In a 2005 study published in the "British Journal of Haematology," researchers noted the importance of physicians receiving a full drug history, including complementary medicines, when treating patients with the anticoagulant medicine warfarin in order to regulate anticoagulation. Gingko biloba, often used as a complementary medical treatment, has not been shown to affect warfarin when taken at recommended doses, but high doses may increase the risk of bleeding.
Warfarin is an anticoagulant medication that works to decrease the clotting ability in the blood. It is most often prescribed to patients with a history of heart attack or stroke, mechanical heart valve recipients, irregular heartbeats, venous thrombosis and pulmonary embolisms. It comes in a tablet form and, according to the National Institutes of Health, is usually taken once a day. Because warfarin affects how your blood clots, it is important to have regular testing of your blood to make sure the medication is thinning the blood enough without increasing your risk of bruising or bleeding.
Gingko biloba, according to the University of Maryland Medical Center, is the oldest living tree species and the best-selling herbal supplement in the United States and Europe. It is used in traditional medicine to treat circulatory disorders and enhance memory. Flavonoids and terpenoids are the two main chemicals found in gingko and they are believed to have antioxidant properties. The standard dosage for memory impairment and cardiovascular function is 120mg a day divided into two doses but can go as high as 240mg. Results from gingko biloba can take up to four to six weeks.
Researchers have looked at the possible interactions between warfarin and gingko biloba. A 2005 study published in the "British Journal of Clinical Pharmacology" looked at the use of gingko and ginger in 12 healthy male subjects who received a single 25mg dose of warfarin alone or after a full week of taking the recommended doses of ginger and gingko therapy. Their results determined that, at the recommended doses, neither ginger nor gingko biloba affected the clotting status in healthy subjects.
While gingko biloba does not appear to affect warfarin treatments, you should discuss its use with your physician so he is aware of the possible interactions. If you are taking more than the standard recommended dose of gingko, it may affect your bleeding times, and your physician may need to adjust your warfarin dosage. Make sure your physician is aware of all medications, whether prescription or over-the counter supplements, so he can best adjust your warfarin levels.
- "British Journal of Haematology"; Complementary and Alternative Medicine Use Among Patients Starting Warfarin; NA Ramsay et al.; September 2005
- National Center for Complementary and Alternative Medicine; The Use of Complementary and Alternative Medicine in the United States; December 2008
- MedlinePlus; Warfarin; September 1, 2008
- University of Maryland Medical Center; Gingko Biloba; March 26, 2009
- "British Journal of Clinical Pharmacology"; Effect of Gingko and Ginger on the Pharmacokinetics and Pharmacodynamics of Warfarin in Healthy Subjects; X. Jiang et al.; April 2005