Antiarrhythmic drugs are used to treat arrhythmias, disturbancesof the normal heart rhythm.Unfortunately, many antiarrhythmics are also capable of worsen-ing or causing the very arrhythmias they’re supposed to treat. The benefits need to be weighed carefully against the risks of antiar-rhythmic therapy.
Antiarrhythmics are categorized into four classes:
· I (which includes classes IA, IB, and IC)
Class I antiarrhythmics consist of sodium channel blockers. This is the largest group of antiarrhythmics. Class I agents are fre-quently subdivided into classes IA, IB, and IC. One drug, adeno-sine (an AV nodal blocking agent used to treat paroxysmal supra-ventricular tachycardia), doesn’t fall into any of these classes.
The mechanisms of action of antiarrhythmics vary widely, and a few drugs exhibit properties common to more than one class.