question: Which are the classes of anti-arrhythmic drugs according to Vaughan-Williams classification?
answer: Antiarrhythmic drugs can be divided into four Vaughan Williams classes (I-IV). Class I antiarrhythmic agents have as a common action, blockade of the sodium channels. Class II agents are antisympathetic drugs, particularly the beta-adrenoceptor blockers. Class-III antiarrhythmics have as a common action the potassium-channel blockade. Class IV antiarrhythmic drugs are calcium channel blockers.