Natural Products

Ginkgo

Ginkgo biloba

Efficacy

• Indications with proven efficacy:
  None
• Indications with possible, but poorly documented efficacy - the use of this product cannot be recommended:
  Cerebral vascular insufficiency
  Cognitive function improvement in elderly people with mild to moderate memory impairment
  Early Alzheimer's disease
  Peripheral vascular insufficiency (intermittent claudication, Raynaud's phenomenon)
  Vascular or mixed dementia
• Also used for these other indications, but with no proof of efficacy:
  Acute altitude sickness
  Antidepressant-induced sexual disorder
  Atherosclerosis
  Cognitive function improvement in healthy people
  Depression
  Erectile disorder
  Heart failure
  Male infertility
  Migraine
  Multiple sclerosis
  Premenstrual syndrome
  Retinopathy and macular degeneration
  Tinnitus of vascular origin
  Vertigo of vascular origin

Security

• Risk of Drug Interactions: Moderate
• Adverse Effects: Rare

What is it?

Ginkgo biloba is a very old tree, the last remaining member of the Ginkgoceae family. Ginkgo fossils have been found to be over two hundred million years old and the tree itself can live as long as one thousand years.

A standardized extract from the leaves of the ginkgo tree is used. It usually contains 24% flavonoid glycosides and 6% terpenoids. Flavonoid glycosides contain several compounds such as kaempferol, quercetin, and isorhamnetin and primary terpenoids are ginkgolides A, B, C, M, J, and bilobalide. Ginkgo's medicinal effects result from all these constituents, and cannot be attributed to any one particular component.

Standardized ginkgo extract is thought to positively affect the cognitive functions in two ways: by stimulating populations of nerve cells that are still functional, and by protecting nerve cells from pathologic influences. In addition to its antioxidant properties, ginkgo may also improve capillary fragility and permeability, inhibit platelet-activating factor, increase cerebral blood flow and reduce blood viscosity. It may also have other beneficial properties.

Warning

In 2004, Canada adopted new regulations that control the manufacturing, packaging, labeling and importing of natural health products. The new regulations also include an adverse reaction reporting system. Products that conform to the regulation's criteria are identified with a natural product number (NPN) or homeopathic medicine number (DIN-HM) and can be legally sold in Canada. This number indicates that the product meets specific criteria for safety and purity, not that it is effective for any indication. Medicinal plants content varies naturally from plant to plant – just as fruits from the same package may vary in taste and texture. There is no standard to measure the active content of each plant. Thus, efficacy of natural products should be expected to vary from brand to brand as well as from bottle to bottle of the same brand.

For more information about the Natural Health Products Regulations, or to check if a product has been assessed, visit the Health Canada website at http://www.hc-sc.gc.ca/dhp-mps/prodnatur/index-eng.php.

Does it work?

Ginkgo is mainly used to treat Alzheimer's disease, cerebral and peripheral vascular insufficiency, vascular dementia, and it is also used in other medical conditions, in which it may be of some benefits:

• Alzheimer's disease;
  Cerebral vascular insufficiency;
  Vascular or mixed dementia:
  A typical dose is 120 to 240 mg of standardized leaf extract daily, in 2 to 3 divided doses. Treatment should continue for at least 8 weeks, and therapy should be reviewed after 12 weeks. Ginkgo could slightly enhance cognitive functions but don't stop Alzheimer's disease evolution.
• Peripheral vascular insufficiency:
  Ginkgo has been found effective in the treatment of intermittent claudication and Raynaud's phenomenon. Doses of 120 to 240 mg of standardized leaf extract are administered daily, in 2 to 3 divided doses. Treatment should continue for at least 6 weeks before its efficacy can be evaluated.
• Cognitive function improvement in elderly people with mild to moderate memory impairment:
  Doses from 120 mg to 160 mg standardized leaf extract daily have been used.

Is it safe?

• Ginkgo is not associated with any specific toxicity and is very well-tolerated. A few rare cases of gastro-intestinal upset, headaches, and bleeding have been reported. Allergic skin reactions may occur in some people. To avoid adverse reactions, start at lower doses and titrate to higher doses as needed.
• Since there are no safety data available concerning its use during pregnancy and breast-feeding, pregnant and lactating women should not use ginkgo.
• Ginkgo may enhance the effects of nifedipine (Adalat) as well as antiplatelet agents and oral anticoagulants (Coumadin). Use of Ginkgo with trazodone (Desyrel) has been associated with coma. Before taking ginkgo extracts, check with your pharmacist to make sure that there are no interactions with your regular medication.
• It is recommended that patients stop taking ginkgo at least 36 hours before surgery.

Clinical notes

• Ginkgo is an extremely popular and widely used natural remedy. Many studies have concluded that ginkgo is effective in some indications. In 1995, German physicians have written more than 6 million prescriptions for standardized ginkgo leaf extracts.

References

1. Blumethal M et al. The Complete German Commission E monographs, 1998
2. Natural Medicines Comprehensive Database, Therapeutic Research Faculty, 2007
3. Lininger S. et Al. The Natural Pharmacy, Prima Health, 1998
4. Barnes J. et Al. Herbal Medicines, 2nd edition, Pharmaceutical Press, 2002
5. Pierce Andrea, Practical Guide to Natural Medicines, 1999
6. Passeportsanté.net. Ginkgo biloba. http://www.passeportsante.net
7. Rotblatt M. et Ziment I. Evidence-Based Herbal Medicine, Hanley & Belfus, 2002
8. Taylor J. CE: Phytomedicinals: Uses, precautions, and drug interactions. Drug Topics 2003;1:79
9. Gold P et al. The Lowdown on Ginkgo Biloba. Scientific American, March 9, 2003
10. Sierpina VS et al. Ginkgo Biloba. American Family Physician, September 1, 2003
11. Canadian Adverse Reaction Newsletter, January 2004; 14(1)