Garlic Supplements Can Lower Potency of HIV Drug

A new study conducted by the National Institutes of Health has found that garlic supplements can cut blood concentrations of the antiretroviral drug saquinavir by more than half.

"The clear implication is that doctors and patients should be cautious about using garlic supplements during HIV therapy," study co-author Dr. Judith Falloon, of the National Institute of Allergy and Infectious Diseases (NIAID), said in a statement. The findings were published this week in the online edition of the journal Clinical Infectious Diseases (2001:34). NIAIDNEWS includes a summary of the research.

Falloon said her study was prompted in part by previous research that uncovered a dangerous interaction between the popular herbal remedy St. John's Wort and the protease inhibitor indinavir. "We set out to learn more about these alternative medicine products because there simply are not a lot of clinical data available on them."

In the current study, Falloon and her colleagues tracked blood levels of saquinavir, also a protease inhibitor, in 10 healthy HIV-positive patients. Patients took the drug for 39 days. For part of that time, they also took a standard dose of garlic caplets twice a day. "In the presence of garlic supplements, blood concentrations of saquinavir decreased by about 50 percent," Falloon said. They found that even after a "washout" period of ten days after the patients stopped taking the garlic, blood levels of saquinavir remained 35 percent below normal.

The researchers stressed that more research needs to be done to determine the effect of garlic supplements on combination drug therapies. For now, Falloon said, "it's clear from this study that any patient using saquinavir as the sole protease inhibitor should avoid using garlic supplements."

The researchers indicated that they were not surprised by their findings since garlic and protease inhibitors share the same metabolic route in the body. The exact mechanism by which garlic impedes saquinavir remains unclear.

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