Right now, the COX-2 inhibitor drug market is riddled with uncertainty and in desperate need of pain relief.

Merck's ( MRK) Vioxx is gone. Its presumed successor, Arcoxia, is sold in 47 countries but not in the U.S.; and Merck is talking to foreign regulators about the drug following the U.S. Vioxx withdrawal.

In late October, the Food and Drug Administration granted conditional approval for Arcoxia, but that approval includes more clinical testing to assess long-term safety and efficacy. Merck has declined to provide details on what it would have to do and how long it would take. Clearly, Arcoxia won't reach the U.S. market for at least several years, and many analysts have dropped any prediction of U.S. sales for many years in their economic models.

As for Pfizer ( PFE), it recently added several warnings to the Bextra label. (For a brief history of Bextra and Celebrex click here.)

Since 2002, a year after Bextra reached the U.S. market, the drug's label has carried a warning about Stevens-Johnson syndrome, a rare and sometimes fatal skin reaction. Recently, Pfizer, after discussions with the FDA, paid notice to this dangerous side-effect with a black box warning, the strictest alert required by the FDA.

Pfizer also added a warning to the label reflecting a recent study that showed the drug poses a higher risk of cardiovascular problems for patients undergoing heart bypass surgery. The risk was detected among patients who took Bextra and another Pfizer COX-2 drug that is not available in the U.S.

Some of the these problems cited by the FDA include heart attack, stroke, blood clots in the legs and blood clots in the lungs.

Another study of heart bypass patients taking only Bextra revealed a higher cardiovascular risk that wasn't considered statistically significant compared to patients taking a placebo. In addition, Pfizer says a third study of patients undergoing general surgery found no significant risk of cardiovascular problems among those receiving Bextra and the other COX-2 drug.

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