Impact of Aspirin on Warfarin Control as Measured by Time in Therapeutic Range

Abstract

Warfarin is an oral anticoagulant widely prescribed for a variety of thromboembolic indications including venous thromboembolism (VTE), deep vein thrombosis (DVT) and the prevention of stroke associated for atrial fibrillation (AF) 1. Warfarin requires ongoing monitoring of Internationalised Normalised Ratio (INR) due to a narrow therapeutic index and interactions with numerous drugs 2. The time in therapeutic range (TTR) is often used to indicate the quality of warfarin therapy due to the established correlation between higher mean TTR and reduced complications such as bleeding and thromboembolism 3. TTR is strongly associated with bleed risk, but increased bleeding with warfarin has also been associated with patient comorbidities and concurrent administration of other medication linked to bleeding including antiplatelet agents and non‐steroidal anti‐inflammatories (NSAIDs) 4.