Washington ? The blockbuster painkiller Bextra was yanked off the market Thursday, and the government ordered 19 other popular prescription competitors — from Celebrex to Mobic to high-dose naproxen — to carry tough new warnings that they, too, may increase the risk of heart attacks and strokes.

The warnings encompass an entire class of anti-inflammatory medicines called NSAIDs that are the backbone of U.S. pain treatment, not just newer versions of the painkillers initially suspected when the heart concerns made headlines last fall.

The warnings — in black boxes, the strongest the Food and Drug Administration can order — are likely to cause confusion because they won’t tell patients and doctors which of these prescription drugs is a safer choice.

In addition, the FDA will make over-the-counter NSAIDs — or nonsteroidal anti-inflammatory drugs, such as ibuprofen, naproxen and ketoprofen — bear stronger reminders to take only low doses for a few days at a time to avoid the same risks of high-dose, long-term use.

Worried patients immediately began calling doctors and pain groups to ask what drug they should take. The FDA advised patients to ask which painkiller is best suited to their personal health risks, and then take the lowest dose possible.

There simply isn’t enough research yet to rank which drug will pose fewer heart problems, said FDA drug chief Dr. Steven Galson. “A lot of the data conflicts,” he said.

The FDA is asking painkiller manufacturers to sift through their research to help figure that out.

“Let me emphasize now, this announcement is unlikely to be the last word you’ll hear on these drugs,” Galson said.

The saga began in September when Merck & Co. voluntarily pulled its pain reliever Vioxx off the market after a study showed long-term use doubled patients’ risk of heart attacks and strokes. Pfizer Inc.’s Bextra and Celebrex are similar drugs, a subset of NSAIDs known as cox-2 inhibitors, and studies show they also can raise cardiovascular risks, although apparently to a smaller degree than Vioxx.

Pfizer reluctantly suspended Bextra sales in the United States and European Union on Thursday, at the request of the FDA and its European counterparts. In addition to the cardiac concern, the FDA said, Bextra appears to cause rare but serious skin conditions — some fatal — more often than do other NSAIDs, making the drug too risky to remain on the market.

Pfizer’s Celebrex still can sell, the FDA announced Thursday.

But it and all other prescription NSAIDs must carry a major warning on the label that long-term use may cause serious cardiovascular side effects or gastrointestinal bleeding. No one who recently underwent heart bypass surgery should use prescription-strength NSAIDs, the warning stresses.

Also, patients are to receive a special pamphlet with every NSAID prescription filled that spells out the warnings in consumer-friendly language.

Thursday’s move was a blow to Pfizer, which said it “respectfully disagrees” with the FDA that the drug, which had sales of $1.3 billion last year, is too risky. Pfizer pledged additional research on Bextra’s heart risks and said it would try to bring back the drug.