Clinical data
ATC code
  • None
  • (5α)-3,14-dihydroxy-17-(3-methyl-2-buten-1-yl)-4,5-epoxymorphinan-6-one
CAS Number
PubChem CID
CompTox Dashboard (EPA)
Chemical and physical data
Molar mass355.434 g·mol−1
3D model (JSmol)
  • O=C4[C@@H]5Oc1c2c(ccc1O)C[C@H]3N(CC[C@]25[C@@]3(O)CC4)C\C=C(/C)C
  • InChI=1S/C21H25NO4/c1-12(2)6-9-22-10-8-20-17-13-3-4-14(23)18(17)26-19(20)15(24)5-7-21(20,25)16(22)11-13/h3-4,6,16,19,23,25H,5,7-11H2,1-2H3/t16-,19+,20+,21-/m1/s1

Nalmexone (INN; also known as nalmexone hydrochloride (USAN) or by the development codes EN-1620A and UM-592) is a semisynthetic, opioid partial agonist or mixed agonist-antagonist with both analgesic and narcotic antagonist properties that was never marketed.[1][2][3][4] In clinical studies it was found to have comparable analgesic efficacy to morphine, though with several-fold reduced potency.[5] In addition, nalmexone's side effects, the most common of which were sleepiness and sweating, were reported to be similar to those of morphine, albeit with a noticeably higher degree of incidence.[5]


Nalmexone can be synthesized from oxymorphone:[6]

Nalmexone synthesis
Nalmexone synthesis

See also


  1. ^ Macdonald F (1997). Dictionary of Pharmacological Agents. CRC Press. p. 1395. ISBN 978-0-412-46630-4. Retrieved 11 May 2012.
  2. ^ Casy AF, Parfitt RT (1986). Opioid Analgesics: Chemistry and Receptors. Springer. p. 55. ISBN 978-0-306-42130-3. Retrieved 11 May 2012.
  3. ^ Loew GH, Berkowitz DS (1978). "Quantum chemical studies of N-substituent variation in the oxymorphone series of opiate narcotics". Journal of Medicinal Chemistry. 21 (1): 101–106. doi:10.1021/jm00199a018. PMID 73588.
  4. ^ Forrest WH, Shroff PF, Mahler DL (1972). "Analgesic and other effects of nalmexone in man". Clinical Pharmacology and Therapeutics. 13 (4): 520–525. doi:10.1002/cpt1972134520. PMID 4557582. S2CID 30780581.
  5. ^ a b Committee on Problems of Drug Dependence (1969). Bulletin, problems of drug dependence. National Academies. p. 5873. NAP:10503. Retrieved 11 May 2012.
  6. ^ Lowenstein, M. J.; Fishman, J.; 1967, U.S. patent 3,320,262