Methadone, also known as Dolophine among other brand names, is a synthetic opioid. It is used medically as a pain medication and a maintenance therapy in people with opioid dependence. Methadone is also used in managing severe chronic pain owing to its long duration of action and strong analgesic effect.Side effects are similar to that of other opioids.t is used medically as a pain medication and a maintenance therapy in people with opioid dependence. Methadone is also used in managing severe chronic pain owing to its long duration of action and strong analgesic effect.