Vioxx risks highest in first two weeks
The blockbuster drug Vioxx was pulled from the market in the fall of 2004 after research showed that the painkiller doubled the risk of heart attack and stroke and that its use may have contributed to thousands of deaths in North America.
Now, a new Canadian study shows that the risk was even more dramatic because one in four of the heart attacks that occurred were within two weeks of the start of treatment.
“This demonstrates that cardiovascular risks from taking Vioxx may occur much earlier than previously believed,” said Linda Lévesque, an assistant professor in the department of community health and epidemiology at Queen’s University in Kingston.
At the same time, however, the research shows that additional risk virtually disappears within a month, meaning it is likely safe for long-term use.
The earlier data had suggested that the risk remained elevated for up to 18 months.
The research was published yesterday in the on-line edition of the Canadian Medical Association Journal.
Peter Liu, scientific director of the institute of circulatory and respiratory health of the Canadian Institutes for Health Research, said the study “adds important new information on how the Cox-2 inhibitors like Vioxx affect the heart.”
Rofecobix, which was sold under the brand name Vioxx, is one of a class of drugs known as Cyclo-oxygenase-2 inhibitors.
(The Cox enzyme has two forms in the body: Cox-1 protects the stomach lining from harsh acids and digestive chemicals, while Cox-2 is produced when joints are injured or damaged.)
One Cox-2 inhibitor, celecoxib, sold under the brand name Celebrex, is still available in Canada. Research has shown that Celebrex does not appear to increase cardiovascular risk in the same way as Vioxx and Bextra (valdecoxib), which was pulled from the Canadian market in April, 2005.
Data for the new study, conducted while Dr. Lévesque was a doctoral student at McGill University, were drawn from a database of 125,000 Quebec senior citizens who were prescribed painkillers between 1999 and 2002, and about one-quarter of whom were deemed “current users.”
Their average age was almost 79.
Researchers found that 239 current users of Vioxx and 287 current users of Celebrex suffered heart attacks — not an uncommon occurrence in this age group.
However, the risk of a heart attack rose sharply in the two weeks after first-time use of Vioxx, which was not the case with Celebrex.
An expert advisory panel, struck by Health Canada, had recommended last year that Vioxx be allowed to return to the market in Canada, but that has not occurred.
The panel also said that all anti-inflammatory drugs, including non-prescription painkillers such as ibuprofen, should have much stronger health warnings.
In the United States, the maker of Vioxx, Merck & Co. Inc., has been fighting thousands of lawsuits related to the drug.