Warfarin-Drug Interactions Among Older Adults

Andrew Liu, BSc Hon, BScPhm, RPh; Carmine Stumpo, BScPhm, PharmD, RPh


Geriatrics and Aging. 2007;10(10):643-646. 

In This Article

Abstract and Introduction

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.

There is good evidence supporting the use of warfarin for a variety of indications, including the prevention of stroke in patients with atrial fibrillation.[1,2] Despite this compelling evidence, warfarin is underutilized, especially among older adults.[3] A commonly cited explanation for the underuse of warfarin is the increased risk of bleeding.[4,5] Risk factors for bleeding include anticoagulation intensity, increasing age, and drug interactions ( Table 1 ). This article will review the significance and etiology of various drug interactions on the efficacy and safety of warfarin therapy, including practical recommendations to address these interactions, with a focus on older adults.


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