Garlic supplements reduce the serum level of the protease inhibitor saquinavir considerably, concludes a report from the National Institute of Allergy and Infectious Diseases. Investigators suspected negative interactions because protease inhibitors share the CYP450 metabolic pathway with garlic (Clin Infect Dis. 2002;34:234-238).
The researchers assessed baseline serum levels in 10 HIV-negative volunteers, who took 1200 mg of saquinavir three times daily. Then, the volunteers added garlic caplets to their daily regimen. The team reassessed the volunteers at the end of the garlic-taking phase and 2 weeks later, after a garlic washout period. While the volunteers were taking garlic, their average saquinavir serum levels dropped by 50%. After the washout, serum levels were still 35% lower than baseline.
Vastag B. Garlic and HIV Medication. JAMA. 2002;287(3):308. doi:10.1001/jama.287.3.308-JHA10014-2-1