Ginkgo (ginkgo biloba) is a tree which originated in Asia but is now found growing in many American cities. The medicinal use of ginkgo has been the subject of more research than most other herbal agents. A few controlled clinical trials have suggested some improvement in symptoms of dementia (especially Alzheimer's disease), but the reported effect is not large. There may also be some benefit to other people seeking improved memory and thinking ability, but there is less evidence for this effect. Most reports have suggested that the herb must be used for several weeks before a benefit can be noticed. Nevertheless, ginkgo is widely used, usually in the form of ginkgo extract.

Any improvement in cognitive function is often credited to an increase in circulation. Some studies have found ginkgo to be beneficial in treating circulatory disorders but it should not be used by people taking anticoagulants such as warfarin (Coumadin) because of possible bleeding problems. Similar interactions with aspirin and other nonprescription pain relievers are also possible. Studies are underway to see whether taking ginkgo affects the way the body uses other medications, perhaps including some seizure medicines.

Seizures have been reported in a few people taking ginkgo, but the number of these reports has been very small considering the large numbers of people who have used it. Many of the people involved were also taking other substances and there is not enough information to definitely blame any particular form or dosage of ginkgo for the seizures. Bilobalide is a substance found in ginkgo that has antiseizure effects in animals, but we know less about the effects of total ginkgo extract, the form usually taken.

Read more about ginkgo in the "About Herbs" section of the Memorial Sloan-Kettering Cancer Center website. (If you have not visited the site before, the information on ginkgo will be preceded by a Disclaimer.)

Much of the information in this article is based on Spinella M: Herbal medicines and epilepsy: The potential for benefit and adverse effects. Epilepsy Behav 2001; 2(6):524-532. (PMID 12609386)

Topic Editor: Steven C. Schachter, M.D.
Last Reviewed:12/15/06