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New research published in the online version of the Annals of Internal Medicine today documents an increased risk of heart attack with one of the COX-2 inhibitors used in elderly adults with no previous history of heart attack — a group previously considered low risk.

The study, sponsored by the Canadian Institutes of Health Research (CIHR) and conducted by researchers at the ³ÉÈËVRÊÓƵ Health Centre (MUHC) in Montreal, examined the relationship between the use of all nonsteroidal anti-inflammatory drugs (NSAIDs) and the risk of heart attack in 113,927 Quebec senior citizens. Only one of these agents, a COX-2 inhibitor called Vioxx — a new class of NSAIDs — carried a greater risk of heart attack.

"Many believe that COX-2 inhibitors increase the chance of a heart attack in high-risk groups, for example people who have already suffered a heart attack," explains primary author Linda Lévesque, a pharmacist and ³ÉÈËVRÊÓƵ PhD candidate in the Department of Epidemiology and Biostatistics. Lévesque worked with co-author Dr. James Brophy, a cardiologist and Director of the Technology Assessment Unit (TAU) at the MUHC and Associate Professor of Medicine at ³ÉÈËVRÊÓƵ. "This study demonstrates the overall risk of heart attack is increased 24% for users of Vioxx who have not previously suffered a heart attack," Lévesque says.

The study also reveals that aspirin use can help offset the damaging effects of Vioxx. "Aspirin mitigates the risk to individuals," confirms Lévesque, "but only in those on a low dosage of Vioxx."

The study also demonstrates that the increased risk of heart attack is only present while taking the drug. "Past users of Vioxx were not at increased risk," explains Lévesque, "while the risk more than doubles for those who are taking high doses of the drug even when using aspirin."

COX-2 inhibitors are commonly used to relieve the pain and inflammation caused by arthritis in the elderly. These drugs are believed to increase the "stickiness" of blood platelets — the tiny bodies that assist in blood clot formation. "It is possible that stickier platelets increase the chance of a blockage forming in a blood vessel of the heart," explains Lévesque. "This study contributes to the growing body of evidence concerning the cardiac safety of COX-2 inhibitors."

About the ³ÉÈËVRÊÓƵ Health Centre (MUHC)
The ³ÉÈËVRÊÓƵ Health Centre (MUHC) is a comprehensive academic health institution with an international reputation for excellence in clinical programs, research and teaching. The MUHC is a merger of five teaching hospitals affiliated with the Faculty of Medicine at ³ÉÈËVRÊÓƵ — the Montreal Children's, Montreal General, Royal Victoria, and Montreal Neurological Hospitals, as well as the Montreal Chest Institute. Building on the tradition of medical leadership of the founding hospitals, the goal of the MUHC is to provide patient care based on the most advanced knowledge in the health care field, and to contribute to the development of new knowledge.