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 (UWA) CCPU Emergency Medicine Trainee with interests in medical education, ECG interpretation, and the use of point-of-care ultrasound in the undifferentiated patient. Co-author of the LITFL ECG Library | Twitter

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