Pfizer’s top-selling painkillers, Celebrex (celecoxib) and Bextra (valdecoxib), should be subject to any revised approval standards the US Food and Drug Administration applies to the newer drugs in the COX-2 inhibitor class as part of its review into the products’ safety, including possible additional safety trials, an advisory committee member said yesterday.

Garret FitzGerald, who presented the cardiovascular safety of the product class on the first day of the three-day meeting that was prompted by Merck & Co’s withdrawal of Vioxx (rofecoxib) [[01/10/04a]], and subsequent safety concerns about other such medicines [[20/12/04a]], [[25/01/05b]], said that any new approval standards developed to address the cardiovascular safety of COX-2 inhibitors still in development should be extended to marketed drugs “as a condition of their retention of approval.” He added: “We’re likely to subject new drugs that might be approved from this class to significant hurdles before they’re approved. It seems logical to me that existing drugs in this class should be subject to the same hurdles for retention of approval, particularly for extended dosing.”

Pfizer reportedly reiterated its arguments that the cardiovascular risk seen with Vioxx is specific to that drug and its mechanism of action and not to the class as a whole. However, this was challenged by Dr Fitzgerald, who said: “There are a lot of off-target fantasies being touted around at the moment: strange chemical interactions that haven’t actually been shown to occur in vivo yet, but are postulated as the explanation for a drug-related rather than a class-based effect.”

Until studies are conducted to determine how COX-2 inhibitors can be more safely administered, Dr FitzGerald recommended the agency restrict the use of marketed products to patients not at increased risk for cardiovascular events. However, he acknowledged that such a recommendation would be tricky to implement.