Magnesium Sulfate


  • Nervous System


  • Antiarrhythmic, uterine relaxant, electrolyte supplement


  • Hypomagnesemia

  • Eclampsia prophylaxis

  • Preterm labor (non FDA approved)


  • Renal failure, hypermagnesemia; appendicitis, bowel obstruction/perforation

  • Patients with heart block or myocardial damage


  • Pregnancy category B

  • Diarrhea, digitalized patients, impaired renal function

Adverse Reactions (Side Effects):

  • CNS: coma, depressed deep tendon reflexes, lethargy, weakness

  • CV: decreased BP, heart block, increased pulse

  • METAB: hypermagnesemia

  • RESP: respiratory distress


Administered parenterally

  • Adult:  

    • IM 4-5g of 50% solution every 4 hours as needed

    • IV 4g of a 10%-20% solution initially then 4-5g in 250ml of D5W or NS at a rate not exceeding 3 ml/min by infusion (pre-eclampsia)

    • IM/IV 1g every 6 hours for 4 doses; for severe deficiency, 8-12g daily in divided doses (hypomagnesemia); PO 10-15g in a glass of water (laxative)

  • Child: 

    • Neonate IV 25-50 mg/kg/dose every 8-12 hours for 2-3 doses

    • child 

      • IM/IV 25-50 mg/kg/dose every 4-6 hours for 3-4 doses, max single dose 2000mg (hypomagnesemia); 

      • PO 5-10g in a glass of water (laxative)

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