Which class of drugs is known as Vaughan-Williams Class III?

Vaughan-Williams Class III refers specifically to medications that primarily work by blocking potassium channels, leading to the prolongation of the action potential and refractory period in cardiac tissue. This mechanism is crucial for the management of various arrhythmias, including atrial fibrillation and ventricular tachycardia, as it helps to stabilize the cardiac rhythm and prevent abnormal heartbeats.

Common examples of Class III antiarrhythmic drugs include amiodarone, sotalol, and dofetilide. These medications have been shown to be effective in both acute and chronic settings for treating life-threatening arrhythmias.

In contrast, the other classes mentioned serve different primary purposes: beta blockers primarily reduce heart rate and myocardial oxygen demand by blocking beta-adrenergic receptors, sodium channel blockers work by inhibiting sodium influx during depolarization (affecting phase 0 of the action potential), and calcium channel blockers mainly reduce myocardial contractility and can also affect heart rate by inhibiting calcium entry into cardiac and smooth muscle cells. Each of these drug classes plays unique roles in cardiovascular pharmacotherapy but does not fit the definition of Class III antiarrhythmics.