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Are there any interactions with garlic?

Garlic, the bulb of a tall, flowering plant, is used in cooking throughout the world. Some people believe that eating garlic can reduce cholesterol and lower blood pressure. Some claim garlic can cure bacterial, fungal, and viral infections. And some people believe that garlic can prevent aging and cancer. Medical research on garlic—most of which focuses on its ability to reduce cholesterol and blood pressure—is inconclusive.

Garlic may increase the possibility of bleeding in people who are taking anticoagulants or “blood thinners” such as >warfarin (brand name Coumadin), >clopidogrel (Plavix), or >aspirin. Please check with your doctor before starting garlic if you are currently using a blood thinner.

Large doses of garlic can reduce levels of the protease inhibitor saquinavir (>Fortovase, >Invirase). It may also affect other HIV medications such as Crixivan, Norvir, Rescriptor, and Viramune. If you are taking any HIV medications you should not take garlic supplements. Currently, there is no proof that garlic is helpful in HIV infections and garlic supplements may decrease the effectiveness of your HIV therapy.

Sources:
Foster, S., V.E. Tyler. Tyler’s Honest Herbal: A Sensible Guide to the Use of Herbs and Related Products. The Haworth Press, 1999.
Peirce, A. The American Pharmaceutical Association Practical Guide to Natural Medicines. William Morrow & Co., 1999.
The Natural Medicines Comprehensive Database. Pharmacists Letter Inc., 2001.
Pharmacist’s Letter. “Supplements” 17 (3) Pharmacists Letter Inc., 2001.

This answer prepared 4/25/01.