Heart Patients Warned Against Using Meridia, an Anti-Obesity Drug

European and American drug regulators had two starkly different reactions this week to data on an obesity drug. The raw data from the study indicated that people with certain health problems who took the prescription diet drug Meridia had more heart attacks, strokes and other cardiovascular problems than people getting a placebo.

On Thursday, the European Medicines Agency advised doctors and pharmacists to stop prescribing and dispensing European equivalents of Meridia. The Food and Drug Administration, looking at the same study data on Thursday, took a less forceful step and asked Abbott Laboratories, the maker of Meridia, to put a stronger warning on its label.

The F.D.A. said the new warning should indicate that the drug was not to be used by people who have a history of heart attacks or strokes, or who have uncontrolled high blood pressure.

Abbott, which sells Meridia in Europe under various brand names, including Reductil and Ectiva, indicated Friday that it would comply with the F.D.A.’s labeling request and with the European advisory by suspending sales of the drugs in Europe.

Meridia contains the ingredient sibutramine, which works by increasing neurotransmitter activity in the brain, helping people to feel full after a meal and thereby reducing their food intake. The company said the drug was safe and effective when used in appropriate patients.

“We believe there are many patients who benefit from sibutramine,” Dr. Eugene Sun, vice president for global pharmaceutical research and development at Abbott, said in a statement.

The company’s global sales of sibutramine drugs last year were about $300 million, although usage in the United States has been declining for years.

The study, called the Scout trial, is important for the field of obesity as a whole because its findings contradict what has been the long-held presumption — that weight-loss drugs are more than just cosmetic. The presumption has been that they will actually help reduce the serious health problems, like heart disease, that are associated with obesity.

The Scout study was the first to actually test this presumption, to see if a diet drug could reduce the risks of heart attacks.

Some experts said the finding that Meridia actually increased such risk in some high-risk patients rather than reduce it could raise questions about the safety of other diet drugs.

The findings might also raise the safety hurdle for new obesity drugs to win approval. However, some experts said the problems might be unique to Meridia, which clearly raises blood pressure and heart rate.

In any case, the significantly different actions by the two health authorities is stirring debate among drug makers and consumer advocates. Did the European agency act too quickly on a set of preliminary data — or was it moving more forcefully to defend consumer health than its American counterpart?