A potent antagonist for the human IP (prostacyclin) receptor that antagonizes the carbaprostacyclin-induced activation of human neuroblastoma adenylate cyclase, blocking cAMP accumulation in a dose-dependent manner; inhibits the binding of tritiated iloprost to rodent neuroblastoma cells (Ki = about 1.5 nM); shows significant analgesic activity in standard antinociceptive assays at levels between 2-20 mg/kg