Blocker of I Kur ultrarapid delayed rectifier potassium current and K V 1.5 channels (IC 50 = 0.31 μ M for rK V 1.5). Displays selectivity for inhibition of I Kur over I to (8-fold), I K1 , I Kr and I Ks (20-fold) in native myocytes and selectivity for rat recombinant K V 1.5 over K V 3.1 (~ 15-fold). Increases action potential duration in atrial but not ventricular myocytes and prevents atrial arrhythmia.
