Which class of antidysrhythmic medication blocks sodium channels?

The correct choice is Class I antidysrhythmic medication, which is known for its mechanism of action of blocking sodium channels. This class of drugs works primarily by inhibiting sodium influx during the depolarization phase of the cardiac action potential, which helps to stabilize the cardiac membrane and reduce the excitability of myocardial cells.

Class I antidysrhythmic medications are further divided into subclasses based on their effects on the cardiac action potential: Class IA, IB, and IC. Each subclass has distinct pharmacological effects and uses in treating various types of arrhythmias, but they all share the common characteristic of sodium channel blockade. By reducing sodium influx, these medications effectively decrease the rate of rapid firing of abnormal electrical impulses in the heart, helping to restore normal rhythm and function.

On the other hand, Class II includes beta-blockers that primarily work by blocking beta-adrenergic receptors, which slows down heart rate but does not directly block sodium channels. Class III antidysrhythmics primarily block potassium channels, therefore prolonging repolarization, while Class IV agents, such as calcium channel blockers, focus on inhibiting calcium channels and have different mechanisms of action compared to sodium channel blockers.