Pharm 101: Metoprolol

Class

Beta-Blocker

Pharmacodynamics

• Along with bisoprolol, atenolol, nebivolol, esmolol, act via selective B1-receptor blockade
  • Equally selective to B1 blockade as propranolol
  • However, 50-100x less potent than propranolol in blocking B2-receptors
  • At higher doses, metoprolol is less selective in blockade
• Cardiovascular effects:
  • Negative inotrope and chronotrope
  • Slows AV conduction (prolongs PR interval)
  • Suppresses renin release mediated via beta-receptors through catecholamines (decreases blood pressure)

Pharmacokinetics

• PO or IV administration
• Well absorbed orally but bioavailability 50% due to high first pas metabolism
• Hepatic metabolism
• Large volume of distribution (> 200L)
• Moderate lipid solubility
• Half-life 3-4 hours

Clinical uses

• Hypertension
• IHD (reduced frequency of anginal episodes and improved exercise tolerance)
• Improved survival after MI
• Arrhythmias: AF / flutter
• CCF

Adverse effects

• Bradycardia
• Hypotension
• Bronchoconstriction (although less common with selective B1-blockade)
• Vivid dreams

Further Reading

• Nickson C. Beta-Blocker Overdose
• Richards J. Beta-Blockers for Cocaine and other Stimulant Toxicity