A mixed δ-opioid receptor antagonist and μ-opioid receptor agonist; binds with high affinity to the rat δ-, rat μ-, and human μ-opioid receptors (Kis = 1.3, 0.9, and 1.7 nM, respectively); reduced GI transit and fecal output to control levels (at 5-100 mg/kg) in a guinea pig model of GI stress; reduced symptoms of IBS with diarrhea in clinical trials