Asimadoline hydrochloride (EMD-61753 hydrochloride) is a κ-opioid receptor agonist potentially for the treatment of pruritus. Asimadoline hydrochloride has also been shown to be used in the treatment of irritable bowel syndrome.

κ opioid (human recombinant):1.2 nM (EC50), κ opioid (Guinea pig):5.6 nM (EC50)

The IC50 for Asimadoline binding to μ-opioid receptors is 3 μM and to δ-opioid receptors is 0.7 μM. 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].

The metabolism of Asimadoline is rapid and appears similar in animals and man. The absorption rate following oral administration is 80% in rats and >90% in dogs and monkeys. Asimadoline has peripheral anti-inflammatory actions that are partly mediated through an 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].

Asimadoline (5 mg/kg/day, n=10 per group) or vehicle (2 mL/kg/day, n=10) is administered to DA rats by i.p. injection twice daily (i) during the primary inflammatory phase (days 1–3); (ii) once the disease is established (days 13–21); or (iii) throughout the entire time course (days 1-21). Non-arthritic control animals receive Asimadoline (5 mg/kg/day, n=5) or vehicle (2 mL/kg/day, n=5) by i.p. injection twice daily. In all cases, disease parameters are assessed. In this experiment, the SP content of joint tissue is assessed only after the rats are killed (day 21)[2].