Duration of Anticoagulant Therapy in Venous Thromboembolism

A Cochrane review [Abstract] 1 included 11 studies with a total of 3 716 subjects. The studies compared the following different periods of treatment with vitamin K antagonists (VKA): 4 weeks versus 3 months, 6 weeks versus 12 weeks, 6 weeks versus 6 months, 3 months versus 6 months, 3 months versus one year, 3 months versus 27 months, 4 months versus 27 months, 6 months versus 30 months, and 6 months versus 4 years.

Prolonged treatment with vitamin K antagonists resulted in a consistent reduction for the risk of recurrence of venous thromboembolism (VTE) independent of the period elapsed since the index thrombotic event. Comparisons of two specific durations are shown in table T2. A statistically significant rebound phenomenon (ie, an excess of recurrences shortly after cessation of prolonged treatment) after cessation of treatment was not observed (OR 1.28, 95% CI 0.97 to 1.70). No statistically significant reduction in mortality was noted. Substantial increase in bleeding complications was observed for patients receiving prolonged treatment (table T1).