Background: Cebranopadol, a promising opioid analgesic undergoing phase III trials, was developed for the treatment of acute and chronic moderate-to-severe pain. Because it is a non-selective ligand acting at more than one member of the opioid receptor family, combining a dual agonist action on mu-, delta-, and kappa-opioid receptors (MOR, DOR, and KOR) and nociceptin/orphanin FQ peptide (NOP) receptors, it has...