A powerful painkiller for cancer patients that lead to the death of four persons, apparently through misuse, has led manufacturer Cephalon Inc. and the FDA to issue a warning.

Manufacturer Cephalon Inc. said Thursday that all four deaths apparently involved the misuse of the potent drug.

Fentora was approved by the Food and Drug Administration in September 2006 only for cancer patients already taking morphine or other prescription narcotics for their pain.

Fentora contains fentanyl, an analgesic far more powerful than morphine, reports the Associated Press.

The FDA said it was monitoring the current situation closely.

Two of the victims were patients prescribed Fentora for headaches. Another death involved a suicide, while the fourth was a patient administered the drug outside the recommended dosing.

“None of the reports were in cancer patients, which leads us to believe they were inappropriate candidates for the product,” Cephalon spokeswoman Candace Steele said.

Steele said the deaths were not related to allegations that Cephalon had conducted an improper promotion of Fentora for other uses than those appearing on the FDA-approved label.

The deaths occurred over the summer. Cephalon reminded doctors and pharmacists of the potential danger of Fentora if not used as indicated. The company also warned not to substitute Fentora on a one-for-one basis for another drug, an older fentanyl product called Actiq, also produced by Cephalon, which is considerably weaker than Fentora.

A safety alert posted on the FDA’s official website by Cephalon (http://www.fda.gov/medwatch/safety/2007/safety07.htm#Fentora) says the deaths occurred as a result of improper patient selection (patients with an intolerance to painkillers), improper dosing, and/or improper product substitution.