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Health Canada Warns About Use of Pain Killer Celebrex Due to Heart Risk

Posted on: Saturday, 18 December 2004, 03:00 CST

TORONTO (CP) - Health Canada has pulled authorization of pain relief drug Celebrex for the treatment of a rare genetic disease, following "new information" linking the drug to an increased risk of heart attack.

The department has withdrawn authorization for Pfizer Inc., to market the drug for the treatment of Familial Adenomatous Polyposys, a disease "highly predictive" of colorectal cancer, spokesman Ryan Baker said late Friday.

"Celebrex should not be taken for the prevention of recurrence of this condition (FAP) and patients should discuss alternative therapies with their doctors," Baker said in an interview from Ottawa.

The new restriction followed Friday's announcement by Pfizer that Celebrex appears to raise the risk of heart attack in users.

Baker said those patients should consult their doctor about alternative treatments. The drug is still approved in Canada for the treatment of other conditions, such as rheumatoid arthritis and acute pain.

Though Pfizer said Friday it would not pull the drug from the market, the news left in doubt not just its future but the future of the entire class of drugs known as cox-2 inhibitors - massive money spinners that stormed the market five years ago.

"There's a growing concern that in predisposed patients the class of drugs called cox-2 inhibitors may increase the risk of cardiovascular events, possibly varying in degree from drug to drug," said Dr. Arthur Bookman, a rheumatologist at Toronto Western Hospital and head of the Arthritis Society's medical advisory board.

Pfizer announced Friday that two U.S. National Cancer Institute trials looking at Celebrex as a potential cancer preventer were stopped when one showed people taking the drug were 2.5 times more likely to have a major cardiovascular event, including death.

The cancer study involved doses of between 400 and 800 milligrams a day, higher than most people would take.

Merck and Co. pulled competitor drug Vioxx from the market in September over similar concerns and Pfizer's Bextra is also under fire after showing signs of increased cardiovascular risk among some users.

In the wake of Pfizer's announcement, the Arthritis Society and Health Canada urged people taking cox-2 drugs to consult their health-care providers - especially those taking high daily doses.

While that advice appeared to be universally supported, the early - and mixed - reaction of a group of experts suggested those doctors won't have definitive answers, either.

Some were suggesting the drugs be avoided if at all possible. Others said only patients at high risk of heart attack or stroke be switched to older, over-the-counter medications like acetaminophen. Others theorized the high doses used in the cancer trial might indeed be the problem and lower doses might be safe.

But Dr. Garrett FitzGerald, a cardiologist and pharmacologist, said the findings put to rest questions over whether the heart health risks associated with Vioxx were unique to that drug or were consistent across the cox-2 class.

"Either you are a devoted believer in a series of horrible coincidences or else you buy into the fact that the class-based mechanism which explains how these drugs work also cuts across the class to explain how they manifest adverse cardiovascular events," said FitzGerald, a University of Pennsylvania expert who has been studying the drugs since before they came to market.

Still, FitzGerald didn't advise consigning cox-2s to the pharmaceutical waste basket. He suggested anyone at high risk of heart problems should avoid the drugs and others should weigh risks and benefits with their doctors.

He insisted, though, that cox-2s were not likely to pose a risk to people in good heart health and more research should be done to find ways to identify who can safely use them.

"For people at low cardiovascular risk, it's almost certain that taking these drugs for short periods of time is unassociated with any hazard that we can measure," FitzGerald said.

Dr. Muhammad Mamdani also advised caution in interpreting the findings.

A doctor of pharmacy and a senior scientist at Toronto's Institute for Clinical Evaluative Sciences, Mamdani noted other studies of Celebrex - including the second cancer trial - have not shown this risk.

"This whole decision . . . should not be based on one trial. It should be based on the bulk of evidence that's out there," he said.

"My recommendation to patients would be 'Don't necessarily throw your Celebrex pills in the garbage. I think that would be a big mistake.' "

He did stress that patients on cox-2s should take the lowest possible dose for the shortest possible time.

But Dr. Mark Fendrick, an internal medicine specialist who previously advocated a weighted risk-benefit approach to cox-2s, said it's time to move to other drugs.

"I would not recommend their use until we know for sure about their cardiovascular safety, till we have evidence that there's an absence of risk," said Fendrick, an internal medicine specialist at the University of Michigan Health System in Ann Arbor, Mich.

"And that's extraordinarily unlikely."

Source: Canadian Press

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