USA-based drug giant Pfizer has received a non-approvable letter from the US Food and Drug Administration for its injectable COX-2 selective analgesic parecoxib sodium, which sold in other countries under the tradename Dynastat for the treatment of acute pain.

Although the firm would not divulge the exact nature of the FDA’s concerns over the drug, Pfizer said that it disagrees with its conclusions, and that it plans to meet with the agency in the near future to address its concerns.

Dynastat is already widely available across the globe, including in the European Union. Furthermore, as the only injectable COX-2 specific inhibitor, the drug provides physicians and patients with an important option in the treatment of acute pain in the post-surgical setting, says the company.

The news will certainly come as a blow to the world’s largest drugmaker, which had hoped that Dynastat, with potential peak sales in excess of $1 billion, would help claw back some of the losses felt by the withdrawal of Bextra this year [[08/04/05a]] - the agent generated sales of $1.3 billion in 2004 – and a rapidly declining income from its once top-selling Celebrex (celecoxib), which has suffered in the wake of the withdrawal of Merck & Co’s rival Vioxx (rofecoxib) [[01/10/04a]].

Earlier this year, Pfizer took the dramatic step of pulling its blockbuster Bextra (valdecoxib) from the market at the request of the US Food and Drug Administration, which said that the risks associated with Bextra’s use outweighed its benefits. This was followed by a similar ruling by the EMEA, which recommended the suspension of the drug [[28/06/05a]], but gave its backing to Dynastat after a thorough safety review of the entire COX-2 class of analgesics.

The European drug regulator concluded that, based on the overall safety data and with appropriate labeling, “the benefits (of Dynastat) continue to outweigh the risks,” Pfizer stated, adding that many other regulatory agencies worldwide conducted similar investigations and arrived at a similar conclusion.