Interaction between acetaminophen and warfarin in adults receiving long-term oral anticoagulants: a randomized controlled trial.

Purpose: We investigated whether acetaminophen, given at 2 g/day and 3 g/day might potentiate the anticoagulant effect of warfarin.

Methods: Forty-five patients on stable warfarin therapy, enrolled in this prospective, randomized, parallel (three arms), placebo-controlled study, received a 10-day regimen of acetaminophen (2 g/day or 3 g/day) or placebo.

Results: The mean maximal INR increase was 0.