The wave of bad news for drug companies that began last year when Merck & Co. Inc., pulled its blockbuster drug Vioxx from the market continued yesterday when Pfizer Inc. announced it would withdraw the anti-arthritis medicine Bextra amid concerns it, too, increased the risk of heart attacks.

The federal Food and Drug Administration asked the company to remove Bextra from the market but told Pfizer it could continue to sell Celebrex, a more popular medicine in the same class of painkillers. Celebrex must now carry the strongest warning FDA can mandate -- a so-called black box warning -- but the labeling requirement also applies to other prescription drugs sold in the class, the agency announced.

FDA officials, who also announced changes in the labels for some over-the-counter painkillers, urged calm among patients.

"What we're asking [for] is that the labeling make it more explicit, but none of these risks are new," said Dr. Steven K. Galson, acting director of FDA's Center for Drug Evaluation and Research.

Vioxx, Bextra and Celebrex are all non-steroidal anti-inflammatory drugs that work by inhibiting the cox-2 enzyme, which is involved with pain and inflammation. The drugs have been popular because they offer pain relief without the stomach problems caused by older arthritis medicines.

Merck withdrew Vioxx after studies showed increased risks of cardiovascular problems among patients taking the drug. In December, FDA upgraded warning labels on Bextra to reflect the increased risk of both heart problems and serious skin reactions.

The combination of those risk factors, set against the lack of compensating benefits, led FDA to call for Bextra's removal, said Dr. John Jenkins, director of the FDA's office of new drugs.

Pfizer said in a statement the company "respectfully disagrees" with FDA's position but would suspend sales pending further discussions.

Financial analysts said the news could have been worse for Pfizer, which saw its stock price fully recover yesterday after an initial drop of about 3 percent.

A slim majority of members on two FDA advisory committees who deliberated over the fate of Bextra in February voted to keep the drug on the market. But Galson said yesterday the decision to call on Pfizer to pull the drug was in keeping with the divided nature of the advisory committees' vote.

"With Bextra, it doesn't surprise me," commented Dr. Kelly Krohn, director of clinical research at Mercy Hospital, who said there was only limited information about the drug's cardiovascular safety.

Krohn downplayed the clinical significance of the cox-2 inhibitors. "These are glorified Advils that were grossly over-marketed and overpriced," he said.

But many patients relied on the drugs. Cox-2 inhibitors have been hugely important to shareholders of Pfizer and Merck. Yesterday's news was clearly mixed for investors, but there were encouraging words, said Robert Hazlett, who follows pharmaceutical companies for SunTrust Robinson Humphrey.

The fact that Celebrex will carry the same black box as older non-steroidal anti-inflammatory drugs sold in prescription strength means the Pfizer drug actually could bounce back a bit in sales, Hazlett said. Pfizer might never again see a year like 2004, when it sold $3.3 billion worth of Celebrex; Hazlett yesterday upped his Celebrex sales estimate for 2007 to $1.85 billion.

Pfizer sold more than $1 billion worth of Bextra during 2004, Hazlett said, but it was clearly the least popular of the three cox-2 inhibitors. Locally, Highmark Blue Cross Blue Shield did not include Bextra on its formulary of drugs for which it provides the highest level of coverage.

Hazlett said FDA's decision yesterday left open the chance for Merck to bring Vioxx back on the market -- another encouraging sign for investors. A slim majority of advisory committees that met in February supported a return for Vioxx.

But Randy Juhl, the former dean of the University of Pittsburgh's pharmacy school and a vice chancellor at Pitt, saw things differently.

"If Merck held any hopes of getting Vioxx back on the market, I don't think that was reinforced by today's announcement," he said. "If the agency had asked Pfizer just to temporarily suspend sales and marketing, I would have taken that as a positive thing for Vioxx."

Pfizer closed Thursday up four cents to $26.90. Merck was up 60 cents to 33.49.