Fine-tuning Therapy for Idiopathic Thrombosis

	After a first episode of idiopathic stroke, patients benefited so
much from taking extended anticoagulant therapy that researchers called an
early end to a trial of this treatment. Three months of warfarin (Coumadin)
use is not long enough for these patients with no known risk factors for
thrombosis, according to a study published in the New England Journal of
Medicine. Stopping blood thinner use early may place them at serious risk for
another stroke.
	The study involved 162 patients who had been taking warfarin for 3
months after a first episode of idiopathic venous thromboembolism (stroke).
Kearon and associates had patients either continue taking warfarin - with
dosing adjusted to achieve an INR (international normalized ratio) of 2-3.
or placebo. 79 patients continued warfarin and 83 took placebo.
	Although the study authors planned a 2 year follow-up, they halted
the trial after an analysis of effectiveness. By 9 month follow-up, 17
placebo patients had another confirmed episode of venous thromboembolism,
including one fatal pulmonary embolism; all episodes were idiopathic. In
contrast, only 1 of 79 patients still taking warfarin had such an epsiode
within one year follow-up.
	So extended warfarin therapy resulted in a 95% reduction in risk of
recurrent venous thromboembolism, the investigators concluded. Three patients
in the warfarin group had nonfatal major bleeding episodes, compared with
none of the placebo patients. However, the investigators felt the risk of
bleeding was "small when compared with the benefits of anticoagulant
therapy."
	How long therapy should be continued will require further study. In
an accompanying editorial, Andrew Schafer MD, suggests that once INR is
maintained between 2 and 3, warfarin might be given at less intense doses.
Schafer applauds the current study.

Clinician Reviews 9(6):138,139, 1999

Kearon C, Gent M, Hirsh J, et al. A comparison of three months of
anticoagulation with extended anticoagulation for a first episode of
idiopathic venous thromboembolism. N Engl J Med. 1999;340: 901-907

Schafer AI. Venous thrombosis as a chronic disease. N Engl J Med.
1999;340:955-956