Long-term, low-intensity warfarin after idiopathic venous thromboembolism.

Background: Current guidelines recommend that full-dose warfarin be continued for 6–12 months after an idiopathic episode of venous thromboembolism (VTE), with a target international normalized ratio (INR) of between 2.0 and 3.0. The annual risk of major hemorrhage in patients prescribed warfarin is 5%–9%, whereas the long-term risk of recurrent VTE after cessation of anticoagulation is 6%–9% per year, and may be as high as 10%–27% in the first 12 months following cessation of warfarin for idiopathic deep vein thrombosis (DVT). Low-intensity warfarin (INR 1.5–2.0) may carry a lower risk of bleeding and appears to suppress biochemical markers of coagulation; however, this strategy to prevent recurrence of VTE has not been tested in randomized controlled trials.