Andrew Liu, BSc Hon, BScPhm, RPh, Clinical Pharmacist, Thrombosis Service, Toronto East General Hospital, Toronto, ON.
Carmine Stumpo, BScPhm, PharmD, RPh, Director, Pharmacy and Emergency Services, Toronto East General Hospital, Toronto, ON.

Warfarin-drug interactions are often encountered in the care of older adults. Interactions may be classified as pharmacokinetic, resulting in changes in serum warfarin concentrations, or pharmacodynamic, resulting in changes in hemostasis or platelet function. Knowledge of these mechanisms of warfarin-drug interactions may help identify warfarin interactions, facilitate prescribing decisions, and assist with appropriate monitoring.
Key words: warfarin, drug interactions, anticoagulants, cytochrome P-450 enzyme system, older adults.