Classification of Antiarrhythmic Drugs
| Class | Drugs | Action |
| Ia | Quinidine, Procainamide, Disopyramide | Block fast sodium current. These also block repolarising potassium currents and hence lengthen action potential duration |
| Ib | Lignocaine, Mexiletine, Phenytoin | Block fast sodium current. This slows rate of depolarisation and reduces conduction velocity. These shorten action potential duration |
| Ic | Flecainide, Encainide | Block fast sodium current with slow offset kinetics. Cause marked depression of depolarisation with little change in action potential duration. |
| II | Beta-Blockers | Block effects of catecholamines |
| III | Amiodarone, Sotalol | Lengthen action potential duration by blocking potassium currents |
| IV | Calcium channel blockers | Block inward calcium current particularly notable in AV node |