A drug used to treat moderate to severe pain. It is also used as a sedative before surgery, to help with anesthesia during surgery, during labor, and to treat anxiety caused by some medical conditions. It is made from morphine and binds to opioid receptors in the central nervous system. Oxymorphone hydrochloride is a type of opioid and a type of analgesic agent. Also called Numorphan and Opana.