An antiarrythmic agent that inhibits potassium channels; an inhibitor of the rapidly activating inward rectifying component of net delayed rectifier K+ current (IC50 = 31.5 nM in guinea pig cardiomyocytes); has pro-arrhythmic activity at 1 μM, inducing early afterdepolarizations in cells and Torsade de Pointes in a rabbit screen for proarrhythmic properties at a dose of 10 mg/kg