Biological Based Systems
Ginkgo biloba (also known as Maidenhair-tree)
Main Constituents Flavonoids, Biflavonoids, Proanthocyanidins, Trilactonic diterpenes: ginkgolides
Possible Applications
Ginkgo may help improve circulation to the extremities and the brain. In addition, the PDR for Herbal Medicines list the indications for use as symptomatic relief from organic brain dysfunction, intermittent claudication, vertigo and tinnitis. Of note, a recent randomized study evaluating the use for tinnitis was negative. There was no significant symptom difference between the individuals receiving the herb and the individuals receiving the placebo.
A large multicenter study, coordinated by a group in Pittsburgh, is currently underway evaluating the application to improve concentration and memory deficits.
Adverse Reactions and Drug Interactions
While this herb is generally well tolerated, mild gastric complaints have been reported along with blood pressure problems, allergic reactions, headaches, heart palpitations and phlebitis. Hypersensitivity reactions have been documented with spasms, cramps and in some cases, acute toxicity, atonia and adynamia (listed in the Herbal PDR).
Ginkgo biloba interferes with platelet aggregation. Several case reports are available documenting spontaneous bilateral subdural hematomas, subarachnoid hemorrhage and an increase in bleeding time associated with long-term use of the herb.
Concerns for drug interaction involve anticoagulant, antiplatelet and aspirin-containing medications such as warfarin, ticlopidine, enoxaparin, low weight heparins, dipyridamole and clopidogrel, various pain relieving combinations containing aspirin and aspirin with antacid combinations. Ginkgo contains certain chemicals that may also enhance the action of MAO inhibitor drugs; however, a recent study found no additional problem when ginkgo was administered with a MAO inhibitor.
Precautions must also be taken when ginkgo is added to herb/dietary supplement combinations containing other agents that decrease platelet aggregation.
Contraindications
Because no human research data is available for safety and efficacy during pregnancy and lactation, the herb is not recommended. It is also not recommended for individuals at risk for or with a history of intracranial bleeding. Risk factors for intracranial bleeding include systemic arterial hypertension, diabetes, and amyloid senile plaques.
Individuals with any prior hypersensitivity to ginkgo biloba should avoid the herb.
Rob McCaleb's Encyclopedia of Popular Herbs states that the effect of ginkgo is not immediate and the results of most clinical trials showed that doses need to be taken for 4-24 weeks before a treatment benefit was seen.
Scientific Rationale
Ginkgo is a potent inhibitor of platelet-activating factor (PAF) and it functions as an antioxidant. These two features seem to account for most of the health benefit achieved though ginkgo. Too much PAF has been linked to conditions such as allergies, inflammatory disorders and cardiovascular diseases. Ginkgo helps to keep the blood flowing smoothly and has an indirect effect on relaxing the vessels.
Its proposed antioxidant effect helps to prevent oxidative cell damage in the body. The proposed mechanisms are free-radical scavenging and prevention of lipid peroxidation. Lipid peroxidation has been implicated in tissue and vascular damage and neuronal loss. These conditions may contribute to dementia; hence the possible treatment benefit of ginkgo.
According to the PDR for Herbal Medicine, the herb also reduces neutrophil infiltration and increases blood flow to prevent dementia ischemia. In addition, the same text points out the very beneficial membrane stabilizing activity of gingko biloba.
References
1. Physician's Desk Reference on Herbal Medicine. Montvale, NJ: Medical Economics Company; 2000.
2. Blumenthal M et al. Commission E Monographs. Austin, TX: American Botanical Council; 1998.
3. Website http://www.onemedicine.com.
4. DeBusk RM, Treadwell, PR. Herbs as Medicine: What you should know. Tallahassee, FL: DeBusk Communications; 2000.
5. Complementary and Alternative Cancer Methods. Atlanta, GA: American Cancer Society; 2000.
6. McCaleb RS, Leigh E, Morien K. The Encyclopedia of Popular Herbs. Roseville, CA: Prima Health Publishing; 2000. |
