Vaughan Williams Classification of Anti-arrythmic Drugs

Class	Action	Drugs	Caution
Ia	Sodium channel inhibition: prolong repolarization	Quinidine, procainamide, disopyramide	myocardial infarction, congestive heart failure, renal disease
Ib	Sodium channel inhibition: shorten repolarization	Lidocaine	Proarrhythmias
Ic	Sodium channel inhibition: no effect on repolarization but reduce conductivity	Flecainide, propafenone	Structural heart disease, myocardial infarction, congestive heart failure
II	B-Adrenergic inhibition	Timolol, esmolol, atenolol, bisoprolol	Acute heart failure, bronchospasm
III	Potassium channel inhibition: prolong repolarization	Amiodarone, sotalol	Renal disease, pulmonary disease
IV	Calcium channel inhibition	Verapamil, diltiazem	Not in conjunction with B-blockers
Misc	Na-K ATPase inhibition: potentiate parasympathetic response	Digoxin	Renal disease, hypokalemia