Direct‐acting oral anticoagulants: a bridge to nowhere

To the Editor: Patients may require long term anticoagulation for reasons that commonly include deep vein thrombosis, pulmonary embolism or atrial fibrillation.1 In these circumstances, heparin is commonly used for bridging and is discontinued after the effects of warfarin result in a therapeutic international normalisation ratio. It takes approximately 5 days for this to occur because warfarin inhibits the production of vitamin K‐dependent clotting factors II, VII, IX and X.2 The time to therapeutic anticoagulation is a reflection of the half‐lives of the circulating clotting factors and the time for them to diminish from the plasma. This has been our mindset for decades from the perspective of warfarin use.