Methadone is an opioid analgesic that functions as a mu-opioid agonist. Generally used for maintenance and detoxification treatment of narcotic addiction, methadone can also be used for severe pain relief and to control intractable coughs associated with terminal lung cancers.

Methadone offers a similar effect to that of morphine, but the onset of the drug is slower with less severe symptoms and a more prolonged course.

Overdosing of methadone can cause cardiac arrest, apnea and circulatory collapse, and can result in death, particularly if administered via intravenous route. Methadone is a controlled drug in most areas, and can only be administered by trained healthcare professionals such as pharmacists.