Vaughan Williams antiarrhythmic classification
Dr. E. M. Vaughan William's classification  is the most widely used scheme for antiarrhythmic agents and has stood the test of time. This scheme classifies a drug based on the primary mechanism of its antiarrhythmic effect. Class V is a miscellaneous class, and may be subject to change if a further definite mechanism of anti-arrhythmic action is characterised. Many drugs will have subsidiary actions that are nonetheless important, so sotalol was actually first marketed as a beta-blocker and amiodarone was first developed as a potential anti-anginal vasodilator as it has calcium-channel blocking actions (and every other class except V!)
Class I agents
Class Ia agents block the fast sodium channel which depresses the phase 0 depolarization (reduces Vmax), and prolongs the action potential duration.
Class Ib antiarrhythmic agents are sodium channel blockers that decrease Vmax in partially depolarized cells with fast response action potentials.
Class Ic antiarrhythmics markedly depress the phase 0 depolarization (decreasing Vmax) being the most potent sodium channel blockers.
Class II agents are beta-blockers
They predominantly block the K+ efflux channel.
- ↑ Vaughan Williams EM. Classifying antiarrhythmic actions: by facts or speculation. Journal of clinical pharmacology. 1992 Nov; 32(11):964-77.
- ↑ Vaughan Williams EM. A classification of antiarrhythmic actions reassessed after a decade of new drugs. Journal of clinical pharmacology. 1984 Apr; 24(4):129-47.