US drug giant Pfizer said Friday a trial had found a sharp rise in heart attacks for patients using its blockbuster Celebrex arthritis and pain medicine but it would not immediately withdraw the treatment.
The US Food and Drug Administration said that action could be taken over the findings of one new cancer study, which led to an immediate halt in dosing of Celebrex in the trial. A second new study did not find an increased risk.
Celebrex is used by 26 million people, according to Pfizer, and is the latest COX-2 type pain drug to face controversy. Vioxx, made by the rival Merck and Co., was withdrawn in September because of the increased risk of heart attacks.
Three US doctors on Friday appealed for physicians to stop prescribing Bextra, another COX-2 painkiller, also made by Pfizer.
News of the Celebrex study sent Pfizer shares slumping but the US firm's chairman Hank McKinnell said the drug would not be withdrawn.
"Any decision to withdraw a drug has to be made in the context of all of the information," McKinnell told CNBC television.
"Until the study results became known to us late last night we saw a very acceptable safety profile for Celebrex."
"I don't think this one study, even though it is a large, well-controlled study, characterizes the drug in any significant way," McKinnell said.
A study into the use of Celebrex to prevent benign tumours, or adenomas, showed patients taking 400mg and 800mg of Celebrex daily had an approximately 2.5-fold increased risk of major cardiovascular problem compared to patients on a placebo, according to the National Cancer Institute.
Based on the "statistically significant" findings, the institute, which sponsored the trial, suspended the dosing of Celebrex. The news was given to Pfizer late Thursday.
A separate study into whether Celebrex can prevent polyps showed no increased risk to the heart.
Pfizer gave the results of the study straight to the US Food and Drug Administration and European regulators as soon as they were received, the company chief said.
In a statement earlier, McKinnell said: "These clinical trial results are new. The cardiovascular findings in one of the studies are unexpected and not consistent with the reported findings in the second study."
He added that "Pfizer is taking immediate steps to fully understand the results and rapidly communicate new information to regulators, physicians and patients around the world."
Merck announced a global withdrawal of its painkiller Vioxx on September 30, prompted by a study showing an increased risk of strokes and heart attacks.
Merck's share price has crumbled and it is now engulfed in lawsuits.
Pfizer shares plunged 3.23 dollars, 11.15 percent, to close at 25.75 dollars, wiping out 24.3 billion dollars in Pfizer market capitalization.
The drug earned 2.29 billion dollars in the first nine months of 2004 for Pfizer, against 1.07 billion dollars for the same period last year.
Celebrex is approved in the United States for the treatment of arthritis and pain at recommended doses of 100mg to 200mg daily for osteoarthritis and 200mg to 400mg a day for rheumatoid arthritis.
John Jenkins, a senior official with the US pharmaceutical regulatory body, indicated that the FDA could take action before an agency meeting in February.
He told a press conference that all information about COX-2 drugs would be reviewed. "We are not necessarily waiting until the February advsory meeting to consider what reglementary action is warranted," Jenkins said.