A recent study shows that garlic supplements decrease saquinavir (Fortovase) levels by an average of 51% and are therefore likely to greatly reduce saquinavir's anti-HIV activity. This can lead to the rapid development of resistance to saquinavir. What effect this might have when saquinavir is used with small doses of ritonavir is unknown.

Many people use garlic supplements to reduce cholesterol levels or naturally manage yeast infections, and this is the second study to show that herbal or natural therapies can significantly reduce the levels of the anti-HIV drugs. A previous study showed that St. John's Wort significantly reduced indinavir (Crixivan) levels.

Garlic supplements are likely to significantly reduce levels of the other protease inhibitors as well as the non-nucleoside reverse transcriptase inhibitors. As this study illustrates, there's a definite potential for some herbal and nutritional supplements to lower the effectiveness of anti-HIV therapies or other medications. People who use these herbal or natural therapies should always discuss possible interactions with their doctors and pharmacists.

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