| Indication | For the maintenance of normal sinus rhythm [delay in time to recurrence of atrial fibrillation/atrial flutter (AFIB/AFL)] in patients with symptomatic AFIB/AFL who are currently in sinus rhythm. Also for the treatment of documented life-threatening ventricular arrhythmias. |
| Pharmacodynamics | Sotalol is an antiarrhythmic drug. It falls into the class of beta blockers (and class II antiarrhythmic agents) because of its primary action on the β-adrenergic receptors in the heart. In addition to its actions on the beta receptors in the heart, sotalol inhibits the inward potassium ion channels of the heart. In so doing, sotalol prolongs repolarization, therefore lengthening the QT interval and decreasing automaticity. It also slows atrioventricular (AV) nodal conduction. Because of these actions on the cardiac action potential, it is also considered a class III antiarrhythmic agent. The beta-blocking effect of sotalol is non-cardioselective, half maximal at about 80mg/day and maximal at doses between 320 and 640 mg/day. Sotalol does not have partial agonist or membrane stabilizing activity. Although significant beta-blockade occurs at oral doses as low as 25 mg, significant Class Ieffects are seen only at daily doses of 160 mg and above. |
| Mechanism of action | Sotalol has both beta-adrenoreceptor blocking (Vaughan Williams Class I) and cardiac action potential duration prolongation (Vaughan Williams Class I) antiarrhythmic properties. Sotalol is a racemic mixture of d- and l-sotalol. Both isomers have similar Class I antiarrhythmic effects, while the l-isomer is responsible for virtually all of the beta-blocking activity. Sotalol inhibits response to adrenergic stimuli by competitively blocking β1-adrenergic receptors within the myocardium and β2-adrenergic receptors within bronchial and vascular smooth muscle. The electrophysiologic effects of sotalol may be due to its selective inhibition of the rapidly activating component of the potassium channel involved in the repolarization of cardiac cells. The class II electrophysiologic effects are caused by an increase in sinus cycle length (slowed heart rate), decreased AV nodal conduction, and increased AV nodal refractoriness, while the class III electrophysiological effects include prolongation of the atrial and ventricular monophasic action potentials, and effective refractory period prolongation of atrial muscle, ventricular muscle, and atrio-ventricular accessory pathways (where present) in both the anterograde and retrograde directions. |
| Absorption | In healthy subjects, the oral bioavailability of sotalol is 90-100%. Absorption is reduced by approximately 20% compared to fasting when administered with a standard meal. |
| Volume of distribution | Not Available |
| Protein binding | Sotalol does not bind to plasma proteins. |
| Metabolism | Sotalol is not metabolized. |
| Route of elimination | Excretion is predominantly via the kidney in the unchanged form. Sotalol is excreted in the milk of laboratory animals and has been reported to be present in human milk. |
| Half life | Mean elimination half-life is 12 hours. Impaired renal function in geriatric patients can increase the terminal elimination half-life. |
| Clearance | Not Available |
| Toxicity | The most common signs to be expected are bradycardia, congestive heart failure, hypotension, bronchospasm and hypoglycemia. In cases of massive intentional overdosage (2-16 grams) of sotalol the following clinical findings were seen: hypotension, bradycardia, cardiac asystole, prolongation of QT interval, Torsade de Pointes, ventricular tachy-cardia, and premature ventricular complexes. |