The main drug component of methadone is methadone hydrochloride, which is a more common oral anesthetic analgesic, belonging to the opioid agonist. The main advantages of methadone hydrochloride are: relatively long duration of action, not easy to produce drug tolerance, dependence is relatively low. In addition, the analgesic effect of methadone hydrochloride is still relatively strong, and will mostly be used for severe pain caused by trauma, postoperative, cancer and so on. Because methadone hydrochloride has a relatively low drug dependence, it is commonly used for detoxification and substitution maintenance treatment for dependence on heroin or other drugs. Adverse effects of methadone hydrochloride should be noted and may include headache, respiratory depression, and constipation. It is important to follow the doctor’s instructions when taking the medication, but it is recommended to seek medical attention if you experience any physical symptoms.