WASHINGTON (AP) -- Government regulators on Friday said encouraging wider use of a powerful painkiller made by Cephalon Inc. raises the risk of potentially fatal misuse of the drug.

Shares of the Frazer, Pa. drugmaker fell $2.7, or 4.2 percent, to $60.72 in morning trading.

Cephalon's drug Fentora is already approved to treat severe pain flare-ups in cancer patients. On Tuesday FDA will ask a panel of outside experts whether it should be approved to treat pain in non-cancer patients, a larger market that includes those suffering from back and nerve pain.

But FDA took a cautious tone in draft questions posted to its Web site Friday, stating that "Fentora has attributes that make it particularly attractive to abusers" and questioning whether broader approval would "lead to widespread abuse."

FDA is not required to follow the advice of its panelists, though it usually does.

The drug is currently used by about 20,000 patients, according to Cephalon. Fentora along with Actiq, an older version of the drug, accounted for 29 percent of Cephalon sales last year.

In its review of the new indication, FDA said granting wider approval could encourage "abuse and misuse, and increase the incidence of accidental exposures which ... could potentially have devastating effects."

FDA first approved the drug in 2006 with a strict indication for adults suffering from cancer pain who are already taking opioid drugs, a class of narcotics that includes morphine and codeine as well as Fentora.

But FDA said the drug has frequently been used outside those recommendations, resulting in negative side effects and death. Cephalon has reported five patient deaths due to improper use.

Prescription narcotics can quickly become addictive and are often abused for their euphoric effects.

Cephalon said in a statement Friday that there is "no evidence that Fentora poses risks of abuse and diversion greater than other opioids."

The company cited a study that showed medications like Fentora are no more appealing to heroin addicts than other types of narcotics.

Cephalon spokeswoman Stacey Beckhardt acknowledged Friday that many doctors already prescribe the drug off-label, or for uses not approved by FDA. She said the company felt a responsibility to expand the drug's FDA-approved indication to ensure it is used safely.

"Without that broader indication it is difficult for us to share important prescribing information with doctors, pharmacists and patients," Beckhardt said.

Despite the negative FDA review, Oppenheimer & Co. analyst Brett Holley maintained an "outperform" rating on the stock. Even without a larger Fentora franchise, Holley writes "the company has multiple revenue growth drivers beyond Fentora."

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