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Propranolol [proe pran' oh lol]
(Class II, Beta-Adrenergic Receptor Blocker)

  • Antiarrhythmic effects are due mainly to beta-adrenergic receptor blockade. Normally, sympathetic drive results in increased in Ca2+ ,K+ ,and Cl- currents.

  • Increased sympathetic tone:

    • Increases phase 4 depolarization (heart rate goes up), and

    • Increases DAD (delayed afterdepolarizations) and EAD (early afterdepolarization) mediated arrhythmias. These effects are blocked by β-adrenergic receptor blockers.

  • β-adrenergic receptor blockers increase AV conduction time and increase AV nodal refractoriness, thereby helping to terminate nodal reentrant arrhythmias.

  • β-adrenergic receptor blockade can also help reduce ventricular following rates in atrial flutter and fibrillation, by acting at the AV node.

Adverse effects of β-blocker therapy can lead to:

  • Fatigue,

  • Bronchospasm,

  • Depression,

  • Impotence,

  • Attenuation of hypoglycemic symptoms in diabetic patients and

  • Worsening of congestive heart failure.

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