This study shows that P-gp has little effect on the disposition and oral bioavailability of VRL. A substantial fraction of an oral dose of VRL is absorbed from the gut of wild-type mice. Consequently, first-pass metabolism is the most important factor for explaining the modest oral bioavailability, but the results with RTV suggest that cyp3a plays only a modest role in metabolic breakdown in mice. Apparently, other routes of metabolic elimination are more important. These results suggest that also in patients the oral bioavailability may not gain substantially from the co-administration of a potent P-gp and/or Cyp3a inhibitor.