Bretylium

Mechanism action of Bretylium

Bretylium inhibits norepinephrine release by depressing adrenergic nerve terminal excitability. The mechanisms of the antifibrillatory and antiarrhythmic actions of bretylium are not established. In efforts to define these mechanisms, the following electrophysiologic actions of bretylium have been demonstrated in animal experiments: increase in ventricular fibrillation threshold, increase in action potential duration and effective refractory period without changes in heart rate, little effect on the rate of rise or amplitude of the cardiac action potential (Phase 0) or in resting membrane potential (Phase 4) in normal myocardium, decrease in the disparity in action potential duration between normal and infarcted regions, and increase in impulse formation and spontaneous firing rate of pacemaker tissue as well as increase ventricular conduction velocity.