By Susan Heavey

GAITHERSBURG, Md. (Reuters) - U.S. health officials should not authorize expanded use of Cephalon Inc's (CEPH.O: Quote, Profile, Research) Fentora pain drug beyond cancer patients because of the potential for abuse of the powerful narcotic, a panel of outside experts said on Tuesday.

Panel members told the U.S. Food and Drug Administration that the opioid painkiller was already being misused, and recommend against approval in a 17-3 vote.

"Do we really want to flood the United States with this amount of product that is as potent as it is," questioned Timothy Lesar, pharmacy director for Albany Medical Center in New York, who voted against the company's bid.

Cephalon wants U.S. approval to sell Fentora to people without cancer who have sudden flare-ups of chronic pain and are already taking around-the-clock opioid medications. Currently, the tablets are only approved to treat such pain in cancer patients.

But since U.S. doctors are allowed to prescribe medicines as they see fit, nearly 80 percent of Fentora's yearly prescriptions -- or 70,000 to 80,000 -- are already given to patients without cancer, according to Cephalon.

Formal U.S. approval of such sales would allow the drugmaker to increase marketing efforts and pave the way for more health insurers to pay for it.

The drug, like other opioids, is highly sought after for its calming effects and can be easily abused.

Cephalon, which also sells a lollipop-like fentanyl product called Actiq, told the panel it had drastically revised its plan to help prevent misuse. It would set up a special registry so only participating patients, doctors and pharmacists could have access to the drug, among other efforts.