Philadelphia ? New research suggests that top-selling pain reliever Celebrex does not carry the same heart attack risk as Vioxx, a similar drug pulled from the market in September because of safety concerns.

The study by researchers at the University of Pennsylvania is the first to compare the two arthritis drugs since the recall, and contradicts claims by other scientists that all so-called cox-2 inhibitors may carry similar dangers.

“Vioxx and Celebrex look different. Relative to Celebrex, Vioxx had about a threefold greater risk of heart attacks,” said Dr. Stephen Kimmel, associate professor of medicine and epidemiology and lead study author. “What that implies is that all cox-2 inhibitors may not be the same.”

The study, funded by the makers of both drugs and the federal government, was published in today’s Annals of Internal Medicine. Researchers surveyed 1,718 Philadelphia- area patients who were treated for heart attacks at one of 36 hospitals, and a comparison group of 6,800 people in the region.

The chances of having a heart attack were 2.72 times greater in Vioxx users than in Celebrex users, the researchers said.

But the researchers also found that patients using either drug were not at a significantly greater risk of having a heart attack than those who did not use either drug. In fact, Celebrex users had a lower risk of a heart attack than people who didn’t take either drug, though the researchers said that finding could have happened by chance.

In an accompanying editorial, two doctors warned that the connection between heart disease and cox-2 inhibitors remains unclear.