Novel antagonist selective for the vascular form of Kir6 (KATP) channel; inhibits Kir6 currents in isolated mesenteric artery smooth muscle cells (Kd = 65 nM) but not in cardiac or skeletal myocytes. Inhibits blood vessel relaxation and hypotension induced by pinacidil in vivo. Displays weak diuretic effects. Purity 99%. MW (observed): 381.98