Similar Medicines, Different Message

DRUG SAFETY

Following Merck's withdrawal of Vioxx, Pfizer has issued contrasting statements on its COX-2 inhibitors: Bextra and Celebrex.

According to Pfizer, Bextra (valdecoxib), which was approved in 2001, is associated with an increase in cardiovascular events, such as heart attacks and strokes, in patients who have been administered the drug after coronary artery bypass graft surgery.

A review of clinical trials with patients who have taken Bextra for arthritis for less than a year, on the other hand, shows no increased risk of cardiovascular events, the company says. Studies on the long-term safety of Bextra for arthritis patients are planned by Pfizer.

In the case of Celebrex (celecoxib), which was approved in 1998, Pfizer says it will sponsor a large study to assess whether the drug actually has cardiovascular benefits.

Can different COX-2 inhibitors carry different risks for patients with heart disease? "I don't know if anyone can answer that question right now," says Woodrow Corey, a cardiologist at Indiana Heart Hospital.

Vioxx, Bextra, and Celebrex are in the same drug family, but they all have different chemical makeups, Corey notes. "It is very difficult to make that jump and say 'Just because they are similar, the risk is the same,' " he says. Some studies show that Celebrex might be beneficial and not have the risks that Vioxx revealed in early trials, he says.

Pfizer's new Celebrex trial will probably require special review given the results with other COX-2 inhibitors, says Tony Butler, a pharmaceutical industry analyst at Lehman Brothers. In his view, the Pfizer and Merck announcements must be viewed separately. "We have to be very careful how we think about this as opposed to knee-jerk reactions to what we don't know," Butler says.