5'-guanidinonaltrindole 5'-guanidinonaltrindole 5'-guanidinonaltrindole (5'-gnti) is an opioid antagonist used in scientific research which is highly selective for the κ opioid receptor. it is 5x more potent and 500 times more selective than the commonly used κ-opioid antagonist norbinaltorphimine. it has a slow onset and long duration of action, and produces antidepressant effects in animal studies. it also increases allodynia by interfering with the action of the κ-opioid peptide dynorphin. 5'-guanidinonaltrindoleclinical dataother names5'-guanidinonaltrindole, gntiidentifiers iupac name 5'-guanidinyl-17-(cyclopropylmethyl)-6,7-dehydro-4,5α-epoxy-3,14-dihydroxy-6,7-2',3'-indolomorphinan pubchem cid6604846iuphar/bps1669chemspider21259050 nchemblchembl330427 nchemical and physical dataformulac27h29n5o3molar mass471.561 g·mol−13d model (jsmol)interactive image smiles c1cc2c(cc1nc(=n)n)c3c(2)456ccn((5(c3)o)cc7c6c(c(cc7)o)o4)cc8cc8 inchi inchi=1s/c27h29n5o3/c28-25(29)30-15-4-5-18-16(10-15)17-11-27(34)20-9-14-3-6-19(33)23-21(14)26(27,24(35-23)22(17)31-18)7-8-32(20)12-13-1-2-13/h3-6,10,13,20,24,31,33-34h,1-2,7-9,11-12h2,(h4,28,29,30)/t20-,24+,26+,27-/m1/s1 nkey:vlnhdkdbgwxjee-gyhunedqsa-n n ny (what is this?) (verify) in addition to activity at the kor, 5'-gnti has been found to act as a positive allosteric modulator of the α1a-adrenergic receptor (ec50 = 41 nm), and this may contribute to its "severe transient effects".