Effect of short-term administration of garlic supplements on single-dose ritonavir pharmacokinetics in healthy volunteers

AIMS: To evaluate the effect of acute dosing of garlic supplements on the single‐dose pharmacokinetics of ritonavir. METHODS: Ten healthy volunteers (five male, five female) were equally randomized in a crossover design to receive 400 mg of a single dose of ritonavir within 10 min after eating breakfast either alone or with 10 mg of Natural Source Odourless Garlic. They received a total of eight doses of garlic extract (2 x 5 mg capsules) taken twice daily for 4 days. Ritonavir and the seventh garlic dose were administered simultaneously. RESULTS: Coadministration of garlic nonsignificantly decreased area under the plasma concentration‐time curve (AUC(0, infinity )) by ‐17% (90% confidence interval (CI), ‐31% to 0%; range ‐46% to 68%) and peak plasma concentration of ritonavir by ‐1% (90% CI, ‐25% to 31%; range ‐51% to 136%). CONCLUSIONS: Acute dosing of the garlic capsules over 4 days did not significantly alter the single‐dose pharmacokinetics of ritonavir in healthy volunteers. Given the complex effects of both ritonavir and garlic on drug metabolism, the results of our study should not be extrapolated to steady‐state conditions, where the possibility of an interaction still needs to be evaluated.