Labels on the heart surgery drug Trasylol will carry stronger warnings about increased risk of kidney damage, the U.S. Food and Drug Administration announced Friday.

Trasylol, or aprotinin injection, is given to patients before heart surgery to reduce bleeding and the need for blood transfusions.

"The purpose of the label change is to inform physicians and patients about the risks associated with Trayslol and to ensure they understand the new warnings and use the product as directed by the label," Dr. Steven Galson, head of FDA's center for drug evaluation and research, said in a statement.

In the U.S., the label on Bayer's drug warns that use of the drug should be limited to those at increased risk of blood loss during coronary bypass graft surgery when a machine takes over the heart's functions during surgery. The operation is performed to improve blood flow to the heart.

Health Canada approved the use of Trayslol as an intravenous solution in 1995, according to the department's online database.

Preliminary data given to the FDA from the company suggested Trayslol could increase the risk of death, congestive heart failure and strokes.

Published studies also reported an increase in the possibility of kidney failure, heart attack and stroke in patients treated with Trayslol compared with other drugs. Another study reported an increased risk of kidney damage compared with other drugs.

The new label warns of possible risk for kidney damage, and suggests ways to manage and reduce the patient's risk of exaggerated immune reactions.

The regulator became aware of the safety information after the drug was introduced on the market.

Staff at the FDA began reviewing safety data on Trasylol in January 2006 after the two studies were published.