A painkiller on prescription is called Opana ER. It was initially authorized in 2006 to treat moderate to severe pain. When a continuous, round-the-clock opioid analgesic is required for a protracted period of time, you may Buy Opana ER online. The painkiller oxymorphone is used to treat moderate to severe pain. It is a member of the opioid analgesic drug class. It alters how your body perceives and reacts to pain by acting on the brain.