8-Carboxamidocyclazocine (8-CAC) is an opioid analgesic drug related to cyclazocine, invented by medicinal chemist Mark P. Wentland and co-workers in Cogswell Laboratory at Rensselaer Polytechnic Institute. Similarly to cyclazocine, 8-CAC acts as an agonist at both the μ and κ opioid receptors, but has a much longer duration of action than cyclazocine, and does not have μ antagonist activity. Unexpectedly it was discovered that the phenolic hydroxyl group of cyclazocine could be replaced by a carboxamido group with only slight loss of potency at opioid receptors, and this discovery has subsequently been used to develop a large number of novel opioid derivatives where the phenolic hydroxy group has been replaced by either carboxamide or a variety of larger groups. Due to their strong κ-opio