Temporary reversal of anticoagulation using oral vitamin K

Brief reversal of oral anticoagulant therapy is frequently necessary prior to minor surgery or invasive procedures. We sought to determine the effect of an oral dose of 2.0 mg of vitamin K-1 on the international normalized ra tio (INR) among patients with a stable therapeutic INR who were maintained on their daily dose of warfarin. We prospectively studied a convenience coh ort of patients attending an anticoagulation clinic who had either just com pleted treatment for venous thromboembolism or were receiving prophylaxis f or atrial fibrillation, cardiomyopathy, or peripheral vascular disease. Eac h patient received an oral dose of 2.0 mg of aqueous vitamin K-1. Serial IN R measurements were taken over 1 week. There was wide variation in the INR response between patients, from no change to complete reversal of anticoagu lation. The effect also varied widely over time. There was a significant in verse correlation between the fall in logarithm of the INR and the daily wa rfarin dose required to achieve an INR value of 2.5 (r = -0.52, p = 0.011). Use of a 2.0 mg oral dose of vitamin K-1 does not reliably reverse (correc t) a therapeutic INR in patients maintained on their daily dose of warfarin .