a ginkgo leaf

Ginkgo biloba is one of the most popular botanical medicines in both Europe and America, but Chinese healers take the prize. They have been using this ancient tree for thousands of years to treat asthma and cold injury to fingers and toes, as well as to aid memory.

The roasted seeds were traditionally used in China and Japan for indigestion and intoxication. Getting the seeds to roast required care and knowledge, however, because the fruit smells bad and causes a nasty rash.

Current ginkgo formulations are based on an extract of the leaves picked in the fall, when the concentration of the active ingredients is highest.

Active Ingredients

Ginkgo leaves, like most plant products, contain a complicated mix of compounds. At least forty different flavonoids have been identified, as well as flavonols such as quercitin and kaempferol.

Standardized extracts contain between 22 and 27 percent of such flavonol glycosides. The best-studied of these, an extract produced by a German-French consortium, is standardized to 24 percent flavonol glycosides.

In addition, there are terpene compounds that have been named bilobalide and ginkgolides A, B, C, J, and M, with ginkgolide B perhaps the most active. A standardized extract should contain 6 to 7 percent of these terpene lactones.

One study in the 1980s indicated that the individual components of ginkgo biloba extract (GBE) do not provide the same clinical benefits as the extract itself. Some researchers believe that for many herbs a single ingredient may provide most if not all of the therapeutic benefit. Ginkgo, however, seems to contain several compounds that work together for maximum effect.

EGb 761, an extract used in many of the better clinical studies, is manufactured by Dr. Willmar Schwabe AG of Karlsruhe, Germany. It is sold in the United States under the brand names Ginkoba, Ginkgo-D, and Ginkgold.

Uses of Ginkgo

Ginkgo is the most frequently prescribed botanical medicine in Germany and is popular throughout Europe, both as oral medicine and as injections. It is most often used to treat dementia or memory loss. A study in the United States demonstrated that it is more effective than placebo in slowing the loss of mental ability due to Alzheimer’s disease. This finding is consistent with the results of a review of placebo-controlled studies, which found that GBE produces a modest improvement in memory test scores roughly similar to that associated with the Alzheimer’s disease drug Aricept.

One popular hypothesis to explain this benefit suggests that improved circulation to the brain is important. Another possibility is that ginkgo may help protect brain cells from neurotoxicity.

A minimum of six weeks of treatment is needed to assess whether GBE will prove helpful.

Depression in older people that has not responded to other treatments such as antidepressants or St. John’s wort may be an early symptom of mental decline. In Europe, this resistant depression is treated with ginkgo for at least eight weeks.

Ginkgo is also used to treat intermittent claudication, a condition in which inadequate circulation in the legs causes pain when walking. Combination therapy that includes exercise is most effective for this problem. Other circulatory problems that sometimes respond to GBE are Raynaud’s phenomenon and postphlebitis syndrome. Peripheral blood flow increases by approximately 40 to 45 percent after GBE is administered.

Tinnitus, or ringing in the ears, is sometimes caused by drugs, especially aspirin or other salicylates. In animals, ginkgo reduces the behaviors associated with salicylate-induced tinnitus. Research in people has shown that up to 40 percent of patients with tinnitus attributed to inadequate blood flow to the ear responded to treatment with GBE. They required treatment for two to six months before a response was noted.

Ginkgo may be even more effective for people with vertigo due to inner ear problems.

The traditional Chinese use of ginkgo was to treat asthma, and a double-blind crossover study confirmed that ginkgolides found in GBE can alleviate the inflammation and allergic response that lead to bronchospasm.

Ginkgo has strong antioxidant activity and appears to protect nerves from nitric oxide produced by inflammation. It also helps protect cholesterol in the body from oxidation.

GBE use has been suggested to reduce breast tenderness associated with premenstrual syndrome.

One unusual use of ginkgo has not been studied systematically. Antidepressants like Prozac, Paxil, and Zoloft frequently interfere with a person’s ability to achieve orgasm. Psychiatrist Valerie Raskin has recommended ginkgo to reverse this side effect.

Dose

For treating dementia: 120 to 240 mg daily, divided into two or three doses. For intermittent claudication, tinnitus, or vertigo: 120 to 160 mg daily, in two or three doses. Three brand-name products sold in the United States are essentially the same as German products that have been carefully standardized. They are Ginkoba, Ginkai, and Ginkgold.

Special Precautions

The German information for the prescriber (Commission E Monograph) cautions the health care provider to diagnose the cause of dementia carefully before starting a patient on GBE, so that underlying disease contributing to the confusion and memory loss can be detected and treated.

Pregnant women should be wary of taking any therapeutic herb, including ginkgo, not because we know it to be harmful, but because it has not been proved safe.

Because ginkgo seeds and leaves contain a toxin that can affect nerve cells, people with epilepsy should not take GBE. In theory, it might make anticonvulsant medications less effective.

Anyone considering using ginkgo for a serious condition should check with a physician to avoid harmful interactions with other drugs. Ginkgo interferes with blood platelets coming together to form blood clots. While this action could be beneficial under some circumstances, it could cause problems for a surgical patient.

Be sure to tell the doctor you are taking ginkgo and discontinue the herb a week or two before surgery.

Adverse Effects

Very few side effects have been reported with ginkgo biloba extract except for complications associated with the interactions below.

Digestive upset, such as indigestion or nausea, has been reported. Taking the herb with food often helps relieve this problem. Ginkgo may also precipitate bleeding, especially in susceptible individuals or in combination with anticoagulants.

Rarely, people have experienced headache, dizziness, or rash. The fruit, in particular, is capable of causing contact dermatitis similar to that associated with poison ivy or mango.

Possible Interactions

Ginkgo biloba inhibits platelet-activating factor (PAF) produced by the body. Although this may explain some of its benefits for asthma and circulatory problems, it might also pose a hazard in conjunction with anticoagulants such as Coumadin. In fact, an elderly woman on Coumadin had a hemorrhagic stroke after two months of ginkgo. Ginkgo might also interact with other anti-clotting drugs such as aspirin, Plavix, or Ticlid to increase the risk of bleeding.

Hemorrhage with the combination of ginkgo and aspirin has been reported. We advise against combining arthritis medicines such as ibuprofren (Advil, Motrin IB, etc.) or diclofenac (Cataflam, Voltaren) with prescription blood thinners, and it would also be prudent to avoid adding GBE to any of these medications.

The American Herbal Products Association suggests that ginkgo may interact with MAO inhibitors such as Eldepryl, Nardil, or Parnate.

Because of a concern that ginkgo could possibly make a person more vulnerable to seizures, it probably should not be taken together with other drugs known to increase the risk of seizures.

Antidepressants such as Elavil (amitriptyline), Ludiomil (maprotiline), and Wellbutrin (bupropion) belong in this category, along with the smoking cessation aid Zyban (bupropion).

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