginkgo improves blood flow to the brain by preventing blockages in small blood vessels. These blockages can occur when platelets (blood components that aid in clotting) clump together. Ginkgo seems to decrease platelet stickiness, thus preventing clumping.
The active ingredients of Ginkgo biloba appear to include flavone glycosides and terpene lactones. Flavone glycosides have antioxidant properties. They prevent damage to the cells in the brain by chemicals called free radicals. Terpene lactones improve memory by improving the uptake of the neurotransmitter component choline in the nerve synapses. Terpene lactones also help guard against blood clots within the brain, and may provide some protection against metabolic injury. Improved bloodflow throughout the brain seems to help preserve/improve memory.
Ginkgo biloba is available in a variety of forms, including extracts, capsules, and tinctures.
As with other herbal supplements, standardization issues sometimes make it difficult to verify the actual dose being administered. In general, efficacious preparations appear to contain at least 24% gingko flavone glycosides and 6% terpene lactones. This is the standardized extract that is commonly used in research about this remedy.
Adults may take between 120 and 240 mg of Ginkgo biloba daily, divided into two or three doses.
Because of Ginkgo's effects on platelets, there has been some concern regarding interactions between Ginkgo biloba and anticoagulant medicines, such as warfarin (Coumadin) and aspirin. Studies so far have indicated that Ginkgo does decrease platelet function occasionally. For patients taking Ginkgo, their physician can monitor their platelet function. Rare case reports exist of patients experiencing hemmorhage (including cerebral) while taking Ginkgo.
Most reports on Ginkgo biloba suggest that side effects are relatively rare. However, some people may experience stomach upset, including nausea and/or diarrhea. Others who have taken Ginkgo biloba report headache, dizziness, and weakness.
Ginkgo biloba may interact with more medications than are listed below. People should notify their health care team of all medications and herbals they take.
To avoid the possibility of increased bleeding, Ginkgo biloba preparations should not be used by patients who are also taking blood thinners (anticoagulants), such as aspirin, warfarin (Coumadin), clopidogrel, dipyridamole, heparin, or ticlopidine.
Ginkgo preparations may interfere with the efficacy of anticonvulsants, such as carbamazepine and valproic acid .
Caution should be used when taking Ginkgo with thiazide diuretics or with the antidepressant, trazodone .
Blumenthal, Mark, and others, eds. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Austin: American Botanical Council, 1998.
Zink, Therese and Jody Chaffin. "Herbal 'Health' Products: What Family Physicians Need to Know." American Family Physician October 1, 1998.
Rosalyn Carson-DeWitt, M.D.