Low-dose warfarin prevents recurrent thromboembolism

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Low-dose warfarin prevents recurrent thromboembolism

J Fam Pract. 2003 August;52(8):587-604

By

Mary-Beth Fennell Plum, PharmD

BACKGROUND: Prolonging the duration of full-intensity oral anticoagulation can decrease the recurrence of venous thromboembolism, but it often increases the rate of major bleeding above an acceptable risk-benefit ratio. This trial evaluated the efficacy and safety of long-term, low-intensity warfarin for the prevention of recurrent venous thromboembolism.
POPULATION STUDIED: This multicenter study included patients older than 30 years, with documented idiopathic venous thromboembolism who completed at least 3 months of uninterrupted full-dose warfarin therapy (target INR, 2.0–3.0). The median age was 53 years; 47% were female, approximately 87% were white, and 9% were African American. More than 37% had at least 2 previous venous thrombo-embolisms, over 25% had either factor V Leiden or a prothrombin mutation, and all patients were treated with full-dose warfarin for an average of 6 months before enrollment.
STUDY DESIGN AND VALIDITY: This randomized, double-blind, placebo-controlled trial was conducted from July 1998 to December 2002. All patients were involved in a 28-day runin phase to ensure that they could have their warfarin titrated to an INR of 1.5 to 2.0 without exceeding a daily dose of 10 mg. This run-in phase also identified and excluded patients with <85% adherence to the treatment regimen.
OUTCOMES MEASURED: The primary endpoint measured was recurrent venous thromboembolism. A composite endpoint was major hemorrhage (bleeding that required hospitalization or transfusion), recurrent venous thromboembolism, and death from any cause. New stroke events were also monitored.
RESULTS: Due to early termination, the mean duration of follow-up was 2.1 years and the median INR in the warfarin group was 1.7, compared with 1.0 for placebo. Low-intensity warfarin reduced the risk of recurrent venous thromboembolism by 64% (hazard ratio [HR]=0.36; 95% confidence interval [CI], 0.19–0.67; P<.001; number needed to treat [NNT]=22). Warfarin reduced the composite endpoint by 48% (HR=0.52; 95% CI, 0.31–0.87; P=.01; NNT=26).

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Low-dose warfarin prevents recurrent thromboembolism

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