Low-intensity warfarin therapy fails to impress
Debate about the intensity of warfarin therapy that should be used to prevent recurrent venous thromboembolism may have been settled this week with publication of a study in The New England Journal of Medicine (2003;349:631).
Dr Clive Kearon, McMaster University, Hamilton, Ontario, and colleagues
hypothesised that extended treatment with low-intensity anticoagulant
therapy (target international normalised ratio [INR] of 1.5 to 1.9) might
be as effective as conventional-intensity therapy (target INR of 2.0
to 3.0) but with a lower risk of bleeding. However, in a study of 738
patients, they found that not only was conventional treatment more effective,
it was also no more likely to cause bleeding episodes than low-intensity
therapy.
The researchers conclude that low-intensity therapy reduces the risk
of recurrent thrombosis by about 75 per cent, whereas conventional-intensity
therapy reduces this risk by over 90 per cent.
The authors of an accompanying editorial point out that a recent
study comparing low-intensity warfarin with placebo had shown the active treatment
to be “a highly effective method of preventing recurrent venous
thromboembolism” (PJ, 1 March, p292). The rates of thrombosis recurrence
and bleeding were similar to those observed in the current study and
so when considered together suggest that conventional therapy is preferable. “It
appears the debate about the intensity of warfarin therapy for venous
thromboembolism is now settled. The target INR should be 2.0 to 3.0,” they
conclude (ibid, p702). |
