Workshop: Warfarin drug interactions: Detection, prediction, prevention

Abstract

Oral anticoagulant therapy is frequently complicated by the interaction of warfarin with numerous drug compounds. While concurrent use of warfarin and interacting drugs is not an absolute contraindication, clinicians must employ various strategies to detect possible drug interactions, predict patient response, and prevent adverse clinical outcomes. Thorough ongoing patient education plays a significant role in the prevention of unreported medication use. Patient interviewing techniques must include an assessment of nonprescription drug use as well as drugs taken by prescription. Recent developments in the characterization of the stereoselective, regioselective oxidative metabolism of warfarin may help to explain the unpredictable nature of warfarin drug interactions with respect to patient susceptibility, magnitude of response, time of onset, and duration of effect. When an interacting drug is initiated, discontinued, or used intermittently, adverse clinical outcomes can be avoided by diligent monitoring of prothrombin time, routine physical assessment of patient response, and appropriate warfarin dosage alterations.