A drug used worldwide to reduce bleeding during heart surgery can increase the risk of kidney failure, heart attacks and strokes, and should be abandoned, doctors are reporting today. They say other medicines are safer and cheaper, and should be used instead.

The drug, aprotinin, is sold under the brand name Trasylol and made by Bayer. The company disputed the new findings.

Heart surgeons said the new report, being published today in The New England Journal of Medicine, was important and persuasive, but not definitive. Although the drug has risks, they said, it may still be helpful in some surgical patients who have an unusually high risk of severe bleeding.

The Food and Drug Administration is examining the data on aprotinin, a spokeswoman, Susan Cruzan, said, "and will make recommendations for best use as soon as possible."

Aprotinin (pronounced a-PRO-ti-nin) has been on the market for 13 years. The report in the journal is based on a study of 4,374 patients having bypass surgery in Canada, Colombia, Europe, Israel, Mexico, Thailand and the United States. To limit blood loss, 1,295 were given aprotinin and 1,705 one of two other drugs, both generics, aminocaproic acid or tranexamic acid. A control group, 1,374 patients, had no drugs to prevent bleeding.

Compared with the other patients, those given aprotinin had twice the rate of kidney failure, 5 percent. They also had increases in other serious problems, including heart attacks, heart failure, strokes and a diffuse type of brain damage called encephalopathy.

The article said halting aprotinin use globally would prevent 10,000 to 11,000 cases of kidney failure a year and save more than $1 billion a year in dialysis costs, as well as nearly $250 million spent on the drug itself.

"It would be nearly impossible for me to recommend using the drug in this patient population," said Dr. Dennis T. Mangano, the director of the study and the founder of a group that paid for it, the Ischemia Research and Education Foundation.

Bayer said in a statement, "Bayer believes that Trasylol is a safe and effective treatment."

One potential flaw in the study is that the patients were not picked at random to have one treatment or the other. Rather, their doctors made the decision about which drug to use.

That means that in theory the groups could be skewed. Doctors might have assigned sicker patients to a particular drug that could make the results for that drug look especially bad.

On the other hand, the study was large, with copious figures collected for each patient in an effort to minimize biases.

"The study shows the drug has risks," said Dr. Gus J. Vlahakes, chief of the division of cardiac surgery at Massachusetts General Hospital, who wrote an editorial that accompanied Dr. Mangano's article. "You shouldn't give it to everybody having heart surgery."

Instead, Dr. Vlahakes said, it should be reserved for patients with unusual bleeding problems, because it works better at stopping bleeding than the other two drugs. At his hospital, with about eight heart operations a day, he said, Trasylol is probably used less than once a day.

Worldwide, about one million people a year have bypass surgery, and two-thirds to three-quarters of them are given Trasylol or one of the other two drugs to limit blood loss, Dr. Mangano said.

Use of Trasylol has varied, with some doctors favoring it and others avoiding it because of concerns that it may cause clots. Some doctors have also resisted using Trasylol because of its cost, more than $1,000 a patient, as opposed to $10 to $50 for the other drugs.

Last year, sales totaled $200 million. This year, Bayer projections are much higher, $600 million. In recent years, the company has been marketing Trasylol to prevent inflammation, as well as bleeding, in bypass patients.

Its Web site suggests using the drug in all patients put on heart-lung machines for bypass surgery and explains the drug's role in inhibiting inflammation.

Dr. Vlahakes said preventing inflammation might require higher doses of the drug than those now being used. In view of the new safety information, he said, "I think there's no way" that the drug could be so broadly used, particularly at higher doses.

Bayer is also studying Trasylol in hopes of having it approved to prevent blood loss from hip replacement and spinal surgery.

Currently, Trasylol is given to heart-surgery patients intravenously along with a plethora of other medicines, and most people do not even know that they are receiving it. Doctors do not need special permission to administer it.

Given his findings, Dr. Mangano said, doctors should warn patients about the potential risks and ask for their consent to use it.

"I cannot see how a patient would elect to use this drug as opposed to the others," he said.

Dr. Timothy J. Gardner, the medical director of the Center for Heart and Vascular Health at the Christiana Care Health System in Newark, Del., and a spokesman for the American Heart Association, said the article would have substantial effects on medical practice.

Dr. Gardner said the findings were worrisome because many patients had been taking other drugs that increased the tendency to bleed, and surgeons sometimes need all possible help to stop excess blood loss.

Dr. Vlahakes agreed. "It's 2 o'clock in the morning and you can't stop the bleeding," he said. "That's every surgeon's nightmare."