Methadone hydrochloride is an opioid receptor agonist with effects similar to those of morphine. It has analgesic effect and can produce respiratory depression, pupil reduction and sedation. Compared with morphine, it has a relatively long duration of action, is not easily tolerated, and has low drug dependence. It is a synthetic alternative to morphine as a narcotic analgesic in Germany during World War II. In the early 1960s, this drug was found to have pharmacological effects for the treatment of heroin dependence detoxification and alternative maintenance treatment. Methadone is well absorbed orally, with an onset of action 30 minutes after administration and a peak blood concentration of 4 hours. The duration of action is 24-36 hours, with a half-life of 15-18 hours. The plasma protein binding rate is 85%-90% and is mainly metabolized in the liver and excreted by the kidneys and bile. Repeated administration has tissue accumulation effects. Indications are: i. For analgesic treatment of severe pain caused by trauma and postoperative cancer. II. For the detoxification treatment of opioid dependence. Third, for alternative maintenance treatment of opioid dependence.