Antinociceptive effects of SC-39566, an opioid dipeptide arylalkylamide, in the Rhesus monkey

This study evaluated the antinociceptive activity of an opioid dipeptide arylalkylamide, SC-39566 (2,6-dimethyl-L-tyrosinyl-D-alanyl-(3-phenyl-l-propyl)- amide), in the Rhesus monkey using the discrete trial, intermittent shock titration paradigm. I.m. administration of doses ranging from 12 to 24 mg/kg produced a dose-dependent increase in escape threshold and a dose-dependent rightward shift in the frequency distribution of responses to suprathreshold electrocutaneous stimuli. Although equivalent with respect to efficacy, SC-39566 was only one-fourth to one-sixth as potent as morphine in this paradigm. This study is the first report of the antinociceptive activity of an opioid dipeptide arylalkylamide after systemic administration in the primate.