Pfizer Inc.‘s painkiller Bextra will come with a new warning about the possibility of heart attacks and blood clots in patients who have just had heart bypass surgery, the U.S. Food and Drug Administration said on Thursday.

The FDA said it still considers the drug beneficial when taken for approved uses, such as relieving arthritis pain.

“FDA believes that, based on what we know now, the overall benefit of Bextra outweighs the risk when used in properly selected patients as directed in the approved labeling,” the FDA said in a statement posted on its Web site.

A Pfizer study of more than 1,500 patients who had just had heart bypass surgery found that patients treated with Bextra for pain were more likely to have heart attacks, strokes and blood clots in the legs or lungs than others who took a placebo, the agency said.

Bextra is not approved for treating pain following heart bypass surgery. The new warning specifically urges doctors not to use the drug in that setting.

The updated Bextra label also includes a stronger warning, now highlighted in a black box, about the possibility of a rare, potentially fatal skin reaction known as Stevens-Johnson Syndrome. As of November, the FDA had received 87 reports of that condition and other skin reactions. Thirty-six of the patients were hospitalized and four died, the FDA said.

Bextra is getting close attention from regulators because it is in the same family of drugs as Merck & Co. Inc.‘s arthritis pill Vioxx, which was pulled from the market Sept. 30 after a study showed the drug doubled the chances of heart attacks and strokes when used for more than 18 months. Both drugs are so-called COX-2 inhibitors.

Bextra, which was launched in 2001, had sales last year of $687 million.

Pfizer spokeswoman Mariann Caprino said the company had no comment on the heart warning. “There’s no new information in the label. It’s all been previously shared with the medical community,” she said.

Pfizer announced in October that two small clinical trials of Bextra showed heart bypass patients had an increased risk of stroke and heart attack. The company also said at the time it was adding the skin-related warning to the drug’s packaging.

The FDA is planning a public advisory committee meeting in February to discuss safety concerns with Bextra and other COX-2 inhibitors, including another Pfizer painkiller, Celebrex.

Pfizer shares fell 28 cents, or 1.02 percent, to close on Friday at $27.09 on the New York Stock Exchange.