Antiarrhythmic Classification

Class I

Fast sodium (Na) channel blockers

Ia – Quinidine, procainamide, disopyramide (depress phase 0, prolonging repolarization)

Ib – Lidocaine, phenytoin, mexiletine (depress phase 0 selectively in abnormal/ischemic tissue,
shorten repolarization)

Ic – Flecainide, propafenone, moricizine (markedly depress phase 0, minimal effect on repolarization)

Class II

  • Propranolol (decreases slope of phase 4)
  • Esmolol (decreases slope of phase 4)
  • Timolol (decreases slope of phase 4)
  • Metoprolol (decreases slope of phase 4)
  • Atenolol (decreases slope of phase 4)

Class III

Potassium(K) channel blockers
  • Amiodarone (prolongs phase 3; also acts on phases 1, 2, and 4)
  • Sotalol (prolongs phase 3, decreases slope of phase 4)
  • Ibutilide (prolongs phase 3)
  • Dofetilide (prolongs phase 3)

Class IV

Slow calcium (Ca) channel blockers
  • Verapamil (prolongs phase 2)
  • Diltiazem (prolongs phase 2)

Class V

Variable mechanism
  • Adenosine
  • Digoxin
  • Magnesium sulfate

Emergency Medicine

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