Aspirin therapy has proven useful in preventing Heart attacks, but even very low doses of the drug taken regularly pose a bleeding risk, according to new research.

The findings also suggest that in terms of causing bleeding problems, moderate aspirin doses may be just as bad as high doses. In addition, moderate doses increase the risk of stomach bleeding and Stroke compared with low doses.

“We all know aspirin in general is associated with bleeding risk; a variety of trials and (review studies) proved that,” Dr. Victor L. Serebruany told. But the effects of the aspirin dose on this risk were unclear.

Serebruany, from the HeartDrug Research Laboratories in Towson, Maryland, and colleagues analyzed data from previous studies, focusing on the effect that the aspirin dose has on bleeding risk. Their findings appear in the American Journal of Cardiology.

Their study encompassed data from 31 clinical trials, which involved a total of 192,036 patients. Patients were divided into three groups depending on their daily aspirin dose: low (less than 100 mg), moderate (100 to 200 mg), and high (greater than 200 mg).

According to the team’s report, the rate of bleeding problems ranged from 3.7 percent in the low-dose group to 11.3 percent in the moderate-dose group. The high-dose group had a rate of 9.8 percent, which although lower, was statistically comparable to the rate in the moderate-dose group.

The rate of fatal or life-threatening bleeding problems in the low-, moderate-, and high-dose groups was 0.27, 0.46, and 1.59 percent, respectively. Moderate doses also caused significantly higher rates of stomach bleeding and stroke compared with the low doses.

“Low doses were OK, but doses over 100 are (comparable) with those over 300,” Serebruany said. This is important, he pointed out, since in Europe the standard aspirin dose given to patients with heart disease is 150 mg.

“Until we have more reliable evidence, the lower the dose of aspirin we have available the more chance we will be safe using it,” he concluded.

SOURCE: American Journal of Cardiology, May 15, 2005.