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 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.

Follow him on twitter: @rob_buttner | ECG Library |

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