Mg2+ is a cation that is important for neurotransmission and neuromuscular excitability. Magnesium:

  • Inhibits ACh release at the NMJ
  • Acts a cofactor in multiple enzyme systems
  • Is important in the production of:
Property Action
Uses HypoMg, arrhythmia, eclampsia, tocolysis, barium poisoning, asthma, tetanus, autonomic hyperreflexia
Presentation, made up into 10mmol in 100ml for peripheral administration
Route of Administration PO/IV
Dosing IV: 10-20 mmol
Distribution 30% protein bound
Elimination Significant urinary excretion, even when deficient
Resp Bronchodilation
CVS SVR, hypotension, ↓HR
CNS CNS depression, anticonvulsant
GU ↓ Uterine tone and contractility

Clinical Effects of Magnesium

[Plasma] Effect
< 0.7 mmol.L-1 Arrhythmia
4-6 mmol.L-1 Nausea, hyporeflexia, speech impairment
6-10 mmol.L-1 Weakness, respiratory depression, bradycardia
> 10 mmol.L-1 Cardiac arrest


  1. Smith S, Scarth E, Sasada M. Drugs in Anaesthesia and Intensive Care. 4th Ed. Oxford University Press. 2011.
  2. Peck TE, Hill SA. Pharmacology for Anaesthesia and Intensive Care. 4th Ed. Cambridge University Press. 2014.
  3. Rang HP, Dale MM, Ritter JM, Flower RJ. Rang and Dale's Pharmacology. 6th Ed. Churchill Livingstone.
Last updated 2017-09-20

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