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Elimination half-life3-6 hours
CAS Number
PubChem CID
ECHA InfoCard100.004.320 Edit this at Wikidata
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Molar mass271.397 g/mol g·mol−1
3D model (JSmol)
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Levomethorphan (INN, BAN) is an opioid analgesic of the morphinan family that has never been marketed.[1] It is the L-stereoisomer of racemethorphan (methorphan).[1] The effects of the two isomers of the racemethorphan are quite different, with dextromethorphan (DXM) being an antitussive at low doses and a dissociative hallucinogen at much higher doses.[2] It is about five times stronger than morphine. [3]

Levomethorphan is a prodrug to levorphanol, analogously to DXM acting as a prodrug to dextrorphan or codeine behaving as a prodrug to morphine.[4] As such, levomethorphan has similar effects to levorphanol but is less potent as it must be demethylated to the active form by liver enzymes before being able to produce its effects.[4] As a prodrug of levorphanol, levomethorphan functions as a potent agonist of all three of the opioid receptors, μ, κ1 and κ3 but notably not κ2), and δ, as an NMDA receptor antagonist, and as a serotonin-norepinephrine reuptake inhibitor.[4] Via activation of the KOR, levomethorphan can produce dysphoria and psychotomimetic effects such as dissociation and hallucinations.[5]

Levomethorphan is listed under the Single Convention on Narcotic Drugs 1961 and is regulated like morphine in most countries. In the United States it is a Schedule II Narcotic controlled substance with a DEA ACSCN of 9210 and 2014 annual aggregate manufacturing quota of 195 grammes, up from 6 grammes the year before. The salts in use are the tartrate (free base conversion ratio 0.644) and hydrobromide (0.958).[6] At the current time, no levomethorphan pharmaceuticals are marketed in the United States.

See also[edit]


  1. ^ a b J. Elks (14 November 2014). The Dictionary of Drugs: Chemical Data: Chemical Data, Structures and Bibliographies. Springer. pp. 656–. ISBN 978-1-4757-2085-3.
  2. ^ Joseph M. Hornback (31 January 2005). Organic Chemistry. Cengage Learning. pp. 243–. ISBN 0-534-38951-1.
  3. ^ Handbook of Analytical Therapeutic Drug Monitoring and Toxicology Google books preview
  4. ^ a b c Gudin, Jeffrey; Fudin, Jeffrey; Nalamachu, Srinivas (2015). "Levorphanol use: past, present and future". Postgraduate Medicine. 128 (1): 46–53. doi:10.1080/00325481.2016.1128308. ISSN 0032-5481.
  5. ^ Eduardo D. Bruera; Russell K. Portenoy (12 October 2009). Cancer Pain: Assessment and Management. Cambridge University Press. pp. 215–. ISBN 978-0-521-87927-9.
  6. ^ http://www.deadiversion.usdoj.gov/quotas/conv_factor/index.html