SCH-23390 hydrochloride (R-(+)-SCH-23390, SCH-23390) is a highly potent and selective dopamine D1-like receptor antagonist with Ki of 0.2 nM and 0.3 nM for the D1 and D5 dopamine receptor subtypes, respectively. SCH-23390 hydrochloride is a potent and high efficacy agonist at h5-HT2C receptors with Ki of 9.3 nM. SCH-23390 hydrochloride directly inhibits G protein-coupled inwardly rectifying potassium (GIRK) channels with IC50 of 268 nM.