Methadone, sold under the brand names Dolophine among others, is an synthetic opioid that is used as the hydrochloride to treat pain and as maintenance therapy or to help with detoxification in people with opioid dependence. Methadone hydrochloride is a mu-agonist; a synthetic opioid analgesic with multiple actions qualitatively similar to those of morphine. Some data also indicate that methadone acts as an antagonist at the NMDA-receptor. The contribution of NMDA receptor antagonism to methadone’s efficacy is unknown. Most common adverse reactions are: lightheadedness, dizziness, sedation, nausea, vomiting, and sweating. Avoid use mixed agonist/antagonist and partial agonist opioid analgesics with DOLOPHINE because they may reduce analgesic effect of DOLOPHINE or precipitate withdrawal symptoms.

Dimepheptanol is one of the phenylpiperidine series, an opioid receptor agonist, which is active as an opioid analgesic. It is also elaborated in a number of close analogues, derivatives or diastereoisomers with similar properties. Dimepheptanol is a synthetic narcotic analgesic that has no accepted medical use in the United States.

levomethadone, or R-(−)-methadone, is the active enantiomer of methadone; having approximately 50x the potency of the S-(+)-enantiomer as well as greater μ-opioid receptor selectivity.