Common Medications with Possible Interactions with Warfarin Warfarin is subject to the effects of drug interactions because it has a narrow therapeutic range and complex pharmacokinetics and pharmacodynamics. Other agents that alter the protein binding, or more commonly, the hepatic metabolism of warfarin can yield dramatic changes in patients’ INR values. Whether these interacting agents are given continuously, for a defined period, or cyclically can dramatically change the therapeutic plan. Agents that interact with the CYP2C9 enzyme are more likely to have a dramatic response because the more potent S-isomer is metabolized by this pathway. #Pharmacology #Warfarin #Medications #Interactions #INR #Increases #Decreases #Drug