Methadone (Dolophine®, Amidone®, Methadose®, Physeptone®, Heptadon® and many others) is a synthetic opioid, used medically as an analgesic, antitussive and a maintenance anti-addictive for use in patients on opioids. It was developed in Germany in 1937. Although chemically unlike morphine or heroin, methadone also acts on the opioid receptors and thus produces many of the same effects. Methadone is also used in managing chronic pain due to its long duration of action and very low cost. In late 2004, the cost of a one-month supply of methadone was $20, as compared to an equivalent analgesic amount of Demerol (pethidine) at $120, up to $500 and more for Palladone® (hydromorphone), MS-Contin® (morphine) and Duragesic® (fentanyl) as well as the Opana® series of extended-release oxymorphone.

Methadone's usefulness in treatment of opioid dependence is the result of its cross-tolerance with other opioids including heroin, morphine, etc. and long duration of effects with the result that oral dosing with methadone will stabilise the condition of the patient by stopping and preventing the opioid withdrawal syndrome and getting patients off the needle by at least partially blocking the "rush" resulting from intravenous injection of heroin, morphine, and similar drugs.

Today a number of pharmaceutical companies produce and distribute methadone, with only the racaemic hydrochloride being available in the United States as of March 2008 but the tartrate and other salts of the laevorotary form (levomethadone, with trade names like Polamidone®, Heptadon® etc.) -- which is many times more potent and lacks the cardiac effects like lengthened QT interval caused by the dextrorotary form -- being available in Europe and elsewhere. The major producer remains Mallinckrodt. Mallinckrodt sells bulk methadone to most of the producers of generic preparations and also distributes its own brand name product in the form of tablets, dispersible tablets and oral concentrate under the name Methadose in the United States.