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Prime-time clot-busting.

Although most heart attacks strike in the morning, a new study indicates that a clot-busting drug works best in the afternoon. This finding, if confirmed, suggests that the body's circadian rhythm may affect the efficacy of drugs.

Cardiologist Peter Kurnik of the Robert Wood Johnson Medical School branch in Camden, N.J., studied 692 men and women who received tissue plasminogen activator (TPA) within six hours of suffering a heart attack. TPA and other thrombolytic drugs work by dissolving the jelly-like blood clot that blocks a coronary artery. Kurnik discovered that people who received TPA between noon and midnight had a better chance of their clot dissolving than did people who got the drug in the morning.

Kurnik notes that TPA-inhibiting substances that occur naturally in the blood reach a zenith in the morning, and that blood components called platelets are stickier in the morning, making it harder for TPA to do its job. "I strongly suspect that you need a higher dose of TPA in the morning," he says.

At the same time, Kurnik says people who get chest pains in the morning can't afford to wait until their biological clock signals an optimal time for TPA injection.

"No matter what time of day you have a heart attack, it's best to get treatment early, preferably within two hours," Kurnik says.

While early treatment remains a crucial message, many female heart attack victims may not receive clot-busting drugs at all, according to the results of a separate study. Charles Maynard and his colleagues at the University of Washington in Seattle studied 1,659 women and 3,232 men treated for heart attacks at 19 Seattle-area hospitals. While 26 percent of the men received clot-busting drugs, such as TPA, only 14 percent of the women got this lifesaving therapy. Those findings raise the possibility of some bias against using the drugs to treat women suffering from heart attacks, Maynard says.
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Title Annotation:Biomedicine
Author:Fackelmann, Kathy A.
Publication:Science News
Article Type:Brief Article
Date:Nov 23, 1991
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