The Food and Drug Administration (FDA) in the United States has warned doctors about the dangers of a drug used to treat pain in cancer sufferers.
The FDA says the drug Fentora carries a risk of a potentially fatal overdose.
Fentora is approved for use with cancer patients whose pain cannot be adequately controlled by conventional powerful painkillers such as morphine.
The drug is produced by Cephalon and comes in pill form and the warning follows several patient deaths related to inappropriate prescribing of the drug.
The FDA says it is crucial that doctors precisely follow prescribing instructions in order to avoid fatal overdoses of the drug and it should not be used for short-term management of migraines or headaches.
Steven Galson, the head of the FDA's center for Drug Evaluation and Research, says the FDA is monitoring the issue very closely but health care professionals and patients need to be aware of the potential for fatal overdose with the improper use of Fentora.
Currently doctors can prescribe drugs for uses outside their approved labeling, a practice known as off label use, and Cephalon has applied for FDA approval for the use of Fentora with a broader group of pain patients.
An inquiry in 2006 by the Connecticut attorney general found that Cephalon had promoted some drugs for uses for which they were not approved, which is illegal.
Earlier this month Cephalon released details of three deaths of patients taking Fentora which were due to improper patient selection, dosing or product substitution as well as using the drug in patients who cannot tolerate opioids; one of the deaths was a suicide.