A potent κ-opioid receptor agonist (IC50s = 5.6 and 1.2 nM for guinea pig and human receptors, respectively); is 501- and 498-fold selective for κ-opioid over μ- and δ-opioid receptors, respectively; is spasmolytic in isolated rat duodenum (IC50 = 4.2 μM) and inhibits spontaneous contractions of isolated rat uterus (IC50 = 12.7 μM); reduces joint damage in a rat model of CFA-induced arthritis; reduces the abdominal withdrawal reflex in a model of visceral pain induced by colonic distension in wild-type mice at 25 mg/kg