norbuprenorphine norbuprenorphine norbuprenorphine is a major active metabolite of the opioid modulator buprenorphine. it is a μ-opioid, δ-opioid, and nociceptin receptor full agonist, and a κ-opioid receptor partial agonist. in rats, unlike buprenorphine, norbuprenorphine produces marked respiratory depression but with very little antinociceptive effect. in explanation of these properties, norbuprenorphine has been found to be a high affinity p-glycoprotein substrate, and in accordance, shows very limited blood-brain-barrier penetration. norbuprenorhine norbuprenorphineclinical dataatc codenoneidentifiers iupac name (5α,6β,14β,18r)-18--6-methoxy-18,19-dihydro-4,5-epoxy-6,14-ethenomorphinan-3-ol cas number78715-23-8pubchem cid114976chemspider102911unii7e53b4o073comptox dashboard (epa)dtxsid60891436 echa infocard100.208.387 chemical and physical dataformulac25h35no4molar mass413.558 g·mol−13d model (jsmol)interactive image smiles c(1c23cc1(425ccn3cc6c5c(c(cc6)o)o4)oc)(c(c)(c)c)o inchi inchi=1s/c25h35no4/c1-21(2,3)22(4,28)16-13-23-8-9-25(16,29-5)20-24(23)10-11-26-17(23)12-14-6-7-15(27)19(30-20)18(14)24/h6-7,16-17,20,26-28h,8-13h2,1-5h3/t16-,17-,20-,22+,23-,24+,25-/m1/s1key:yoyllrbmgqrftn-iombulrvsa-n