May increase anticoagulant effect of warfarin. Absorption may be increased by metoclopramide or domperidone & reduced by cholestyramine. Increased susceptibility to harmful effects to the liver w/ enzyme stimulating medicines. Syr: Alcohol, chloramphenicol, aspirin, phenobarb, liver enzyme inducers, hepatotoxic agents. Supp: Increased risk of toxic effects w/ other painkillers in prolonged use; chronic intake of alcohol. Reduces efficacy w/ oral contraceptive. Increased risk of hypothermia w/ phenothiazines. Increases exposure to chloramphenicol. Probenecid may affect elimination.