A Survey of Oral Vitamin K Use by Anticoagulation Clinics

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Abstract
TWO TO 3 MILLION patients in the United States are receiving long-term anticoagulant therapy with warfarin. Therapy with warfarin carries the benefit of prevention of thrombosis and the risk of hemorrhage. Published reports of annual bleeding risk have reported episodes of major bleeding to be as low as 1.3% per year in large, international trials of warfarin use to prevent stroke in atrial fibrillation.1 In many of these trials, patient selection and use of anticoagulation clinics with strict protocols and highly trained staff probably influenced the outcomes favorably. Much higher rates of major bleeding in patients receiving anticoagulation of 3% to 7% per year have been reported in studies that examined more "real world" examples of clinical care.2,3 These data suggest that there are 26 000 to 210 000 major bleeding episodes related to warfarin use per year in the United States.