Opana ER is an opioid medication. It helps treat moderate to severe pain. The extended-release form of oxymorphone is for around-the-clock treatment of pain or should not use-as-needed basis for pain. You can even buy Opana ER doses namely Opana ER 10 mg, Opana ER 15 mg, Opana ER 40 mg, Opana ER 30 mg, and Opana ER 5 mg.