The US Food and Drug Administration approved the use of Bristol-Myers Squibb's blockbuster antiplatelet drug Plavix for patients who have had a type of heart attack called acute ST-segment elevation myocardial infarction (STEMI), and who are not going to have coronary artery repair via angioplasty.

But reaction to the news was inevitably muted, given that B-MS and its partner for Plavix (clopidogrel), Sanofi-Aventis, are still reeling from the start of generic competition to the drug from Canadian company Apotex. Any change to the labelling for Plavix will also benefit the copycat version, at least until the patent infringement case brought against Apotex comes to its conclusion.

B-MS and Sanofi, which insists they have patent protection for Plavix out to 2011, asked for a preliminary injunction against the sale of Apotex’ generic earlier this week, and are due to hear a verdict on this request later today.

According to the American Heart Association, each year an estimated 500,000 Americans have a STEMI heart attack, or around a third of the total number of cases each year.

"Plavix has demonstrated that it can help reduce these post-STEMI events for patients who suffer certain kinds of heart attacks," said Steven Galson, Director of the FDA's Center for Drug Evaluation and Research.

Two studies – COMMIT and CLARITY - support the effectiveness of Plavix in treating STEMI heart attack patients.

Results of the COMMIT trial showed that 28 days after treatment was initiated, Plavix taken on top of aspirin and standard therapy reduced the relative risk of death in STEMI patients by 7%, and cut the risk of the combination of a heart attack, stroke or death by 9%.

In the CLARITY trial, Plavix plus aspirin and other standard therapy including thrombolytics significantly reduced the odds of STEMI patients having another occluded artery, or a second heart attack or death by 36% by day eight of hospitalisation or discharge.