New trial results show that high doses of the arthritis drug Celebrex boost the risk of heart problems, the drug's manufacturer said Friday.

Pfizer Inc. said it noticed the problem while testing the anti-inflammatory drug as a long-term cancer prevention agent, using doses up to twice as high as those currently recommended for rheumatoid arthritis patients.

At those doses, cancer patients involved in the trial were 2.5 times more likely to experience a major heart attack than the patients who took a placebo, Pfizer said in a statement posted on its website.

Dr. Mohammed Mamdani
Dr. Mohammed Mamdani

Pfizer has no plans to pull Celebrex off the market.

The National Cancer Institute has suspended the use of Celebrex in the high-dose trials because of the new information.

A separate cancer study found no increased heart risk with patients taking 400 milligrams of Celebrex per day. Most arthritis patients take less than 400 milligrams daily.




Physicians need more information about the seemingly contradictory clinical trials before reaching any conclusions, said Dr. Mohammed Mamdani of the Institute for Clinical Evaluative Sciences in Toronto.

"The safest option really is, if you don't need the drug don't take them," Mamdani said. "If you can manage without, definitely do without. And if you do need them, use the lowest amount for the lowest time possible."

Scientists suspected inflammation may be one cause of cancer. The drug trials were designed to test the idea using Celebrex.

Latest COX-2 inhibitor concern

Celebrex is a COX-2 inhibitor, the same class of drugs as Vioxx and Bextra. That class of drugs had been hailed for treating arthritis and inflammation from other painful conditions.

Merck & Co. removed Vioxx from the market in September because of concerns it could double the risk of stroke and heart attacks if patients take it for longer than 18 months.

The COX-2 inhibitor drugs have been immensely popular with people suffering from arthritis, who had previously been taking powerful painkillers with unpleasant side-effects or relying on less effective drugs.

Prescriptions for Celebrex jumped more than 35 per cent, from about 250,000 in September to about 350,000 in October, after the Vioxx recall.

Officials at Health Canada said they have been talking to Pfizer about the drug and will continue to monitor its safety.

Late Friday, Health Canada told Pfizer it could no longer market Celebrex for the treatment of Familial Adenomatous Polyposis, a rare genetic disease.