nalodeine nalodeine nalodeine, also known more commonly as n-allylnorcodeine, is an opioid antagonist (specifically, an antagonist of the μ-opioid receptor) that was never marketed but is notable as the first opioid antagonist to be discovered. it was first reported in 1915 and was found to block the effects of morphine in animals. this was followed by the clinical introduction of nalorphine (n-allylnormorphine) in 1954, naloxone (n-allyloxymorphone) in 1960, and naltrexone (n-methylcyclopropyloxymorphone) in 1963. nalmefene (6-desoxy-6-methylene-naltrexone), another structurally related opioid antagonist derivative, was also subsequently introduced, in 1996. in animals, nalodeine both reverses morphine- and heroin-induced respiratory depression and acts as a respiratory stimulant in its own right (i.e., when given alone). similarly to nalorphine, nalodeine has also been found to act as an agonist of the κ-opioid receptor. nalodeineclinical dataother namesn-allylnorcodeineidentifiers iupac name (4r,4ar,7s,7ar,12bs)-9-methoxy-3-prop-2-enyl-2,4,4a,7,7a,13-hexahydro-1h-4,12-methanobenzofuroisoquinoline-7-ol cas number56195-50-7 ypubchem cid5486632chemspider4588998uniiyd9m6bel6schemical and physical dataformulac20h23no3molar mass325.408 g·mol−13d model (jsmol)interactive image smiles coc1=c2c3=c(cc4c5c3(ccn4cc=c)c(o2)c(c=c5)o)c=c1 inchi inchi=1s/c20h23no3/c1-3-9-21-10-8-20-13-5-6-15(22)19(20)24-18-16(23-2)7-4-12(17(18)20)11-14(13)21/h3-7,13-15,19,22h,1,8-11h2,2h3/t13-,14+,15-,19-,20-/m0/s1key:xaowelgmjqtjqr-wyioclovsa-n