Potent and selective D1-like dopamine receptor antagonist (Ki~ 0.56 nM for D1; KB = 2 μM for D2). Also antagonist at the vascular 5-HT2 receptor (Ki = 11 nM). Displays selective inhibition of adenylyl cyclase 2 (AC2); inactive against AC1 or AC5. Centrally active following systemic administration in vivo. Purity 98%. MW (observed): 413.15