Chicago ? Heart attack patients are often given overdoses of powerful blood-thinning drugs in the emergency room, increasing their risk of serious bleeding, a study found.

Of the 30,136 heart attack patients studied who were treated last year at 387 U.S. hospitals, 42 percent got excessive doses of blood thinners. Overdoses were particularly common in thin people, women, the elderly and those with kidney problems.

Those given too much of two newer blood thinners – low molecular weight heparin and drugs sometimes called “super-aspirin” – had more than a 30 percent increased chance of major bleeding than those given the recommended dose.