Opana is a brand name for the medication oxymorphone, which is an opioid analgesic used to treat severe pain that requires around-the-clock, long-term opioid treatment and for which alternative treatment options are inadequate. It's typically prescribed when other pain medications haven't been effective enough. Opana works by binding to opioid receptors in the brain and spinal cord, altering the way your body perceives and responds to pain.