By Susan Heavey

WASHINGTON (Reuters) - Approving Cephalon Inc's pain drug Fentora for patients without cancer could have "devastating effects," a U.S. Food and Drug Administration official said in documents released on Friday.

The company is seeking U.S. approval to market Fentora, the tablet formulation of a drug known generically as fentanyl -- a Schedule II controlled substance, as a treatment of sudden pain in non-cancer patients who have developed a tolerance to other opioid drugs. The drug is currently only approved in the United States for pain flare-ups in cancer patients who have developed a tolerance to other opioid drugs.

"We are concerned that the sponsor's request to expand the current indication for Fentora...may greatly increase the prescribing of this product which may increase the availability of the product for diversion, abuse and misuse," wrote Bob Rappaport, head of the FDA's Division of Anesthesia, Analgesia and Rheumatology Products.

Rappaport added that expanded use could also "increase the incidence of accidental exposures which, due to the potency of the product, could potentially have devastating effects."

Narcotic drugs, including opioids such as Fentora, are highly addictive and sought out for their calming effects. Even patients with pain can become dependent and abuse them.

Rappaport's comments were released ahead of an FDA advisory meeting on Tuesday to discuss the issue with a panel of outside experts. The agency is set to ask the panel whether wider use should be approved, according to the documents, although the FDA will make the final decision later.

Last September, the FDA issued a pubic warning over Fentora following reports that its use has led to deaths as well as breathing problems and other serious complications.

If the agency did allow Fentora to be marketed to non-cancer patients with chronic pain, Cephalon would have to have a plan in place to try to mitigate abuse, Rappaport said.

Cephalon, which also sells a fentanyl pain drug on a stick called Actiq, said the company has "extensive experience" in managing narcotic abuse, including its Fentora tablets.

Its efforts to oversee Fentora "were further developed and refined as surveillance data accumulated and safety signals were generated," it said in separate documents also released on Friday.

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