Pfizer: Celebrex Poses Heart Risk

Pfizer Inc. says it has found an increased risk of heart problems with patients taking its painkiller Celebrex, a drug that is in the same class as Vioxx, which was pulled from the market in September because of safety concerns.

Pfizer announced Friday that it found the increased risk in one of two long-term cancer prevention trials, while the other trial showed no increased risk. The company was conducting the trials as part of an effort to find a new application for the drug.

The National Cancer Institute, which was conducting the study for Pfizer, suspended the use of Celebrex after finding that patients taking 400mg to 800mg of the drug daily were found to have a risk of 2.5 times greater of experiencing heart problems than those who weren't. A separate cancer study found no increased heart risk with patients taking 400mg of Celebrex per day.

"I think many doctors have already 'triaged,' if you will, their patients who are on it, deciding who's appropriate to stay on it and who's not appropriate to stay on it," CBS News Health Correspondent Dr. Emily Senay said.

The news sent the stock of the giant pharmaceutical maker plunging in early trading on the New York Stock Exchange.

Pfizer said it has no plans to pull the drug from the market. Celebrex is currently approved for use in the United States for the treatment of arthritis and pain.

"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, in a statement.

"I think the reason they're releasing this information is they want to be perceived as having full disclosure, not withholding anything," said Senay. "They want doctors to have this information, and this information, even though it's conflicting, is helpful for doctors."

Earlier this month, the Food and Drug Administration said it was adding a warning to the labels of another Pfizer drug, Bextra, warning of potential heart problems associated with the use of that drug in people who have recently had heart bypass surgery.

"We know that this happens in some people, it's real," said Senay. "It's always a problem when the you need to weigh the risk versus the benefit, and that's what this question is about."

Bextra, Celebrex and Vioxx are all in a class of pain drugs called cox-2 inhibitors. The drugs have become popular because of their effectiveness in treating the pain of arthritis and other ailments.

A study released earlier this month suggested that the top-selling pain reliever does not carry the same heart attack risk as Vioxx, a similar drug pulled from the market in September because of safety concerns.

The study by researchers at the University of Pennsylvania was the first to compare the two arthritis drugs since the recall, and contradicts claims by other scientists that all so-called cox-2 inhibitors may carry similar dangers.

"Vioxx and Celebrex look different. Relative to Celebrex, Vioxx had about a threefold greater risk of heart attacks," said Dr. Stephen Kimmel, associate professor of medicine and epidemiology and lead author of the study. "What that implies is that all cox-2 inhibitors may not be the same."

The chances of having a heart attack were 2.72 times greater in Vioxx users than in Celebrex users, the researchers said.

But the researchers also found that patients using either drug were not at a significantly greater risk of having a heart attack than those who did not use either drug. In fact, Celebrex users had a lower risk of a heart attack than people who didn't take either drug, though the researchers said that finding could have happened by chance.

In an accompanying editorial, two Boston doctors warned that the connection between heart disease and cox-2 inhibitors remains unclear. As a result, they recommended that doctors avoid prescribing any drug in that class to patients already in danger of heart disease, unless they run a significant risk of gastrointestinal problems. Cox-2 inhibitors are believed to be easier on the stomach than other pain relievers.

"We don't think that we really understand what is triggering the increased risk of heart problems in some patients," said Dr. Axel Finckh, rheumatology researcher at Brigham and Women's Hospital. "We cannot exclude the possibility that there is a cox-2 class effect."

"Vioxx had a study that clearly showed double the risk of cardiovascular events. Now, it looks like Celebrex also has a study that shows two-and-a-half times the risk of cardiovascular events in one particular study, and then no risk in another study," said Senay.

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

In October, sales of the Pfizer Inc. drug Celebrex topped $260 million, or 63.5 percent of the market for cox-2 inhibitors, according to IMS Health data.