Pharm 101: Magnesium

Class

Electrolyte

Pharmacodynamics
  • Unclear mechanism, but has been found to have antiarrhythmic effects in some patients with normal serum magnesium levels
  • Recognised to influence Na/K ATPase, Na channels, certain K channels, and Ca channels
Clinical uses
  • Anti-convulsant effect
    • Pre-eclampsia and eclampsia, for prevention and treatment of life-threatening seizures
  • Bronchodilator effect
  • Anti-arrhythmic:
    • Torsades de pointes even if serum magnesium normal
    • Atrial fibrillation
    • Digitalis-induced arrhythmia if hypomagnesaemia present
Toxicity
  • > 4 mmol/L
    • Muscle weakness
    • Hyporeflexia
    • Nausea/vomiting
  • > 10 mmol/L
    • Hypoventilation
    • Arrhythmia
    • Neuromuscular paralysis
    • Coma
Further reading
References
Pharm 101 700

Pharmacology 101

Top 200 drugs

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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