Do doctors prescribe too much aspirin for heart attack patients? A lower dose may be as effective--and safer--than a higher dose.

Taking aspirin during a heart attack saves lives. This cheap, common drug can halt the formation of blood clots and ease blood flow through the coronary arteries. For this reason, doctors often give aspirin to suspected heart attack victims immediately upon their arrival in the emergency department.

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But doctors may be giving patients too much aspirin, and this may do as much harm as good. A study spearheaded by Duke university Medical Center physicians and published in the January issue of Circulation found that 162 mg of aspirin (equivalent to two baby aspirin) produced the same benefit as 325 mg (one adult aspirin), but with significantly less risk of internal bleeding. (The Duke study was an analysis of two earlier studies: The Global utilization of streptokinase and Tissue Plasminogen Activator for occluded Coronary Arteries (GUSTO 1) and Global use of strategies to open occluded Coronary Arteries (GUSTO III) studies, both conducted in the 1990s.)

THE PROS AND CONS OF ASPIRIN. A study published in 1988 found that a single 162 mg-dose of aspirin can improve the chance of surviving a heart attack by 23 percent and reduce the risk of subsequent nonfatal heart attack and stroke. As a result, the American Heart Association (AHA), American College of Cardiology (ACC) and European society of Cardiology (ESC) recommended a dose of 162 mg for treatment of heart attack. Conversely, there is little evidence to support the use of a 325 mg dose.

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The antiplatelet properties that make aspirin so effective in heart attack also are responsible for its most common side effect: internal bleeding; the higher the dose of aspirin, the greater the chance of bleeding in the stomach or intestines. Bleeding may also occur in the brain or elsewhere in the vascular system. This is why patients who take other blood thinners; have a bleeding disorder, uncontrolled hypertension, stomach ulcers, liver or kidney disease; or are pregnant should never take aspirin--even during a heart attack --unless directed by their doctor.

Because aspirin's effects are systemic, the drug can be effective in stroke as well as heart attack. However, because some strokes are caused by bleeding into the delicate tissues of the brain, patients should never take aspirin during a stroke until this underlying cause has been ruled out.