Article · Wikipedia archive · Last revised Jul 23, 2026

Β-Funaltrexamine

β-Funaltrexamine (β-FNA) is an irreversible opioid antagonist that was used to create the first crystal structure of the μ-opioid receptor (MOR). It is selective for antagonism of the MOR over the δ-opioid receptor (DOR) and κ-opioid receptor (KOR). Chemically, it is a naltrexone derivative with a methyl-fumaramide group in the 6-position. In addition to its MOR irreversible antagonism, β-FNA is a reversible agonist of the κ-opioid receptor (KOR) and produces KOR-mediated analgesic effects in animals. This has limited its usefulness and contributed to the development of methocinnamox as a more selective functionally irreversible antagonist of the MOR with no significant opioid agonistic actions.

Last revised
Jul 23, 2026
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≈ 1 min
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β-Funaltrexamine
Clinical data
Other namesFunaltrexamine; β-Funaltrexamine; Beta-Funaltrexamine; β-FNA; Beta-FNA
Identifiers
  • methyl (E)-4-[[(4R,4aS,7R,7aR,12bS)-3-(cyclopropylmethyl)-4a,9-dihydroxy-1,2,4,5,6,7,7a,13-octahydro-4,12-methanobenzofuro[3,2-e]isoquinolin-7-yl]amino]-4-oxobut-2-enoate
    or
    Methyl (2E)-4-{[17-(cyclopropylmethyl)-3,14-dihydroxy-4,5α-epoxymorphinan-6β-yl]amino}-4-oxobut-2-enoate
CAS Number
PubChem CID
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
Chemical and physical data
FormulaC25H30N2O6
Molar mass454.523 g·mol−1
3D model (JSmol)
  • COC(=O)/C=C/C(=O)N[C@@H]1CC[C@]2([C@H]3CC4=C5[C@]2([C@H]1OC5=C(C=C4)O)CCN3CC6CC6)O
  • InChI=1S/C25H30N2O6/c1-32-20(30)7-6-19(29)26-16-8-9-25(31)18-12-15-4-5-17(28)22-21(15)24(25,23(16)33-22)10-11-27(18)13-14-2-3-14/h4-7,14,16,18,23,28,31H,2-3,8-13H2,1H3,(H,26,29)/b7-6+/t16-,18-,23+,24+,25-/m1/s1
  • Key:PQKHESYTSKMWFP-WZJCLRDWSA-N

β-Funaltrexamine (β-FNA) is an irreversible (covalently bonding) opioid antagonist that was used to create the first crystal structure of the μ-opioid receptor (MOR).1 It is selective for antagonism of the MOR over the δ-opioid receptor (DOR) and κ-opioid receptor (KOR).2 Chemically, it is a naltrexone derivative with a methyl-fumaramide group in the 6-position. In addition to its MOR irreversible antagonism, β-FNA is a reversible agonist of the κ-opioid receptor (KOR) and produces KOR-mediated analgesic effects in animals.234 This has limited its usefulness and contributed to the development of methocinnamox as a more selective functionally irreversible antagonist of the MOR with no significant opioid agonistic actions.3

See also

See also

References

References

  1. Manglik A, Kruse AC, Kobilka TS, Thian FS, Mathiesen JM, Sunahara RK, et al. (March 2012). "Crystal structure of the µ-opioid receptor bound to a morphinan antagonist". Nature. 485 (7398): 321–6. Bibcode:2012Natur.485..321M. doi:10.1038/nature10954. PMC 3523197. PMID 22437502.
  2. Ward SJ, Portoghese PS, Takemori AE (June 1982). "Pharmacological profiles of beta-funaltrexamine (beta-FNA) and beta-chlornaltrexamine (beta-CNA) on the mouse vas deferens preparation". Eur J Pharmacol. 80 (4): 377–384. doi:10.1016/0014-2999(82)90083-8. PMID 6286325.
  3. Broadbear JH, Sumpter TL, Burke TF, Husbands SM, Lewis JW, Woods JH, Traynor JR (September 2000). "Methocinnamox is a potent, long-lasting, and selective antagonist of morphine-mediated antinociception in the mouse: comparison with clocinnamox, beta-funaltrexamine, and beta-chlornaltrexamine". J Pharmacol Exp Ther. 294 (3): 933–940. PMID 10945843.
  4. Qi JA, Heyman JS, Sheldon RJ, Koslo RJ, Porreca F (March 1990). "Mu antagonist and kappa agonist properties of beta-funaltrexamine (beta-FNA) in vivo: long-lasting spinal analgesia in mice". J Pharmacol Exp Ther. 252 (3): 1006–1011. PMID 2156986.