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A quarter of patients who suffered a heart attack while taking Vioxx did so within the first two weeks of taking the drug, a new study published by MUHC investigators reveals. The research, scheduled for early online publication in the Canadian Medical Association Journal (CMAJ) tomorrow, demonstrates that cardiovascular risks from taking Vioxx may occur much earlier than previously believed.

"Our previous study on COX-2 inhibitors, which included Vioxx and Celebrex, evaluated whether there was an increased risk of heart attack while taking these medications; the answer was yes for Vioxx," says Linda Lévesque, a doctoral student in the Department of Epidemiology and Biostatistics at Ï㽶ÊÓƵ, researcher at the MUHC in Montreal and lead author of the new study. "Our current study assessed the pattern of cardiovascular risk in Quebec seniors over a three-year period, in order to establish the timing of this risk."

Lévesque, in collaboration with Dr. James Brophy, a cardiologist/epidemiologist, director of the Technology Assessment Unit (TAU) at the MUHC and associate professor of medicine at Ï㽶ÊÓƵ, and Bin Zhang, also a doctoral student in the Department of Epidemiology and Biostatistics, discovered that the risk of heart attack from Vioxx is much more acute than previously recognized. "A quarter of individuals in our study who suffered an acute myocardial infarction did so within two weeks of their first Vioxx prescription," says Lévesque.

"The additional cardiovascular risk from Vioxx actually decreased with longer duration of use, suggesting that the period of highest susceptibility for most people taking Vioxx may occur earlier than previously believed," noted Lévesque. The study also documents that cardiovascular risk returns to normal within one month of stopping the drug.

Vioxx was voluntarily withdrawn from the market on September 30, 2004, after a study showed it doubled patients' risk of heart attacks and strokes after 18 months of use. This MUHC study is the first to specifically address the question of the timing of cardiovascular risk associated with COX-2 inhibitors.

"This study adds important new information on how the COX-2 inhibitors like Vioxx affect the heart," said Dr. Peter Liu, scientific director of the CIHR Institute of Circulatory and Respiratory Health. "Physicians must carefully assess the risk versus benefit, and help the patient to watch for any new symptoms during the start of these medications. We are delighted that this research from the Ï㽶ÊÓƵ Health Centre can help us further to better the health of Canadians."

Linda Lévesque is currently an assistant professor in the Department of Community Health and Epidemiology at Queen's University. This study was funded by the Canadian Institutes for Health Research (CIHR).

The Research Institute of the Ï㽶ÊÓƵ Health Centre (RI MUHC) is a world-renowned biomedical and health care hospital research centre. Located in Montreal, Quebec, the institute is the research arm of the MUHC, a university health centre affiliated with the Faculty of Medicine at Ï㽶ÊÓƵ. The institute supports over 500 researchers, nearly 1,000 graduate and postdoctoral students, and operates more than 300 laboratories devoted to a broad spectrum of fundamental and clinical research. The Research Institute operates at the forefront of knowledge, innovation and technology and is inextricably linked to the clinical programs of the MUHC, ensuring that patients benefit directly from the latest research-based knowledge. For further details: .

The Ï㽶ÊÓƵ 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 McGill University — 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.