When a single 125 mg dose of oral aprepitant was administered on Day 1 and 80 mg/ day on Days 2 and 3 to healthy subjects who were stabilised on chronic warfarin therapy, there was no effect of oral aprepitant on the plasma AUC of R(+) or S(-) warfarin determined on Day 3; however, there was a 34% decrease in S(-) warfarin (a CYP2C9 substrate) trough concentration accompanied by a 14% decrease in INR 5 days after completion of dosing with oral aprepitant.