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Health Canada Warns Consumers About Use of Drug Celebrex Due to Heart Risk

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

TORONTO (CP) - Health Canada has told the maker of Celebrex it can no longer market the pain reliever for the treatment of a rare genetic disease, a spokesman for the department said late Friday.

Spokesman Ryan Baker said the department has withdrawn authorization for pharmaceutical giant Pfizer Inc., to market the product for the treatment of Familial Adenomatous Polyposys, effective immediately.

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

The warning to consumers follows the release of "new information" about the increased risk of heart attack in users taking daily doses of 400 milligrams and 800 milligrams, Baker said.

Health Canada said Celebrex should not be taken to deal with this condition, which Baker described as being "highly predictive" of colorectal cancer.

On Friday, those suffering from chronic pain were again faced with uncertainty and anxiety with the news that Celebrex appears to raise risks of heart attack in users.

Though Pfizer said 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 just 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.

Merck and Co. pulled competitor drug Vioxx from the market in September over similar concerns and Pfizer's Bextra is also under fire having shown 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.

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

"As a precaution, Health Canada is advising that patients using 400 mg per day or 800 mg per day doses should discuss with their health professional whether the risk of cardiovascular side-effects outweighs the benefits," the department said in a release earlier in the day.

While the advice to consult one's doctor 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 had 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."

Dr. Claire Bombardier, head of rheumatology at the University of Toronto medical school, said she would be switching high risk patients off cox-2s.

"At this point, given the results of this new trial, if I had somebody who was at cardiovascular risk, that I would switch them back to a traditional NSAID, plus a medication to protect the stomach."

But Bombardier noted that there isn't really any evidence that traditional NSAIDs - non-steroidal anti-inflammatory drugs such as acetaminophen or ibuprofen - don't cause the same problems. Those studies simply haven't been done, she noted.

Bextra, also made by Pfizer, is the only other cox-2 left on the market. (Health Canada classes meloxicam, sold under the brand name Mobicox, as a cox-2 drug, but other jurisdictions do not and experts argue it is not a classic cox-2.)

Studies have shown that Bextra raises heart-attack risks in patients who've recently undergone coronary bypass surgery.

On Friday, the New England Journal of Medicine released a letter from three researchers from Valderbilt University School of Medicine in Nashville, Tenn., calling for a moratorium on Bextra's use in the interest of public safety.

Source: Canadian Press

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