PREVENTion of recurrent venous thromboembolism (2003)


Long-term prevention of recurrent idiopathic VTE

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To test the hypothesis that long-term, low-intensity warfarin therapy is an effective and safe method of reducing the risk of recurrent VTE in patients with a previous episode of idiopathic VTE

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Trial design

Randomized, double-blind, placebo-controlled study with a 28-day openlabel run-in phase
Active treatment: low-intensity warfarin (target INR 1.5–2.0) (n=255)
Control treatment: placebo (n=253)

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Primary efficacy endpoint: composite of recurrent VTE, major hemorrhage, and death from any cause
Secondary endpoints: minor bleeding, stroke (hemorrhagic and thromboembolic)

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Trial participants

508 patients (≥30 years, mean age 53 years) with idiopathic VTE who had completed 3 uninterrupted months of oral anticoagulant treatment with full-dose warfarin

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Efficacy outcome: Low-intensity warfarin was associated with a 48% reduction in the composite end point of recurrent venous thromboembolism, major hemorrhage, or death (4.1 vs. 8.0/100 person-years). Recurrent VTE occurred in 37 of 253 patients assigned to placebo (7.2/100 person-years), as compared with 14 of 255 patients assigned to low-intensity warfarin (2.6/100 person-years); the relative risk reduction was 64%
Safety outcome: Major hemorrhage occurred in 2 patients assigned to placebo (0.4/100 person-years) and 5 assigned to low-intensity warfarin (0.9/100 person-years). A total of 34 patients in the placebo group and 60 patients in the warfarin group reported minor bleeding or bruising. 8 patients given placebo and 4 patients given low-intensity warfarin died

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Efficacy: Long-term, low-intensity warfarin therapy given with a target INR of 1.5–2.0 resulted in a large and significant reduction in the risk of recurrent VTE
Safety: The benefit of warfarin treatment was achieved with little evidence of any increase in the risk of major hemorrhage or stroke

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Ridker PM, Goldhaber SZ, Danielson E, Rosenberg Y, Eby CS, Deitcher SR, Cushman M, Moll S, Kessler CM, Elliott CG, Paulson R, Wong T, Bauer KA, Schwartz BA, Miletich JP, Bounameaux H, Glynn RJ, for the PREVENT Investigators. Long-term, low-intensity warfarin therapy for the prevention of recurrent venous thromboembolism. N Engl J Med 2003;348:1425-1434

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Corresponding author

Paul M. Ridker, MD, Center for Cardiovascular Disease Prevention, Brigham and Women’s Hospital, 900 Commonwealth Ave. East, Boston, MA 02215, e-mail:

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