NEW YORK (CNN/Money) -
Pfizer Inc. said Friday it had no plans to pull the popular painkiller Celebrex off the market despite data showing that patients using the drug in a long-term cancer study had more than double the risk of a heart attack.
"We need to fully understand the information that we got last night" when the company learned of the study's findings, Pfizer spokesman Paul Fitzhenry said, adding it has "no plans to take Celebrex off the market."
The new findings for Celebrex come 11 weeks after Merck & Co. recalled Vioxx, a similar arthritis drug. A Vioxx study found the drug doubled the incidence of heart attack and stroke among patients taking it to prevent colon polyps that cause cancer.
The news sent the stock of Pfizer (down $3.23 to $25.75, Research) tumbling on the New York Stock Exchange.
Celebrex is approved in the United States for treatment of arthritis and pain at doses of 100 milligrams to 200 milligrams a day, or double that for rheumatoid arthritis.
Patients in the cancer study were taking 400 milligrams to 800 milligrams of Celebrex daily. The National Cancer Institute suspended the trial because the people on Celebrex showed greater cardiovascular risk than those taking a placebo.
A second cancer study found no problems with the drug, Pfizer said.
At least three times since Merck recalled Vioxx, Pfizer issued statements affirming the safety of Celebrex.
But Pfizer CEO Hank McKinnell said the results from the latest clinical trials were "unexpected," adding the company was taking "immediate steps to fully understand the results and rapidly communicate new information to regulators, physicians and patients around the world."
"These clinical trial results are new," McKinnell said in a news release.
Medical experts advised patients to consult their doctors about Celebrex.
"It's premature. We don't know how serious this risk is," Dr. John Abramson, a Harvard University medical professor and drug industry critic, told CNN Live Today when asked whether the drug should be withdrawn. "But patients need to know that giving up Celebrex does not mean they are giving up the best drug."
He said patients should not stop taking Celebrex until they're advised to do so by their doctor.
Industry analysts said the development was a blow to Pfizer, the world's largest drugmaker and one widely admired on Wall Street for its drug development and marketing.
"It's definitely not positive," said Sena Lund, an analyst for Cathay Financial in New York. "It has some of the same elements as (Merck's Vioxx)," he added, noting it was unclear what impact the news would have on Celebrex prescriptions. "The product will still be tainted," he said.
Lund had estimated before Friday's announcement that Celebrex would generate about $5 billion in sales for Pfizer next year, or about 9 percent of the company's total revenue.
Officials with the Food and Drug Administration and the National Institutes of Health are holding a news briefing later Friday about Celebrex, the FDA said in a statement.
In a related development, The U.S. House Energy and Commerce Committee said Friday it requested documents from Pfizer related to the painkillers Celebrex and Bextra.
The committee, in a letter to Pfizer CEO McKinnell, said it had concerns about Pfizer's statements in recent weeks about the safety of Celebrex.
Separately, New York-based Pfizer is facing an investigation by the New York's Attorney General's office related to Celebrex, a source familiar with the situation told CNN.
The source said the probe was not linked to Friday's announcement but rather focused on claims of the effectiveness of the drug. An official at New York Attorney General Eliot Spitzer's office declined to comment.
Celebrex, approved by the Food and Drug Administration in 1998 for arthritis pain, has been prescribed to 27 million Americans and is the world's most widely prescribed arthritis drug, according to Pfizer.
New York-based Pfizer said in October that Bextra, another painkiller similar to Vioxx, might raise heart attack risk in some patients having heart bypass surgery. And doctors wrote in a medical journal Friday that physicians should stop prescribing Bextra, which like Celebrex and Vioxx is in the COX-2 inhibitor class of painkillers. (For more on the New England Journal of Medicine article, click here).
On the same day Merck pulled Vioxx off the market, Pfizer said a recent FDA-sponsored study of 1.4 million patients showed Celebrex patients showed "no increased" cardiac risk. And on Nov. 4 and Nov. 30 Pfizer issued other statements vouching for the safety of Celebrex.
Celebrex and Bextra were developed by Pfizer's Pharmacia division, acquired in 2002. Analysts have projected worldwide sales this year of about $3.4 billion for Celebrex and $1.3 billion for Bextra.
When Merck pulled Vioxx on Sept. 30, its stock tumbled 27 percent, erasing $25 billion from its market value. Merck is facing hundreds of lawsuits and potentially billions of dollars in damages from Vioxx.
Pfizer stock sank as much as 24 percent early Friday, and was off about 12 percent in late trading.