Cephalon ( CEPH) reported encouraging results from a clinical trial designed to determine if the cancer-pain drug Fentora could be used for broader indications. As a result, the Frazer, Pa.-based drugmaker expects to seek regulatory approval during the third quarter for Fentora to treat jolts of intense discomfort, referred to as breakthrough pain, in people with chronic nerve pain. This nerve condition, called neuropathic pain, can have a variety of causes, including diabetes, multiple sclerosis and alcoholism. In late September, the Food and Drug Administration approved Fentora for treating breakthrough pain, which the company says can last from three minutes to 60 minutes, in cancer patients who are taking and can tolerate strong narcotic painkillers. Fentora, a tablet that dissolves in the mouth, carries a "black box" warning, the FDA's strongest safety alert, about the potential for abuse. The drug contains the narcotic fentanyl, and it has the same abuse warning as methadone and morphine. The market potential for treatments other than for cancer pain is "quite large," Stacey Beckhardt, a Cephalon spokeswoman, said Monday. The company estimates that the cancer-pain market includes 800,000 people. Cephalon says the number of people with moderate to severe chronic pain conditions, such as neuropathic pain or back pain, could be 2 million to 3 million. Among noncancer patients with chronic pain, 74% will experience breakthrough pain, according to research published in the August edition of The Journal of Pain. The research, funded by Cephalon, was lead by Dr. Russell Portenoy, chairman of the department of pain medicine and palliative care at the Beth Israel Medical Center in New York. Portenoy has been a clinical investigator for tests of Fentora.