Bretylium blocks the release of noradrenaline from the peripheral sympathetic nervous system, and is used in emergency medicine, cardiology, and other specialties for the acute management of ventricular tachycardia and ventricular fibrillation. The primary mode of action for bretylium is thought to be inhibition of voltage-gated K(+) channels. Recent evidence has shown that bretylium may also inhibit the Na,K-ATPase by binding to the extracellular K-site.   From: DrugBank