Mallinckrodt's SpecGx division has announced the rejection of its abuse-deterrent re-formulation of opioid analgesic Roxicodone by the US Food and Drug Administration (FDA).

The FDA has issued a complete response letter rejecting approval of the abuse-deterrent, immediate-release reformulation of Roxicodone (oxycodone), the details of which have not been revealed.

The decision was unexpected, given that an FDA advisory panel recently recommended the drug in a 10-7 vote, although it did stress that it should only be labelled as abuse-deterrent if administered nasally.

Matt Harbaugh, president of Specialty Generics at Mallinckrodt, said the firm is "evaluating the FDA's letter and will request a meeting in the coming weeks to discuss it further.

"We continue to believe this new abuse-deterrent formulation has the potential to mitigate opioid abuse and misuse, and though we're disappointed by the FDA's decision, we will continue to pursue a pathway to try to gain approval of the drug.”

Prescription rates for opioid painkillers such as Roxicodone have increased dramatically in the US over the last two decades, in turn causing higher rates of addiction and abuse.

When taken in excess, the original non abuse-deterrent version of the drug can depress breathing to the point of causing severe lack of oxygen, coma, and death.