Ginko biloba is a natural product used by many to treat depression, memory problems and other disorders, although scientific documentation of effectiveness is limited. Now two German researchers, Leistner and Drewke, have identified a compound called ginkgotoxin in Ginko that can provoke seizures in laboratory animals and probably in people. Their review is published in the Journal of Natural Products (2010, volume 73, page 33). Ginkgotoxin interferes with vitamin B6, which the body needs to synthesize GABA, the brain's main inhibitory neurotransmitter. In laboratory models, the effect of Ginkgotoxin to produce seizures can be counteracted by also giving vitamin B6.

Ginko also may cause the liver to metabolize antiepileptic drugs faster, thereby lowering blood levels below protective thresholds. People with epilepsy should be aware of the risk for Ginko to cause seizures. Just because a drug is “natural” does not mean that it is free from risk.