Garlic Supplements Can Alter Blood Concentration of Protease Inhibitor Saquinavir

Garlic supplements can interfere with the protease inhibitor saquinavir when the two are taken together, according to a new study appearing in the online edition of Clinical Infectious Diseases. Researchers from the National Institute of Allergy and Infectious Diseases and Tibotec-Virco Laboratory studied nine healthy HIV-negative volunteers. For the first three days of the study, the participants received doses of saquinavir, and researchers evaluated the drug's concentration in their blood. The participants then took garlic caplets twice a day for three weeks. After patients spent three weeks on both saquinavir and garlic, the researchers found that overall blood levels of saquinavir had dropped by an average 51%, while average maximum concentrations dropped 54%. Participants then stopped taking garlic supplements for 10 days, but their blood levels of saquinavir still averaged about 35% lower than they had before taking the supplements. Researchers said they chose to study garlic because it is known as a cholesterol fighter, and increased cholesterol levels are one side effect of HIV medications. In addition, garlic and protease inhibitors both enter the body via a metabolic route known as the CYP450 enzyme system. The study authors are not sure how garlic supplements disrupt the intake of saquanivir or how the supplements would affect a combined antiretroviral regimen. "More research is needed in this area, but it's clear from this study that any patient using saquinavir as the sole protease inhibitor should avoid using garlic supplements," Dr. Judith Falloon, an AIDS clinical researcher at NIAID and a co-author of the study, said (NIH release, 12/5).