Warfarin and acetaminophen interaction in a 47-year-old woman

Leong and Wu describe an adverse drug-drug interaction between acetaminophen and warfarin resulting in a potentially lifethreatening bleed in a patient who needed anticoagulation because of a mechanical valve. Warfarin is a medication that requires careful monitoring and titration, as its effects are subject to individual genetic factors, physiologic and age-related changes, and pharmacodynamic and pharmacokinetic interactions with food and drugs. Even though acetaminophen can interact with warfarin, these 2 medications are commonly coprescribed. It is generally recommended that patients taking warfarin avoid nonsteroidal anti-inflammatory drugs owing to increased bleeding risk, leaving acetaminophen as the only analgesic or antipyretic option.