Long-term anticoagulation for venous thromboembolism: duration of treatment and management of warfarin therapy.

Treatment of venous thromboembolism (VTE) should be continued until the reduction of recurrent VTE that anticoagulation is expected to achieve no longer outweighs the increase in bleeding associated with therapy, or until the patient wants to stop treatment even if treatment is expected to be of benefit. Reversibility of risk factors for VTE is the most important factor that influences risk of recurrence and duration of therapy. VTE associated with a reversible risk factor (eg, surgery) is treated for 3 months; unprovoked VTE often benefits from indefinite therapy provided patients do not have risk factors for bleeding; and cancer-associated VTE is usually treated indefinitely. A systematic approach to managing warfarin therapy improves its efficacy, safety, and acceptability.