Mallinckrodt PLC's SpecGx LLC unit said the U.S. Food and Drug Administration rejected the company's application for opioid painkiller Roxicodone.

SpecGx, which operates the U.K. drugmaker's specialty generics business, received a complete response letter from the U.S. drug agency on the company's new drug application for the immediate-release reformulation of Roxicodone tablets.

The FDA provided guidance on areas of further evaluation necessary to resubmit the application for further review and potential approval of the medicine.

"We are evaluating the FDA's letter and will request a meeting in the coming weeks to discuss it further," said Matt Harbaugh, president of Mallinckrodt's specialty generics division.

Roxicodone, also known as oxycodone hydrochloride, is used to manage pain severe enough to require an opioid analgesic and for which alternative treatments are inadequate. The drug was designed with properties to deter intravenous and intranasal abuse.

Mallinckrodt develops, makes and distributes specialty pharmaceutical products and therapies.