An NK1 receptor antagonist (Ki = 0.95 nM); selective for human NK1 over human NK2 and NK3 and rat NK1 (Kis = >1,500 nM); selective for NK1 over 50 G protein-coupled receptors, monoamine transporters, and ion channels when used in the nanomolar range; decreases the maximal response to substance P in isolated guinea pig ileum; inhibits substance P-induced scratching, biting, and licking in mice at doses of 1-10 mg/kg; decreases NK agonist-induced foot tapping in gerbils (ID50s = 1.5 mg/kg, i.p., or 0.5 mg/kg, oral).