Patients suffering from acute coronary syndrome who stop taking clopidogrel (Plavix) may be more likely to die or to suffer an acute myocardial infarction especially in the first 90 days after cessation, researchers say.

Plavix, manufactured by Bristol-Myers Squibb Co. and Sanofi-Aventis SA, is an antiplatelet drug, which discourages the formation of blood clots and helps prevent heart attacks and strokes caused by clots.

Dr. P. Michael Ho of the Denver Veterans Affairs Medical Center and colleagues analyzed 3.137 veterans with acute coronary syndrome who had been prescribed Plavix after they had been treated either with a stent to open a blocked artery or a combination of medicines designed to manage their heart disease. Almost all of the patients, 98 percent, were men.

After stopping Plavix, the patients were followed for nearly seven months. Seventeen percent of them who had only gotten drug treatment and 8 percent of those who had gotten stents died or had a heart attack. Most of those cases, 60 percent, happened in the first 90 days after stopping Plavix, regardless of how their initial heart episode was treated.

“We looked at people who took different length of clopidogrel treatment. We found a twofold increase in risk in the 90-day period after stopping for those who [took it] less than six months or greater than nine months. For those who took clopidofrel longer than 12 months or 15 months, we could not calculate the increased risk because we did not have enough patients,” Dr. Ho said in the study.

Dr. Ho said that the findings do not offset the benefits of Plavix use. However, if these results are confirmed by other studies, doctors may need to see if patients should take Plavix longer, taper off Plavix, or use other drugs to lower death and heart risk, the researchers wrote.

“The final decision should be left to provider and patient. They have to weigh the risk of discontinuing clopidogrel against the risk of abnormal bleeding if it is continued. The clinician needs to weigh the risk and benefits for each individual patient,” Dr. Ho said.

About 775,000 people have mild heart attacks or chest pain known as acute coronary syndrome in the United States each year.

The study, funded by the Quality Enhancement Research Initiative of the Department of Veterans Affairs, appeared in the February 6 issue of the Journal of the American Medical Association.