Methadone hydrochloride is a hydrochloride. It contains a methadone. ChEBI Methadone Hydrochloride is the hydrochloride salt of methadone, a synthetic opioid with analgesic activity. Similar to morphine and other morphine-like agents, methadone mimics the actions of endogenous peptides at CNS opioid receptors, primarily the mu-receptor, resulting in characteristic morphine-like effects including analgesia, euphoria, sedation, respiratory depression, miosis, bradycardia and physical dependence. Because of the prolonged half-life of methadone compared to other morphine-like agents such as heroin, the onset of opiate withdrawal symptoms is slower, the duration of opiate withdrawal is prolonged, and opiate withdrawal symptoms are less severe. NCI Thesaurus (NCIt) A synthetic opioid that is used as the hydrochloride. It is an opioid analgesic that is primarily a mu-opioid agonist. It has actions and uses similar to those of MORPHINE. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1082-3) Medical Subject Headings (MeSH)