By MARILYNN MARCHIONE

The Associated Press

CHICAGO -- The first published studies of Arcoxia, the drug that Merck & Co. hopes will take the place of its withdrawn painkiller Vioxx, are getting mixed reviews from doctors, some of whom say the results do not make a case for the medication's approval.

The critics cite not just Arcoxia's side effects but also that Merck tested it against diclofenac, an older painkiller known to raise heart risks. A fairer comparison would have been to a medicine that does not do that, such as naproxen, sold as Aleve, they say.

"The development program for Arcoxia is fatally flawed," said Dr. Steven Nissen, a Cleveland Clinic cardiologist who formerly headed the Food and Drug Administration's cardiac drug advisory panel. "My advice to the FDA is that they should not approve this drug."

Dr. David Graham, an FDA drug safety expert who has criticized his agency's handling of Vioxx, agreed.

"It's my own suspicion that this study was intentionally designed to minimize the possibility of their having a repeat of what happened with VIGOR," the study that revealed Vioxx's heart risks, he said.

The new research "raises red flags," Graham said, and gave his personal opinion that the drug should not be approved. "There's every reason to think it suffers from the same problems" as Vioxx, he said.

Vioxx was a blockbuster arthritis drug when Merck pulled it from the market in September 2004 over safety concerns. Like Arcoxia, it is a cox-2 inhibitor, a class of drugs originally developed to be gentler on the stomach and hopefully easier to take long-term than traditional pain relievers.

Arcoxia already is widely used in other countries, and Merck has been seeking approval to sell it in the United States. In August, the company said preliminary data from unpublished studies showed that Arcoxia did not increase heart risks more than diclofenac, sold as Cataflam and Voltaren by Switzerland-based Novartis AG.

On Monday, pooled results of three studies of Arcoxia were to be published in the British journal The Lancet and presented at an American Heart Association conference in Chicago.