Protease inhibitors Garlic

Compared to baseline saquinavir pharmacokinetic parameters obtained in period 1, the use of garlic reduced the mean saquinavir area under the concentration-time curve (AUC) by 51%, and the maximum (Cmax) and minimum (Cmin) saquinavir concentrations by 54% and 49%, respectively. After a 10-day washout, the AUC, Cmax, and Cmin values were within a range of 60% to 70% of baseline values. The magnitude of the decline in concentration might result in therapeutic failure and viral rebound in patients with HIV. Based on the pharmacokinetic parameters obtained in period 3, it also appears that garlic might have a prolonged, albeit lesser, effect on saquinavir exposure. The effects of combined treatment with other protease inhibitors that are also potent cytochrome P-450 (CYP) enzymes modulators need to be further evaluated. 

Because of reported antiplatelet effects, patients using anticlotting medications (eg, warfarin, aspirin, ibuprofen) should use garlic cautiously. Additional monitoring of blood pressure and signs and symptoms of bleeding is warranted. Garlic may reduce the bioavailability of saquinavir, an antiviral protease inhibitor, but it does not appear to affect the bioavailability of ritonavir. 

Although information is limited, a reduction in saquinavir plasma levels of the magnitude seen in the first study could diminish its antiviral efficacy. All garlic supplements should probably be avoided in those taking saquinavir as the sole protease inhibitor (no longer generally recommended). While the pharmacokinetic effect on single-dose ritonavir was not clinically important, this requires confirmation in a multiple-dose study. 

Two cases of gastrointestinal toxicity were reported in patients taking garlic and the protease inhibitor, ritonavir (Laroche et al. 1999). 

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