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In pharmacology, methadone is a "synthetic opioid that is used as the hydrochloride. It is an opioid analgesic that is primarily a mu-opioid agonist. It has actions and uses similar to those of morphine. It also has a depressant action on the cough center and may be given to control intractable cough associated with terminal lung cancer. Methadone is also used as part of the treatment of dependence on opioid drugs, although prolonged use of methadone itself may result in dependence. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1082-3)."[1]



Methadone is metabolized by cytochrome P-450.

Adverse effects

Methadone may prolong the QT interval leading to Torsades de pointes. Clinical practice guidelines address screening for abnormal QT intervals.[2] However, these guidelines have been criticized for methodologicl problems and conflict of interests.[3]


  1. Anonymous (2020), Methadone (English). Medical Subject Headings. U.S. National Library of Medicine.
  2. QTc Interval Screening in Methadone Treatment. Annals of Internal Medicine (2009).
  3. Saitz R (2009). Follow-Up on QT Interval Screening During Methadone Treatment. Journal Watch (General). Retrieved on 2009-05-08.