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

Br J Clin Pharmacol. 2003 Feb;55(2):199-202. doi: 10.1046/j.1365-2125.2003.01736.x.


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.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Oral
  • Analysis of Variance
  • Chromatography, High Pressure Liquid
  • Cross-Over Studies
  • Female
  • Garlic*
  • HIV Protease Inhibitors / pharmacokinetics*
  • Humans
  • Male
  • Plant Extracts / pharmacology
  • Plant Preparations / pharmacology*
  • Ritonavir / pharmacokinetics*


  • HIV Protease Inhibitors
  • Plant Extracts
  • Plant Preparations
  • Ritonavir