Class III Antiarrythmics - Sotalol



Sotalol is Class III antiarrhythmic medication that works by blocking potassium channels in cardiomyocytes, which increases the refractory period. Sotalol primarily targets arrhythmias in non-nodal cardiac myocytes, which makes it good for rhythm control. Sotalol is also a beta blocker, and has mild class II antiarrhythmic properties. A dangerous side effect of sotalol and all class 3 antiarrhythmics is QT prolongation leading to Torsades de pointes.

Key Points

  • Sotalol
    • Mechanism
      • Acts as Class 2 and 3 Antiarrhythmic
        • Causes Beta-blocker Activity
          • Reduces cAMP and calcium influx at nodal tissue
          • Slows down heart rate, AV conduction (PR interval)
        • Blocks Potassium (K+) channels
          • Prolongs phase 3 repolarization by blocking potassium outflow, mainly in non-nodal tissue
          • Increases AP duration and effective refractory period (ERP)
            • Prolonged QT creates risk for early after-depolarizations and Torsades de Pointes
    • Clinical Use
      • Treats Atrial flutter/fibrillation
      • Treats Ventricular tachycardia
    • Adverse Effects
      • Causes Long QT (Torsades de Pointes risk)
        • All drugs that increase QT interval increase the risk of early after-depolarizations causing ventricular arrhythmias like Torsades de Pointes
        • Avoid in patients with congenital or acquired long QT syndrome