|AHFS/Drugs.com||International Drug Names|
|Oral, IV, IM, SC, IT|
|Elimination half-life||~18 hours|
|Chemical and physical data|
|Molar mass||309.445 g/mol g·mol−1|
|3D model (JSmol)|
Levomethadone (INN; L-Polamidon, L-Polamivet, Levadone, Levothyl), or levamethadone, is a synthetic opioid analgesic and antitussive which is marketed in Europe and is used for pain management and in opioid maintenance therapy. In addition to being used as a pharmaceutical drug itself, 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. Accordingly, it is about twice as potent as methadone by weight and its effects are virtually identical in comparison. In addition to its activity at the opioid receptors, levomethadone has been found to act as a weak competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor complex and as a potent noncompetitive antagonist of the α3β4 nicotinic acetylcholine (nACh) receptor.
Where it is used, levomethadone is used for narcotic maintenance in place of, or in some cases alongside as an alternative, to racaemic methadone, owing to concern about the cardiotoxic and QT-prolonging action of racaemic methadone being exclusively caused by the dextro isomer.
The separation of the stereoisomers is one of the easier in organic chemistry and is described in the original patent. It involves "treatment of racemic methadone base with d-(+)-tartaric acid in an acetone/water mixture [which] precipitates almost solely the dextro-methadone levo-tartrate, and the more potent levo-methadone can easily be retrieved from the mother liquor in a high state of optical purity" 
Levomethadone is listed under the Single Convention On Narcotic Drugs 1961 and is a Schedule II Narcotic controlled substance in the US as an isomer of methadone (ACSCN 9250) and is not listed separately, nor is dextromethadone. It is similarly controlled under the German Betäubungsmittelgesetz and similar laws in practically every other country.
- Helmut Buschmann (20 December 2002). Analgesics: From Chemistry and Pharmacology to Clinical Application. Wiley-VCH. p. 196. ISBN 978-3-527-30403-5. Retrieved 17 May 2012.
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- Eric C. Strain; Maxine L. Stitzer (4 November 2005). The Treatment of Opioid Dependence. JHU Press. p. 63. ISBN 978-0-8018-8303-3. Retrieved 19 May 2012.
- Xiao Y, Smith RD, Caruso FS, Kellar KJ (October 2001). "Blockade of rat alpha3beta4 nicotinic receptor function by methadone, its metabolites, and structural analogs". The Journal of Pharmacology and Experimental Therapeutics. 299 (1): 366–71. PMID 11561100.
- Hull JD, Scheinmann F, Turner NJ (March 2003). "Synthesis of optically active methadones, LAAM and bufuralol by lipase-catalysed acylations". Tetrahedron: Asymmetry. 14 (5): 567–576. doi:10.1016/S0957-4166(03)00019-3.
- US patent 6143933