Clinical data
ATC code none
PubChem (CID) 51003467
ChemSpider 26617995
Chemical and physical data
Formula C27H29IN2O4
Molar mass 572.434 g/mol
3D model (Jmol) Interactive image

IBNtxA, or 3-iodobenzoyl naltrexamine, is an atypical opioid analgesic drug derived from naltrexone. In animal studies it produces potent analgesic effects that are blocked by levallorphan and so appear to be μ-opioid mediated, but it fails to produce constipation or respiratory depression, and is neither rewarding or aversive in conditioned place preference protocols. These unusual properties are thought to result from agonist action at a splice variant or heterodimer of the μ-opioid receptor, rather than at the classical full length form targeted by conventional opioid drugs.[1][2][3][4]


  1. Majumdar S, Grinnell S, Le Rouzic V, Burgman M, Polikar L, Ansonoff M, Pintar J, Pan YX, Pasternak GW. Truncated G protein-coupled mu opioid receptor MOR-1 splice variants are targets for highly potent opioid analgesics lacking side effects. Proceedings of the National Academy of Sciences USA. 2011 Dec 6;108(49):19778-83. PMID 22106286
  2. Majumdar S, Subrath J, Le Rouzic V, Polikar L, Burgman M, Nagakura K, Ocampo J, Haselton N, Pasternak AR, Grinnell S, Pan YX, Pasternak GW (2012). "Synthesis and evaluation of aryl-naloxamide opiate analgesics targeting truncated exon 11-associated μ opioid receptor (MOR-1) splice variants". J. Med. Chem. 55 (14): 6352–62. doi:10.1021/jm300305c. PMC 3412067Freely accessible. PMID 22734622.
  3. Wieskopf JS, Pan YX, Marcovitz J, Tuttle AH, Majumdar S, Pidakala J, Pasternak GW, Mogil JS (2014). "Broad-spectrum analgesic efficacy of IBNtxA is mediated by exon 11-associated splice variants of the mu-opioid receptor gene". Pain. 155 (10): 2063–70. doi:10.1016/j.pain.2014.07.014. PMID 25093831.
  4. Grinnell SG, Majumdar S, Narayan A, Le Rouzic V, Ansonoff M, Pintar JE, Pasternak GW (2014). "Pharmacologic characterization in the rat of a potent analgesic lacking respiratory depression, IBNtxA". J. Pharmacol. Exp. Ther. 350 (3): 710–8. doi:10.1124/jpet.114.213199. PMID 24970924.

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