Low-dose warfarin and aspirin no more effective than aspirin alone after AMI

NEW YORK (Reuters Health) – The results of a randomized trial show that secondary prevention after and acute myocardial infarction (AMI) with a combination of low-dose warfarin and low-dose aspirin is no better at preventing a second MI or stroke than a standard dose of aspirin alone, according to a report in the February 5th issue of Circulation: Journal of the American Heart Association.

In an interview with Reuters Health, co-author Dr. Louis Fiore from the Boston Veterans Administration Healthcare System stressed that "these results should not be misinterpreted, because the dose of both aspirin and aspirin were attenuated, from a fear that standard doses would induce too much bleeding."

"Had we used a more intense warfarin regimen, then we may have seen more bleeding. But we would likely have seen an additive effect with the aspirin," he continued. "I can say that now, because two unpublished European studies have shown a benefit from the combination of drugs with standard doses of warfarin and low-dose aspirin; and the incidence of bleeding was acceptable." (see Reuters Health report September 3, 2001)

Dr. Fiore and associates from the Combination Hemotherapy and Mortality Prevention Study (CHAMP) group studied 5059 AMI patients. Within 2 weeks after infarction, the patients were randomly assigned to 1.5 to 2.5 IU warfarin plus 81-mg aspirin daily or to monotherapy with 162-mg aspirin daily. The primary endpoint was total mortality; the secondary endpoints included recurrent MI, stroke and major bleeding.

After a median of 2.7 years of follow-up, 17.3% of the patients receiving aspirin monotherapy and 17.6% receiving combination therapy died (log-rank p = 0.76). Recurrent MI occurred in 13.1% of the patients on aspirin therapy and in 13.3% of patients on aspirin and warfarin (log-rank p = 0.78). Stroke occurred in 3.5% of those receiving aspirin and in 3.1% of the patients on combination therapy (log-rank p = 0.52), the researchers found.

Patients on the combination regimen experienced more major bleeding (rate ratio 1.78) compared with patients receiving aspirin alone, the investigators note.

Dr. Fiore concludes that "the only value of this study is that it answers the question [of] whether low doses of warfarin work in AMI patients. And the answer is no."

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