Ginkgo

Common names: Ginkgo, maidenhair tree, kew tree, ginkyo, yinhsing (silver apricot-Japanese)

Efficacy rating:

ÒÒÒ...Positive clinical trials

Safety rating:

What is Ginkgo?

The ginkgo is the world's oldest living tree species; it can be traced back more than 200 million years to the fossils of the Permian geologic period and is the sole survivor of the family Ginkgoaceae. Individual trees may live as long as 1,000 years and grow to a height of about 125 feet. Ginkgo has characteristic fan-shaped leaves. Male trees more than 20 years old blossom in the spring. Adult female trees produce a plum-like, gray-tan fruit that falls in late autumn. Its fleshy pulp has a foul, offensive odor and causes contact dermatitis. The edible inner seed resembles an almond and is sold in Asian markets.

What is Ginkgo used for?

The ginkgo species almost became extinct during the last ice age that began approximately 2 million years ago. The species survived in China, where it was cultivated as a sacred tree and still is found decorating Buddhist temples throughout Asia. Preparations have been used for medicinal purposes for more than a thousand years. Traditional Chinese physicians used ginkgo leaves to treat asthma and chilblains (inflammation of the small blood vessels in the skin in response to cold, but above freezing, temperatures). Ancient Chinese and Japanese people ate roasted ginkgo seeds and considered them a digestive aid and preventive for drunkenness. In the Western world, ginkgo has been used since the 1960s when technology made it possible to isolate its essential compounds. The flavonoids act as free radical scavengers and the terpenes (ginkgolides) inhibit platelet activating factor. Ginkgo is one of the most commonly prescribed medications in Europe, but is not approved for medical use in the US where it is sold only as a nutritional supplement.

Ginkgo has been studied extensively for its antioxidant and neuroprotective effects, as well as for treatment of cerebral insufficiency, cognitive impairment, dementia, peripheral vascular disease, premenstrual syndrome, schizophrenia, tinnitus, and vertigo. Limited studies also support its use in treating asthma, several forms of cancer, Raynaud disease, hyperlipidemia, radiation exposure, and drug-induced sexual dysfunction.

What is the dosage of Ginkgo?

Standardized ginkgo leaf extracts such as EGb 761 (Tebonin forte, Schwabe) have been used in clinical trials for cognitive and circulatory disorders at daily doses of 120 to 720 mg of extract. Extracts are usually standardized to 24% flavones and 6% terpene lactones. Ginkgo is commercially available in several forms including teas, liquids, colas, capsules, extracts, tablets, sprays, and bars.

Is Ginkgo safe?

Individuals with known hypersensitivity reactions should avoid ginkgo use. Ginkgo may also interact with several medications. Because of the potential risk of increased bleeding or hemorrhage, ginkgo use should be avoided with antiplatelet (eg, aspirin) or anticoagulant (eg, warfarin) agents, or in patients with vitamin K deficiency. Patients with a history of, or a predisposition to, seizures should not take ginkgo.

Ginkgo should not be used during pregnancy and lactation. Animal studies indicate that ginkgo leaf has antiplatelet activity, as well as emmenagogue (stimulating menstrual flow) and hormonal properties.

Ginkgo biloba may increase the risk of bleeding in individuals taking aspirin, ibuprofen, or warfarin and increase the risk of sedation in patients taking trazodone. Ginkgo biloba may elevate plasma concentrations of nifedipine, increasing the therapeutic and adverse effects. Conversely, ginkgo biloba may reduce plasma concentrations of omeprazole and tolbutamide, decreasing the therapeutic effects. Patients receiving these agents should be cautioned against use of ginkgo biloba or other herbal products without consulting their health care provider. Ginkgo biloba administration may increase the effectiveness and decrease extrapyramidal side effects of haloperidol, but only slightly affects the activity of alprazolam.

Severe side effects are rare; possible effects include headache, dizziness, heart palpitations, as well as GI and dermatologic reactions. Ginkgo pollen can be strongly allergenic. Contact with the fleshy fruit pulp causes allergic dermatitis similar to poison ivy.

A toxic syndrome has been recognized in Asian children who have ingested ginkgo seeds.

References

Copyright © 2006 Wolters Kluwer Health

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