Propranolol

• 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 also increases phase 4 depolarization (heart rate goes up), and increases DAD (delayed afterdepolarizations) and EAD (early afterdepolarization) mediated arrhythmias. These effects are blocked by beta-adrenergic receptor blockers.

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

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

• Adverse effects of beta blocker therapy can lead to fatigue, bronchospasm, depression, impotence, and attenuation of hypoglycemic symptoms in diabetic patients and worsening of congestive heart failure.

Hondeghem, L.M. and Roden, D.M., "Agents Used in Cardiac Arrhythmias", in Basic and Clinical Pharmacology, Katzung, B.G., editor, Appleton & Lange, 1998, pp 216-241

Category: Pharmacology Notes