Pfizer Inc. said it has found an increased risk of heart attacks with patients taking its top-selling painkiller Celebrex, a drug that is in the same class as Vioxx, but has no plans to remove it from the market.
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 National Cancer Institute, which was conducting the study for Pfizer, suspended the use of Celebrex after discovering that patients taking 400mg to 800mg of the drug daily had a 2.5 times greater risk of experiencing major heart problems than those who were not. A separate cancer study found no increased heart risk with patients taking 400mg of Celebrex per day.
Pfizer was conducting the trials as part of an effort to find a new application for the drug.
The stock of the world’s largest pharmaceutical maker plunged in morning trading on the New York Stock Exchange, losing 14.6 percent, or $4.22, at $24.76 in heavy volume.
Both Celebrex and Vioxx, which is made by Merck & Co., are a type of drug called cox-2 inhibitors, which have become popular because of their effectiveness in treating the pain of arthritis and other ailments. Vioxx was pulled from the market in September because of safety concerns.
Dr. Marie Griffin, an epidemiologist and drug safety expert at Vanderbilt University, said the new findings on Celebrex is worrisome evidence suggesting that all these cox-2 drugs have similar risks.
However, she noted that the halted study was testing an 400 to 800 milligram dose – four times the usual dose – and that the safety problem with Celebrex may only apply to those high levels.
“What this means for people who have heart disease is it’s best to avoid these drugs,” she said.
For others, “people may want to reconsider their use of coxibs until we feel better about their safety,” and if they are using them, stick to the normal dose, Griffin said.
Dr. Richard Hayes, a cardiologist in New York, said he would be recommending that his patients taking Celebrex switch to nonprescription medicines such as Advil to treat their pain.
“We thought Celebrex was safe and the problem was just with Vioxx,” Hayes said. “The problem is more complex than we thought.”
Celebrex is the most-prescribed drug for treating arthritis. In the nine months ending in September, worldwide sales of Celebrex more than doubled from the same period a year earlier to $2.29 billion, accounting for 6 percent of Pfizer’s total sales of $37.59 billion.
In releasing news of the study’s findings, Pfizer chairman Henry McKinnell said in a statement the company wanted to “rapidly communicate new information to regulators, physicians and patients around the world.”
The withdrawal of Vioxx has been a financial and public relations disaster for Merck, in part because it has been accused of muzzling news about the drug’s side effects. Its legal liabilities are estimated at up to $18 billion, and its shares have dropped by nearly one-third since the recall announcement was made in late September.
Vioxx had been a blockbuster drug for Merck, it’s No. 2 earner with annual global sales of $2.5 billion, amounting to 11 percent of the company’s $22.49 billion in revenue last year. Some 2 million people worldwide had been taking Vioxx.
Dr. Joseph Feczko, president of worldwide development for Pfizer, noted that the results in the trial finding increased risk of heart attacks were not consistent with either the other cancer prevention trial or with a “large body of data” that the company had collected.
Earlier this month, the Food and Drug Administration said it was adding a warning to the labels of another Pfizer drug, Bextra, noting a risk of potential heart problems associated with the use of Bextra in people who have recently had heart bypass surgery. Bextra is also a cox-2 inhibitor type of drug.
Griffin and two other Vanderbilt epidemiologists also raised fresh concerns about Bextra, Pfizer’s other cox-2, in a letter to be published Thursday in the New England Journal of Medicine. Doctors should not prescribe the drug “except in extraordinary circumstances,” they recommend.
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