Pharm 101: Propranolol

Class

Beta-blocker
Class II antiarrhythmic

Pharmacodynamics

• Competitive non-selective beta-blocker
• Direct membrane effects (Na channel blockade) and prolongation of action potential duration
• Cardiovascular effects:
  • Negative inotrope, negative chronotrope: reduces blood pressure primarily due to reduced cardiac output
  • Increased PR interval: increases AV nodal refractory period
  • Antagonises renin release from sympathetic nervous system: inhibits stimulation of renin production by catecholamines (mediated by beta-1 receptors)
• Respiratory:
  • Bronchospasm
• Opthalmological:
  • Decreased intra-ocular pressure
• Metabolic:
  • Decreased glycogenolysis

Pharmacokinetics

• 25% bioavailability
• Highly lipid soluble
• Half-life 3-5 hours

Clinical uses

• Supraventricular arrhythmias
• Thyrotoxicosis to control severe cardiovascular manifestations
• Migraine prophylaxis (reduces frequency and intensity of migraines)

Adverse effects

• Bradycardia
• AV blockade
• Hypotension
• Bronchospasm
• Reduced hypoglycaemia response
• Toxicity:
  • In high doses has Na channel blocking effects similiar to TCAs
  • Seizures and cardiac conduction block

Further Reading

• Nickson C. Propranolol Overdose