SCH-23390 hydrochloride (R-(+)-SCH-23390 hydrochloride) is a potent and selective dopamine D 1 -like receptor antagonist with K i s of 0.2 nM and 0.3 nM for the D 1 and D 5 receptor , respectively. SCH-23390 hydrochloride is a potent and high efficacy human 5-HT 2C receptor agonist with a K i of 9.3 nM. SCH-23390 hydrochloride also binds with high affinity to the 5-HT 2 and 5-HT 1C receptors . SCH-23390 hydrochloride inhibits G protein-coupled inwardly rectifying potassium (GIRK) channels with an IC 50 of 268 nM.