The four classes of antiarrhythmic agents are reviewed, and electrophysiologic effects of selected drugs are discussed. Classification is based on the degree to which an antiarrhythmic agent affects the fast sodium channel, adrenergic response, repolarization of myocardial cells, and the slow calcium channel. Class 1 drugs interfere with the sodium channel and are subgrouped according to the potency of this effect. Class 1A drugs (quinidine, procainamide, disopyramide) prolong refractoriness and have a moderate effect on the sodium channel. Class 1B drugs (lidocaine, phenytoin, tocainide, mexiletine) exert less effect on the sodium channel and tend to shorten rather than prolong refractoriness. Class 1C drugs (encainide, flecainide, lorcainide, and propafenone) have a marked effect on the sodium channel and a minimal effect on repolarization. The β blockers, class 2 drugs, have antiadrenergic properties, and the class 3 drugs (amiodarone, sotalol, bretylium) affect repolarization and markedly prolong refractoriness, action potential duration, and the QT interval. The slow inward calcium current is blocked by class 4 drugs (verapamil, diltiazem). Classification of individual drugs is highly artificial. Despite limitations of the classification scheme, the system provides a useful framework for comparisons among antiarrhythmic agents.
|Original language||English (US)|
|Number of pages||4|
|Issue number||3 II|
|State||Published - Jan 1 1987|
ASJC Scopus subject areas
- Pharmaceutical Science