Selective renal outer medullary potassium channel (ROMK, Kir1.1) antagonist (IC50 = 300 nM). Thought to block the intracellular pore of the ROMK channel. Exhibits no effect on Kir7.1 at concentrations up to 10 μM; does not inhibit Kir2.1, Kir2.3 or Kir4.1. Displays similar potency to VU 590 (Cat. No. 3891).