a synthetic narcotic drug, CHNO, used in medicine to treat heroin and morphine addicts: it is more potent than morphine, with a longer duration of action and milder withdrawal symptoms
See methadone in American Heritage Dictionary 4
(mĕthˈə-dōnˌ)
noun
A potent synthetic narcotic drug, C21H27NO, that is less addictive than morphine or heroin and is used as a substitute for these drugs in addiction treatment programs. It may also be used for chronic pain management.