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Systematic (IUPAC) name
Clinical data
Legal status
ATC code None
PubChem CID 51003467
Chemical data
Formula C27H29IN2O4 
Mol. mass 572.434 g/mol

IBNtxA is an atypical opioid analgesic drug derived from naltrexone. In animal studies it produces potent analgesic effects which 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]


  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