**2. History and main uses**

bark and has anti malarial, antipyretic and antiarrhythmic effects. Procainamide and its main metabolite, N-acetyl Procainamide are effective for treating supraventricular and ventricular arrhythmias. Disopyramide has three important side effects. It is vagolytic causing urinary retention, constipation and dry mouth. The class 1b agents are pure sodium channel blockers. This class includes Lidocaine, Phenytoin Mexiletine and Tocainide. Class Ib antiarrhythmic agents used only for the management of ventricular tachyarrhythmia. The class Ic agents are strong sodium channel blockers. This class comprises of Flecainide, Encainide, Propafenone and Moricizine. They are being used to treat ventricular and supraventricular tachyarrhyth‐ mia. They are contraindicated in patients with structural heart disease due to the risk of precipitating life-threatening ventricular arrhythmias. Class II drugs include Metoprolol, Carvedilol, Atenolol, Propranolol and Bisoprolol. They antagonize beta-receptors inhibiting the effect of the sympathetic nervous system resulting in decreased heart rate, contractility and conductivity. The class III agents are drugs that block the potassium channel as their main anti arrhythmic effect. This class includes Sotalol, Dofetilide, Ibutilide, and Amiodarone. They exert their effect by prolonging the refractory period. Sotalol is a nonspecific beta adrenergic receptor blocker with potassium channel blocking properties that is used in managing ventricular arrhythmias and atrial fibrillation. Dofetilide is a potassium channel blocker and excreted by the kidneys. Ibutilide is a short-acting intravenous potassium channel blocker that is used only for the acute termination of atrial fibrillation or flutter. Class IV drugs are Verapamil and Diltiazem. These drugs are known as nondihydropyridine and act by blocking cardiac calcium uptake. They are used to slow AV nodal conduction by decreasing heart rate. Class V agents include Adenosine, Digoxin, magnesium and sulphate are used in supraventricular arrhyth‐ mias, especially heart failure with atrial fibrillation, contraindicated in patients with ventric‐ ular arrhythmias [1–3]. Amiodarone is considered one of the most effective antiarrhythmic drugs which is widely prescribed. Here, its clinical uses as well as its side effects are reviewed.

**Mechanism Examples Class**

AV nodal conduction decreasing heart rate. Verapamil, Diltiazem **IV**

unknown mechanisms Adenosine, Digoxin, magnesium and sulfate **V**

Quinidine, Procainamide, Disopyramide **Ia**

**Ib**

**Ic**

**II**

Lidocaine, Phenytoin, Mexiletine and Tocainide

Flecainide, Encainide, Propafenone and Moricizine

Metoprolol, Carvedilol, Atenolol, Ppropranolol, Bisoprolol

Amiodarone, Sotalol, Dofetilide, Ibutilide, **III**

These drugs block cardiac sodium channels and depress phase 0 of the action potential. Class Ia drugs treat atrial fibrillation and ventricular arrhythmia.

116 Abnormal Heart Rhythms

These drugs are cardiac sodium channel blockers and shorten the action potential. They are used for ventricular tachycardia.

These drugs are cardiac sodium channel blockers. The class Ic drugs are commonly used to treat ventricular and supraventricular tachyarrhythmia.

These drugs are known as beta-blockers and decrease heart rate, contractility and conductivity.

These drugs act by blocking cardiac potassium channels. They are effective to treat atrial fibrillation and ventricular tachycardia.

These are cardiac calcium channel blockers. They are used to slow

**Table 1.** Classification of antiarrhythmic drugs (based on mechanism of action)

Cardiac dysrhythmia also known as arrhythmia or irregular heartbeats is a group of condi‐ tions in which the electrical activity of the heart is irregular [4]. Arrhythmias may occur in the atria or ventricles [5] and is one of the most common signs of anomaly in heart function. Amiodarone as an iodinated benzofuran derivative (Figure 1) is a potent antiarrhythmic drug that is being used for the treatment of a wide variety of cardiac arrhythmias [6]. For the first time, the Russian physiologist, Gleb Von Anrep discovered the original precursor molecule of Amiodarone that was called Khellin. Khellin is the extract of an African plant named Khella. Anrep noticed that one of his technicians' angina symptom was cured after he took Khellin [7, 8]. In 1960, European pharmaceutical industries were working on the preparations of extracts derived from Khellin and finally they purified and developed Amiodarone in1961 [7]. Oral Amiodarone that suppresses life-threatening ventricular arrhythmias and also chronic atrial fibrillation is available in tablets of 200 mg and 400 mg in generic forms as Cardarone and Pacerone, respectively. In addition to the tablet forms, it is also available in solution for intravenous administration. Intravenous administration of Amiodarone is effective in suppress‐ ing serious arrhythmias which reduces the need for atrial fibrillation cardiac surgeries. The intravenous administration of Amiodarone requires following a restrict dosing schedule. Amiodarone is typically given in high doses of 800-1600 mg daily, either intravenously or orally until the arrhythmia is under control, although for long-term oral administration of the drug 200 - 600 mg daily is recommended [8–10].
