Asimadoline is a potent κ opioid receptor agonist with IC₅₀s of 5.6 and 1.2 nM for guinea pig and human recombinant κ opioid receptor, respectively. IC50 & Target: IC50: 5.6 nM (guinea pig κ opioid), 1.2 nM (human recombinant κ opioid)^[1] In Vitro: The IC₅₀ for Asimadoline binding to μ-opioid receptors is 3 µM and to δ-opioid receptors is 0.7 µM. The IC₅₀ values for D1, D2, kainate, σ, PCP/NMDA, H1, α1, α2, M1/M2, glycine, 5HT1A, 5HT1C, 5HT1D, 5HT2, 5HT3, AMPA and kainate/AMPA receptors are all >10 IC₅₀, suggesting no relevant antihistaminergic, antiserotonergic or anticholinergic effects. At high concentrations, Asimadoline demonstrates spasmolytic action against 400 µM barium chloride in the rat duodenum (IC₅₀=4.2 µM), suggesting that Asimadoline may block the direct stimulant effects of barium on smooth muscle through mechanisms that are not identified^[1]. In Vivo: The absorption rate following oral administration is 80% in rats and >90% in dogs and monkeys. The metabolism of Asimadoline is rapid and appears similar in animals and man. Asimadoline has peripheral anti-inflammatory actions that are partly mediated through increase in joint fluid substance P levels^[1]. Treatment with Asimadoline (5 mg/kg/day i.p.) produces marked (and sustained) attenuation of the disease with all three time regimes^[2].