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Br J Clin Pharmacol. 2003 Feb;55(2):199-202.

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

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Clinical Investigation Unit, The Ottawa Hospital-General Campus, Health Canada, Ottawa, Ontario, Canada.



To evaluate the effect of acute dosing of garlic supplements on the single-dose pharmacokinetics of ritonavir.


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.


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%).


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.

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