Drug treatment after blood clots

How long should patients take anti-clotting drugs after an episode of venous thromboembolism?

That’s the question researchers set out to answer in a new study published in the Archives of Internal Medicine. They reviewed 18 major studies on the use of vitamin K antagonists — drugs such as Coumadin — that help patients who have had a dangerous blood clot avoid the development of another blood clot. Their review shows the risk of recurrence generally stabilizes after about nine months.

People who experience venous thromboembolism are first treated with the blood thinner heparin for about five to 10 days to resolve the clot. Doctors usually add a vitamin K antagonist to the mix within 48 hours as well, to prevent recurrence. This therapy is generally continued for three to six months. Some patients at especially high risk for recurrence may stay on the treatment longer. Since bleeding is a concern with the treatment, researchers wanted to determine whether prolonged treatment is really necessary.

The meta-analysis found monthly recurrence of venous thromboembolism was high immediately after discontinuation of treatment, regardless of whether the patients had been on the therapy for a short, medium, or long duration. However, recurrent episodes declined rapidly thereafter, with the monthly incidence after nine months about the same regardless of how long patients had received the therapy initially.

Authors conclude continuation of vitamin K antagonist therapy beyond three months should be considered with caution. They write, “It is questionable whether the reduced risk of a recurrent venous thromboembolic event when vitamin K antagonist treatment is prolonged can counterbalance the burden of treatment and the increased risk of bleeding, with its often far-reaching consequences for the quality of life for the patient.”

SOURCE: Archives of Internal Medicine, 2003;163:1285-1293