Antiarrhythmics are drugs that are used to treat abnormal heart rhythms resulting from irregular electrical activity of the heart. Antiarrhythmics includes class IA, class IB, class IC, class II, class III, class IV, and miscellaneous. These drugs are used to treat and prevent cardiac arrhythmias of various etiologies. Class IA includes disopyramide, moricizine, procainamide, and quinidine sulfate. Class IB includes lidocaine, mexiletine, and phenytoin. Class IC includes flecainide, and propafenone. Class II includes esmolol, propranolol, and sotalol. Uses, dosages, and side effects of antiarrhythmics drug are also discussed in this chapter.