The U.S. Food and Drug Administration rejected Merck & Co.'s request to market a successor to its withdrawn arthritis drug Vioxx in the United States, the drug maker said Friday.

The move was widely expected, after a panel of FDA advisers two weeks ago voted 20-1 against approving the drug, Arcoxia.

Arcoxia is in the class of anti-inflammatory drugs called COX-2 inhibitors, which are touted as less likely to cause stomach bleeding and other dangers but have been linked to cardiac risks.

It is in the same class of drugs as Vioxx, which has become a poster child for drug safety problems.

Merck pulled Vioxx from the market in September 2004 after research showed it doubled risk of heart attacks and strokes. That triggered an avalanche of lawsuits, more than 27,000 so far, and a nosedive for Merck's stock price, which has since bounced back.

Despite the safety concerns in the United States, Arcoxia is on sale in 63 other countries not including Canada, and Merck officials said as recently as Tuesday that they intended to keep working to get it on the U.S. market.

Merck spokesman Ron Rogers said the company would not discuss whether it now will drop efforts to get Arcoxia approved in the U.S., saying the company's strategy is proprietary information.

Analyst Steve Brozak of WBB Securities said he believed Merck officials were "just going through the motions" with the FDA approval on Arcoxia. "This is it. Put a fork in it and it's done," he said.

Safety data questioned

Arcoxia had been poised for approval until Vioxx was pulled from the market. Two months later, the FDA issued an "approvable" letter, saying it could approve Arcoxia, but only if Merck provided further safety and efficacy information for the drug.

Merck has since produced results from further studies of Arcoxia, but doctors questioned those results because Merck compared Arcoxia in its tests to another, older anti-inflammatory drug, diclofenac — widely used elsewhere, but not in the U.S. — that has elevated risk of heart attacks and strokes. Merck said the two drugs have similar cardiovascular risk.

However, Arcoxia causes high blood pressure in more patients than diclofenac.

Peter S. Kim, president of Merck Research Laboratories, told company shareholders at their annual meeting Tuesday that "there is more long-term safety data on Arcoxia than" other drugs in the same class and traditional anti-inflammatory medicines.

In the statement issued Friday, Kim said the company is disappointed by the decision.

"We pursued FDA approval of Arcoxia because we believe strongly that new medicines are needed for patients whose osteoarthritis pain is inadequately managed with currently available therapies," he said.

Brozak said the market for arthritis drugs clearly is growing, but that he thinks the FDA and the medical community are tired of drugs that "just retool" existing ones.

Merck shares sank 76 cents, or 1.5 per cent, to $51.67 in Friday morning trading on the New York Stock Exchange, still near their 52-week high of $52.63. Their low over the past year was $32.75.