Parenteral Manual

Magnesium sulfate

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Alternate Name(s): 
Magnesium sulfate
Electrolyte, Anticonvulsant
Original Date: 
August 2005
Revised Date: 
December 2019
  • Magnesium replacement
  • Treatment of seizures and encephalopathy associated with acute nephritis
  • Treatment of hypertension
  • Treatment of torsade de pointes
  • Adjunctive treatment for bronchodilation in moderate to severe asthma (unlabelled use)
  • Treatment of chronic pain/migraine
Reconstitution and Stability: 
  • Premixed SYRINGE of magnesium sulfate 40 mg/mL
     Available from Pharmacy, ED Resus or PICU
    Administer via SYRINGE PUMP

  • Premixed IV BAG for Oncology:  2 to 4 mmol Magnesium sulfate/L ( equals 500 to 1000 mg Magnesium/L) 
    Prepared by pharmacy
     Administer via LARGE VOLUME PUMP




- Solutions Compatible: dextrose up to D10W ,0.9% NaCl, dextrose-saline combinations, ringer's solution, ringer's lactate

- Additives/Above Cassette Compatible: KCl

- Y-site Compatible: cefazolin, cefotaxime, dobutamine, heparin, KCl, morphine, TPN (amino acids/dextrose), vancomycin

- Incompatible:  furosemide, sodium bicarbonate


(For approved routes of administration by nursing personnel, refer to Policy for the Administration of Intravenous Medications.)


YES -only if IV access is impossible

IV Intermittent

Critical care areas & ED only


YES   -SYRINGE PUMP -respiratory support, cardiac monitoring
Usual dilution: 40 mg/mL of magnesium sulfate/mL

Infusion rate: do not exceed 150 mg magnesium sulfate/minute

Infusion time: 15-30 minutes

Infusion time: 30 - 45 minutes

IV Intermittent Infusion

Usual dilution: 40 mg/mL of magnesium sulfate

Infusion time:  for hypomagnesemia: 2-4 hours; In severe circumstances, half of dose administered over the first 15-30 minutes
for MDU chronic pain/migraine: 30 minutes

for ED/PICU asthma: 20 - 30 minutes
Infusion rate: do not exceed 125 mg magnesium sulfate/kg/hour

IV Continuous Infusion


Usual Dilution: 0.16 mmol/mL (magnesium sulfate 40 mg/mL)

Infusion time: Max rate of 0.25 mL/kg/hour


Usual Dilution:  2 to 4 mmol magnesium /L of IV solution



(For neonatal dosages, refer to Neonatal IV Drug Manual.)


-Management of seizures:

Use Premixed SYRINGE of magnesium sulfate 40 mg/mL

Available from Pharmacy, ED resus or PICU

Administer via SYRINGE pump


Dose: 20 to 100 mg magnesium sulfate /kg/dose IV Q4-6H PRN

May use up to 200 mg magnesium sulfate/kg/dose


-Broncholidation, as adjunctive therapy

Use Premixed SYRINGE of magnesium sulfate 40 mg/mL

Available from Pharmacy, ED resus or PICU

Administer via SYRINGE pump


Dose: 25 to 50 mg magnesium sulfate /kg/dose IV x 1 dose

Maximum single dose: 2000 mg magnesium sulfate

A few reports in literature describe administration of a second dose in 4 - 6 hours if clinically necessary

- Hypomagnesemia in PICU
Use Premixed SYRINGE of magnesium sulfate 40 mg/mL

Available from Pharmacy, ED resus or PICU

Administer via SYRINGE pump


Dose: 25 to 50 mg/kg/dose IV Q4-6H x 3-4 doses

Higher doses up to 100 mg/kg/dose have been used

Maximum single dose: 2000 mg magnesium sulfate


- Hypomagnesemia associated with hypocalcemia

Dose: 10 mg/kg/hour IV (MAX 500 mg/hr) x 4 hours (then reasses)

-Prevention/Treatment of cisplatin-induced hypomagnesemia in Oncology

Use IV solution prepared by Pharmacy (2 to 4 mmol Magnesium/L of IV solution)


- Hypomagnesemia:       

  • 1000 mg magnesium sulfate IM/IV Q 6 hours x 4 doses
  • Maximum single dose: 2000 mg magnesium sulfate

- Management of seizures:  1000 mg magnesium sulfate IM/IV Q 6 hours PRN

- Bronchodilation: 2000 mg magnesium sulfate as a single dose

PRE and POST Oxaliplatin for patient over 40 kg:
Magnesium sulfate 1000 mg and Calcium gluconate 1000 mg in 250 mL D5W over 30 minutes

Potential hazards of parenteral administration: 

- Adverse effects are often related to the magnesium serum levels:

  • CNS depression
  • Hypotension
  • Muscle weakness
  • Flushing of skin, somnolence, sweating
  • Depressed deep tendon reflexes (patellar reflex) at magnesium serum concentrations > 10 mmol/L and absent at 20 mmol/L
  • Respiratory depression and complete heart block may occur at magnesium levels greater than 20 mmol/L
  • NOTE:  magnesium toxicity is exacerbated by hypocalcemia
  • Spot team is activated to assess patient with severe asthma requiring Magnesium Sulfate
    and is allowed to order and administer on the ward with proper cardiorespiratory monitoring
  • Monitor urine output.  During infusion, monitor for cardiac dysrhythmias, hypotension, respiratory and CNS depression
  • Serum magnesium levels recommended if dosing is prolonged, continuous infusion is employed or in patients with renal failure
  • Hypomagnesemia may contribute to the development of digoxin toxicity.  However, supplementation with magnesium should be carried out slowly (over several days) because magnesium re-equilibrates slowly and because hypermagnesemia may cause arrhythmias and alter cardiac conduction, leading to heart block
  • Contraindicated in: heart block, serious renal impairment
  • Antidote for respiratory depression is calcium chloride or calcium gluconate
  • IV onset: immediate (as an anticonvulsant)
  • IV duration: 30 minutes (as an anticonvulsant)

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