New York, April 7 (Reuters): Pfizer Inc. today suspended sales of its arthritis drug Bextra on requests by US and European regulators, who said the risks of potentially fatal side effects outweigh the benefits.

The US Food and Drug Administration also asked Pfizer to include a black box warning ? the strongest possible ? for its painkiller Celebrex. Bextra and Celebrex are part of a class of drugs known as COX-2 inhibitors that also includes Merck & Co?s Vioxx, which was withdrawn last year due to increased risks of strokes and heart attacks.

The FDA said it singled out Bextra for suspension because it gives no added advantage as a painkiller and can cause a potentially life-threatening skin condition called Stevens-Johnson syndrome, an allergic reaction that usually begins as a blistering of the mouth and lips and can spread to the rest of the body.

The agency also asked the makers of dozens of other prescription and non-prescription painkillers, including Motrin, Advil and Aleve, to strengthen warnings about heart risks and potentially life-threatening gastrointestinal bleeding. The new warnings do not apply to aspirin.

Motrin and Aleve are members of a class of drugs known as non-steroidal anti-inflammatory drugs, or NSAIDs. Bextra, Celebrex and Vioxx are selective NSAIDs designed to reduce the risk of gastrointestinal bleeding.

Pfizer said it disagrees with the regulatory decision on Bextra and will explore options with the FDA under which it might be allowed to resume sales of the drug.

The FDA?s decision is the latest in a long series of actions by companies, regulators, advisors, lawyers and consumers that began last September when Merck withdrew Vioxx after a clinical trial showed it doubled the risk of heart attack and stroke in patients who took it for more than 18 months.

The FDA in December had called on doctors to limit prescribing Celebrex and Bextra in light of evidence that they also may increase the risk of heart attack and stroke. The FDA said it is now willing to ?carefully review? any proposal by Merck to reintroduce Vioxx.

An advisory panel to the FDA in February had concluded that Vioxx, Bextra and Celebrex all posed some level of heart risk, but said that Vioxx was safe enough to return to the US market and that all three drugs should carry black box warnings.