Makers of the popular pain killer Celebrex, the arch rival of Vioxx, which was pulled off the market this fall, have been asked by Canadian health authorities for further proof Celebrex is safe.
The request follows reports from health-care professionals about adverse reactions; 20 patients have died in recent years while taking Celebrex. It remains unclear, however, what role, if any, the drug actually played in their deaths.
In one case, for example, the patient suffered a "bleeding event," but was also taking an anti-blood-clotting drug, said Maria Valois, director of marketed pharmaceuticals for Health Canada.
"[This number] does not imply causality at all," Ms. Valois said in a teleconference yesterday, explaining there are "too many confounding factors" to determine the significance of the reports. But six of the 20 cases, she said, have raised questions about the drug's side effects. As a result, Ms. Valois said, in mid-October Health Canada asked Pfizer Inc., the makers of Celebrex, to submit further information about the drug's safety within 30 days.
Michael Amos, a spokesperson for Pfizer Canada, confirmed last night that safety data was sent yesterday to Health Canada. While he could not offer details on exactly what information "the package" included, he stressed that the drug has been found safe in studies involving more than 30,000 patients.
There is suspicion, however, among some doctors and patients that this new class of popular painkilling drugs known as cox-2 inhibitors (short for cyclo-oxygenase-2 inhibitors), which shuts off the cox-2 enzyme involved in pain and swelling, may be bad for the heart.
Vioxx, which hit the market in 1999, was withdrawn by its manufacturer, Merck & Co., in September after a clinical trial found it increased the risk of heart attack and stroke.
Ms. Valois noted yesterday that Health Canada asked Pfizer in 2002 to include on its label that Celebrex may increase the risk of congestive heart failure. But Mr. Amos said that risk applies to people with existing heart conditions.
Ms. Valois refused to answer repeated questions yesterday as to whether she would recommend Celebrex as "safe," saying that all drugs on the market have risks and benefits.
Meanwhile, a new study in The Lancet medical journal concludes that there was enough evidence several years ago to justify the removal of Vioxx from the pharmaceutical market.
Researchers led by Peter Jüni of the University of Berne in Switzerland pooled the results of numerous trials involving Vioxx to establish whether the drug's potential problems were apparent.
They found that by the end of 2000, 52 out of about 20,000 patients in those studies had had a heart attack. This equates to more than a doubling of the risk in patients given Vioxx, compared to those who received placebos or other drugs.