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
Pharm 101 700

Pharmacology 101

Top 200 drugs

MBBS CCPU (RCE, Biliary, DVT, E-FAST, AAA) Rob is an Emergency Medicine Advanced Trainee based in Melbourne, Australia. He has special interests in medical education, ECG interpretation, and the use of diagnostic and procedural ultrasound in the undifferentiated and unwell patient.

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