PZM21 is a potent and selective μ opioid receptor agonist with an EC 50 of 1.8 nM In Vitro PZM21 has no detectable κOR or nociceptin receptor agonist activity-it is actually an 18 nM κOR antagonist-while it is a 500-fold weaker δOR agonist, making it a selective μOR agonist. At hERG, PZM21 has an IC 50 of between 2 and 4 μM, 500- to 1,000-fold weaker than its potency as a μOR agonist. Signalling by PZM21 and other μOR agonists appears to be mediated primarily by the heterotrimeric G protein Gi/o, as its effect on cAMP levels is eliminated by pertussis toxin and no activity is observed in a calcium release assay. MCE has not independently confirmed the accuracy of these methods. They are for reference only. In Vivo PZM21 is a potent Gi activator with exceptional selectivity for μOR and minimal β-arrestin-2 recruitment. PZM21 is efficacious for the affective component of analgesia versus the reflexive component and is devoid of respiratory depression in mice at equi-analgesic doses. PZM21 displays dose-dependent analgesia in a mouse hotplate assay, with a per cent maximal possible effect (% MPE) of 87% reached 15 min after administration of the highest dose of drug tested .PZM21 has a long-lasting analgesic effect on CNS mediated-pain responses, but does not cause respiratory depression and constipation, two key side effects of opioid agonists. MCE has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid IC50& Target:EC50: 1.8 nM (μ opioid receptor)