Anti-Arrhythmic Agents

Singh Vaughan Williams classification of antiarrhythmic agents

1.       Class I agents interfere with the sodium (Na⁺) channel.

2.       Class II agents are anti-sympathetic nervous system agents.

Most agents in this class are beta blockers.

3.       Class III agents affect potassium (K⁺) efflux.

4.       Class IV agents affect calcium channels and the AV node.

5.       Class V agents work by other or unknown mechanisms.

Class	Known as	Examples	Mechanism
Ia	Na+ channel blockers	Quinidine Procainamide Disopyramide	(Na+) channel block (intermediate association/dissociation)
Ib		Lidocaine Phenytoin Mexiletine	(Na+) channel block (fast association/dissociation)
Ic		Flecainide Propafenone Moricizine	(Na+) channel block (slow association/dissociation)
II	Beta-blockers	Propranolol Esmolol Timolol Metoprolol Atenolol Bisoprolol	beta blocking Propranolol also shows some class I action
III	K+ channel blockers	Amiodarone Sotalol Ibutilide Dofetilide E-4031	K+ channel blocker Sotalol is also a beta blocker[2]
IV	L-type Ca2+ channel blockers	Verapamil Diltiazem	Ca2+ channel blocker
V	Miscellaneous	Adenosine Digoxin	Work by other or unknown mechanisms (Direct nodal inhibition).