Which medication is classified under Class 3 of the Vaughan Williams classification?

Amiodarone is classified under Class 3 of the Vaughan Williams classification. This classification system categorizes antiarrhythmic drugs based on their primary electrophysiological effect on the cardiac action potential. Class 3 agents are primarily potassium channel blockers, which prolong repolarization and the refractory period of the cardiac action potential, thus helping to manage various types of arrhythmias.

Amiodarone, in particular, is known for its effectiveness in treating atrial fibrillation and ventricular tachycardia. It works by blocking potassium channels, leading to a prolongation of the QT interval and an increased refractory period. This mechanism helps to stabilize heart rhythm and prevent the recurrence of arrhythmias.

In contrast, the other medications listed do not fall under Class 3. Verapamil is a Class 4 agent, which affects calcium channels and helps to reduce heart rate and contractility. Rivaroxaban is an anticoagulant that does not fit into the Vaughan Williams classification at all as it is not an antiarrhythmic drug. Quinidine belongs to Class 1A, as it is a sodium channel blocker that also prolongs the repolarization period but does it primarily through sodium channel interference rather than potassium channel blockage