An analysis of an infamous Vioxx study found the notorious painkiller does, indeed, double the risk of heart attacks and strokes, although the likelihood of a serious cardiovascular event lessened one year after people no longer took the pill. What's more, other drugs in the same class, known as Cox-2 inhibitors, may pose the same risk, according tothe analysis published in The Lancet.
"The good news is the data suggests that the risk doesn't persist forever. The risk goes back toward normal after a year of follow up," Robert Bresalier of the MD Anderson Cancer Center at the University of Texas, one of the study authors, tells Reuters.
The original study, known as Approve, was funded by Merck and designed to determine whether Vioxx could prevent polyps that increase the risk of colon cancer. Instead, the Approve study caused concern that Vioxx increased cardiovascular risks and prompted Merck to withdraw the pill in September 2004.
Interestingly, a 2005 analysis by Bresalier and other researchers that was published in The New England Journal of Medicine suggested it took 18 months for Vioxx to increase the risk of heart attacks and strokes. As Reuters notes, that time frame played a big role in Merck's legal defense, although the journal later posted a correction on its Web site, saying the difference was not statistically significant.
The new analysis, done with independent statisticians, suggests the risk occurs early and persists, according to Bresalier. "This data shows you can't precisely determine the timing of the risk. It does appear to start relatively early," he tells Reuters.
The Approve study looked at the effects of three years of treatment with Vioxx in 2,587 patients, who were checked for side effects while on the drug and two weeks after they stopped, and included one-year follow-up data on patients who stopped taking the drug because of cardiovascular side effects. "In essence, the relative risk remained about the same," Bresalier tells Reuters.
People who took Vioxx in the study had about the double the risk of having a heart attack or stroke than those who took a placeob.
In a statement, Merck says the overall findings were consistent with the Approve study, but not all patients were able to be followed after they stopped taking the drug and that risk factors for cardiovascular events may have changed after patients stopped taking the drug. Research "using limited data from a prematurely terminated study needs to be interpreted very cautiously and in the context of the rest of the data from the extensive clinical development program for Vioxx."
Meanwhile, Bresalier tells Reuters that a number of studies since the initial safety warning on Vioxx suggest other Cox-2 inhibitors, including Pfizer's Celebrex and non-steroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen, also carry a higher risk of heart trouble.
"I think the preponderance of data now does suggest this is a class effect," he tells Reuters. "There seems to be an increased risk for most if not all non-steroidal anti-inflammatory drugs. That doesn't mean these aren't good drugs. It's just there is some increased risk we need to be aware of."