Levomethadone

Levomethadone, sold under the brand name L-Polamidon among others, is a synthetic opioid analgesic and antitussive which is marketed in Europe and is used for pain management and in opioid maintenance therapy.[1][2][3] In addition to being used as a pharmaceutical drug itself, levomethadone is the main therapeutic component of methadone.[2]

Levomethadone
Clinical data
Other namesLevamethadone; l-Methadone; 6R-Methadone; (–)-Methadone; R-(–)-Methadone; D-(–)-Methadone
AHFS/Drugs.comInternational Drug Names
Routes of
administration		By mouth, IV, IM, SC, IT[1]
ATC code
Legal status
Legal status
  • DE: Anlage III (Special prescription form required)
  • UK: Class A
  • US: Schedule II
  • UN: Narcotic Schedule I
Pharmacokinetic data
BioavailabilityHigh[1]
Protein binding60–90%[1]
Elimination half-life~18 hours[1]
Identifiers
CAS Number
PubChem CID
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
ECHA InfoCard100.120.592
Chemical and physical data
FormulaC21H27NO
Molar mass309.445 g·mol−1
3D model (JSmol)
Melting point99.5 °C (211.1 °F)
Solubility in water48.48 mg/mL (20 °C)

Where it is used, levomethadone is used for narcotic maintenance in place of, or in some cases alongside as an alternative, to racemic methadone, owing to concern about the cardiotoxic and QT-prolonging action of racemic methadone being exclusively caused by the dextrorotatory enantiomer, dextromethadone.

Pharmacology

Pharmacodynamics

Levomethadone has approximately 50x the potency of the S-(+)-enantiomer as well as greater μ-opioid receptor selectivity.[1][4] Accordingly, it is about twice as potent as methadone by weight and its effects are virtually identical in comparison.[5][6] 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[7] and as a potent noncompetitive antagonist of the α3β4 nicotinic acetylcholine (nACh) receptor.[8]

Methadone at opioid receptors, monoamine transporters, and the NMDA receptor
CompoundAffinities (Ki)Ratios
MORDORKORSERTNETNMDARMOR:DOR:KORSERT:NET
Methadone1.7 nM435 nM405 nMNDND2,500–8,300 nM1:256:238ND
  Dextromethadone19.7 nM960 nM1,370 nM992 nM12,700 nM2,600–7,400 nM1:49:701:13
  Levomethadone0.945 nM371 nM1,860 nM14.1 nM702 nM2,800–3,400 nM1:393:19681:50
Sources: See template.

Chemistry

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" [9]

There is now an asymmetric synthesis[10] available to prepare both levomethadone (R-(−)-methadone) and dextromethadone (S-(+)-methadone).[11]

Society and culture

Generic names

Levomethadone is the generic name of the drug and its INN.[3][2]

Brand names

Levomethadone has been sold under brand names including L-Polaflux, L-Polamidon, L-Polamivet, Levadone, Levo-Methasan, Levothyl, Mevodict, and Vistadict, among others.[12][3][2]

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.[13] It is similarly controlled under the German Betäubungsmittelgesetz and similar laws in practically every other country.

References
  1. 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.
  2. F.. Macdonald (1997). Dictionary of Pharmacological Agents. CRC Press. p. 1294. ISBN 978-0-412-46630-4. Retrieved 17 May 2012.
  3. Index Nominum 2000: International Drug Directory. Taylor & Francis US. 2000. p. 605. ISBN 978-3-88763-075-1. Retrieved 17 May 2012.
  4. Renate Förch; Holger Schönherr; A. Tobias A. Jenkins (11 August 2009). Surface Design: Applications in Bioscience and Nanotechnology. Wiley-VCH. p. 193. ISBN 978-3-527-40789-7. Retrieved 17 May 2012.
  5. Eduardo Bruera; Sriram Yennurajalingam (16 August 2011). Oxford American Handbook of Hospice and Palliative Medicine. Oxford University Press. p. 43. ISBN 978-0-19-538015-6. Retrieved 17 May 2012.
  6. Verthein U, Ullmann R, Lachmann A, et al. (November 2005). "The effects of racemic D,L-methadone and L-methadone in substituted patients--a randomized controlled study". Drug and Alcohol Dependence. 80 (2): 267–71. doi:10.1016/j.drugalcdep.2005.04.007. PMID 15916866.
  7. 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.
  8. 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.
  9. https://www.erowid.org/archive/rhodium/chemistry/methadone.html
  10. 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.
  11. US patent 6143933
  12. https://www.drugs.com/international/levomethadone.html
  13. http://www.deadiversion.usdoj.gov/quotas/conv_factor/index.html


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