Medicine & USMLE


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


Amiodarone is a class III antiarrhythmic drug used to treat ventricular arrhythmias, specifically ventricular fibrillation and ventricular tachycardia. Amiodarone is most commonly used as part of ACLS protocol, but may be prescribed for patients with atrial fibrillation and a history of ventricular arrhythmias to take at home. Important side effects of amiodarone include pulmonary toxicity, QT prolongation, and hypothyroidism.

Key Points

  • Mechanism
    • Antiarrhythmic
      • Class III
      • Blocks potassium channels causing prolonged repolarization of the cardiac action potential. This slows down the heart rate, decreases peripheral vascular resistance, and causes vasodilation
    • Clinical Use
      • Arrhythmias
        • Ventricular arrhythmias
          • Ventricular tachycardia
            • Part of ACLS protocol
          • Ventricular fibrillation
            • Also part of ACLS protocol
          • Supraventricular tachycardia (SVT)
            • Off-label use
        • Atrial fibrillation
          • Common off-label use
          • Particularly atrial fibrillation with a rapid ventricular rate
    • SE and AR
      • Pulmonary toxicity
        • Dyspnea, cough, chest pain, rales/crackles
        • Can be fatal
      • QT interval prolongation
        • Can lead to Torsades de Pointes
        • Requires close cardiac monitoring in hospital setting
      • Hypothyroidism
        • Amiodarone has high iodine content, which directly affects the thyroid
      • Hypotension
      • Bradycardia
        • Teach patient to monitor pulse at home
      • Visual disturbances
        • Secondary to corneal microdeposits
        • Photophobia, visual halos
      • Dermatological effects
        • Photosensitivity
        • Blue man syndrome
          • A blue/gray discoloration of the skin
          • An uncommon adverse effect that may present with long-time use
      • Hepatotoxicity
        • May increase ALT and AST
      • Teratogenic
        • Pregnancy Risk Category D