Medicine & USMLE

Class 3 Antiarrhythmics

Cardio Drugs - Antiarrhythmics
  1. Diltiazem and Verapamil (Calcium Channel Blockers)
  2. Class 1A Antiarrhythmics
  3. Class 1B Antiarrhythmics
  4. Class 1C Antiarrhythmics
  5. Class 3 Antiarrhythmics
  6. Amiodarone Side Effects
  7. Adenosine


Class 3 antiarrhythmics include the drugs amiodarone, dofetilide, ibutilide, and sotalol.

These drugs are potassium channel blockers that prolong repolarization and also prolong the action potential. Sotalol is unique because it is also a beta blocker.

As antiarrhythmics, these medications are used to treat v-tach, ventricular fibrillation, and a-fib.

Side effects include bradycardia, nausea and vomiting, and hypotension. Class 3 antiarrhythmics are known to prolong the QT interval, so the cardiac rhythm should be monitored during treatment.

Key Points

  • Class 3 Antiarrhythmics
    • Drug Names
      • Amiodarone (Pacerone)
      • Sotalol (Betapace, Sorine)
      • Dofetilide (Tikosyn)
      • Ibutilide (Corvert)
    • Mechanism
      • Potassium channel blocker
        • Prolong action potential
          • Lengthens the time it takes for the electrical impulse in the cardiac cell to rise and fall back to its resting state
        • Prolong repolarization
          • Repolarization is the phase when the electrical charge falls back to baseline
      • Beta blocker (sotalol)
        • Sotalol is a non-selective beta adrenergic blocker
    • Clinical Use
      • Ventricular tachycardia
      • Ventricular fibrillation
      • Atrial fibrillation
        • May be effective in converting atrial fibrillation to sinus rhythm
        • Not generally used as first line drug of choice
    • Side Effects
      • Bradycardia
      • Prolongs QT interval
        • Can lead to a life-threatening arrhythmia called torsade de pointes
      • Hypotension
        • Monitor blood pressure during treatment
      • Nausea and vomiting