Which drug is an example of Class 4 in the Vaughan Williams classification?

In the Vaughan Williams classification of antiarrhythmic drugs, Class 4 agents are calcium channel blockers. These medications are primarily used to manage arrhythmias by slowing down conduction through the AV node and reducing heart rate. Diltiazem is indeed a representative of this class, as it is a well-known calcium channel blocker that exerts effects on cardiac conduction and is often utilized to treat conditions such as atrial fibrillation and atrial flutter.

In contrast, the other drugs listed fall into different classes. Dofetilide is classified as a Class 3 antiarrhythmic, which primarily works by inhibiting potassium channels and prolonging the action potential duration. Digoxin, while used for heart conditions, is classified as a cardiac glycoside rather than an antiarrhythmic drug in the Vaughan Williams classification. Flecainide is a Class 1c antiarrhythmic, which works by blocking sodium channels.

Thus, the categorization of diltiazem as a Class 4 drug aligns correctly with its mechanism of action and therapeutic application in managing arrhythmias.