Pfizer finds heart risk with Celebrex drug

CTV.ca News Staff
December 18, 2004 9:23 AM ET

Patients who were recently warned off arthritis drug Vioxx are facing uncertainty after new findings that Celebrex, the alternative, puts them at increased risk of heart problems.

Pfizer Inc. announced the news Friday. And despite a plummeting stock and an alarmed public, the company had no immediate plans to pull the drug off the market.

"A lot of people rely on these drugs believing they are safer ... now that trust has been broken and there is a lot of uncertainty," said Dr. Muhammad Mamdani, doctor of pharmacy and a senior scientist at Toronto's Institute for Clinical Evaluative Sciences.

But he added that other trials have not had these findings.

"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.

Pfizer said one of two long-term cancer prevention trials had found that patients taking Celebrex daily had a 2.5-time increased risk of experiencing cardiovascular problem compared to those on the placebo.

The other trial, sponsored by Pfizer, found no increased risk to patients.

Pfizer is not pulling Celebrex from the market, but has said it will study the results of the trial by the National Cancer Institute, which has halted the experiment.

"Pfizer is taking immediate steps to fully understand the results and rapidly communicate new information to regulators, physicians and patients around the world," said Hank McKinnell, Pfizer chairman and chief executive officer.

Celebrex is approved for use in the United States for treatment of arthritis and pain, and is in the same class as the arthritis drug Vioxx.

Vioxx, made by Merck & Co., was pulled from the market Sept. 30 after a study indicated the pain reliever doubled the risk of heart attacks and stroke when taken for longer than 18 months.

Concerns about cox-2 inhibitors

Vioxx and Celebrex are in a class of pain drugs called cox-2 inhibitors. They are popular for their effectiveness in treating the pain of arthritis and other ailments.

"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 Dr. Garrett Fitzgerald, a cardiologist and pharmacologist who has been studying the drugs even before they went on the market.

Concerns have also been raised about another cox-2 inhibitor produced by Pfizer, called Bextra.

The New England Journal of Medicine rushed Friday to print a letter warning doctors not to prescribe Bextra -- also known as valdecoxib -- due to concerns about potential cardiovascular risks.

"We believe the doubts raised about the safety of valdecoxib constitute a potential imminent hazard to public health and thus require action," the letter says.

The label for Bextra was changed by Pfizer in November to include a warning for patients who have recently had bypass surgery. But the authors of the NEJM letter say such changes will have little effect.

"These changes to the label do not address concerns about the cardiovascular safety of the drug in the general population."

The letter was to be published in the NEJM on Dec. 23, but the authors released it early in light of the announcement today from Pfizer about Celebrex.

The U.S. Food and Drug Administration and Health Canada have both said they are studying all cox-2 drugs.

Health Canada advised patients taking daily doses of 400 mg or 800 mg "should discuss with their health professional whether the risk of cardiovascular side effects outweigh the benefits."

Pfizer's announcement sent the company's stock tumbling in early trading on the New York Stock Exchange.

There is at least one difference between the two studies. In the first study, conducted by the NCI, patients were taking the 400 mg and 800 mg dose. In the Pfizer study, patients were only taking the 400 mg dose.

The two studies for Celebrex involve about 3,600 patients over a five-year period. Pfizer estimates that about 2,400 patients evaluated in the cardiovascular analysis have completed two years of treatment.

The trials were being conducted to find a new application for the drug.

With files from CTV's Avis Favaro and Canadian Press