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Clot-blocking drug prevents heart attacks

A new anti-clotting agent modeled after a snake venom could prevent as many as 40,000 heart attacks and 10,000 deaths each year if it were used routinely.

The new drug _ tirofiban _ reduces heart attacks and deaths by half in patients with so-called unstable angina, the most common cause of hospital admissions in the United States, physicians told a meeting of the American College of Cardiology. Such patients come to emergency rooms with all the symptoms of a heart attack, but their coronary vessels are not completely clogged and they do not require clot-busting drugs such as tPA.

Untreated, many of these people would have heart attacks. With the best available blood thinning therapy now _ aspirin and heparin _ nearly 1 in 10 has a heart attack during their hospital stay.

Administration of the new drug, along with aspirin and heparin, prevents the clot from growing any larger, reducing the risk of heart attack and giving physicians time to decide if angioplasty or bypass surgery is necessary.

"This is a breakthrough study," said Dr. H. Vernon Anderson of the University of Texas in Houston. "To reduce deaths by 50 percent is very dramatic. This drug gives us a great opportunity to make meaningful reductions in the number of heart attack deaths."

Representatives of Merck & Co., which manufactures the drug under the trade name Aggrastat, said the company plans to apply to the Food and Drug Administration later this year for permission to market it. A related drug, ReoPro produced by Centocor Inc., has already been approved by FDA to prevent clot formation during angioplasties.

Unstable angina occurs when a fatty buildup on an artery wall breaks open during some form of stress. Blood cells called platelets congregate in this wound and clump together. In the narrow confines of an artery, this clot can be disastrous.

The anti-clotting drugs would be used almost as soon as the patient shows up at the hospital. Tirofiban buys time for heart specialists to determine the best treatment for the patient, said molecular biologist Rick Sax of Merck, who developed the drug.

_ Information from the Associated Press was used in this report.