Disopyramide

Disopyramide is a class Ia sodium channel blocker and a pyridine derivative. During the depolarization phase of the cardiac action potential, disopyramide inhibits sodium channels, reducing the rate of action potential upstroke, slowing myocardial conduction, and suppressing abnormal automaticity. At the same time, it partially inhibits potassium channels, prolonging the action potential duration and the effective refractory period, which helps block reentry circuits. Because disopyramide also blocks M2 receptors, it can increase heart rate and accelerate atrioventricular conduction. This property may offset part of its antiarrhythmic effect and may also cause side effects such as dry mouth, urinary retention, blurred vision, and constipation.