Magnesium Sulfate
Classification
Electrolyte
Indications
ACP: Treatment of Torsades de Pointes
ACP: Bronchospasm refractory to bronchodilation in acute asthma exacerbation
ACP: Management of seizures in pregnancy associated with hypertension
Contraindications
Contraindication
- Hypersensitivity to magnesium sulfate
- Second or third-degree AV block
Caution
- Hypotension
- Concurrent use of neuromuscular blockade
- Myasthensia gravis
Adult dosages
ACP: Torsades de Pointes/Polymorphic VT Refer to WCT
- For perfusing rhythms (stable): 2 g IV over 15 minutes
- In cardiac arrest: 2 g IV push over 1-2 minutes
ACP: Bronchospasm refractory to bronchodilation
- 2 g IV over 15 minutes
ACP: Prophylaxis of seizures in pregnancy associated with hypertension. Refer to Preeclampsia
- ☎️ CliniCall consultation required prior to administration to discuss treatment plan.
- Cardiac monitoring is required
- Administer 5 g intravenously over 15 minutes
- Can give 5 g intramuscularly if unable to start IV (use bilateral buttocks)
ACP: Prevention of recurrent seizures in pregnancy associated with hypertension. Refer to Eclampsia
- Cardiac monitoring is required
- Administer 5 g intravenously over 15 minutes followed by 1 g/hour
- Can give 5 g intramuscularly if unable to start IV (use bilateral buttocks) followed by 5 g IM every 4 hours
If seizures persist greater than 5 minutes contact EPOS for further care options.
Pediatric Considerations And Dosing
ACP: Torsades de Pointes/polymorphic VT
- For perfusing rhythms(stable): 50 mg/kg IV/IO (maximm 2 g) over 15 minutes
- In cardiac arrest 50 mg/kg IV/IO (maximum 2 g) IV push over 1-2 minutes
ACP: Bronchospasm
- Severe asthma refractory to bronchodilator: 50 mg/kg IV/IO (maximum 2 g) over 15 minutes
Preparation and Administration
Infusion
Adult and pediatric standard concentration
- 2g in 50mL NS
- 5g in 50mL NS
Mechanism Of Action
The precise mechanism of action of magnesium sulfate is not entirely clear. It appears to alter membrane potential, slowing conduction and relaxing smooth muscle.
Pharmacokinetics
Intravenous:
- Onset: 1-2 minutes
- Peak: < 5 minutes
- Duration: 30 minutes as anticonvulsant
Infusions may take up to 20-30 minutes to produce significant bronchodilation
Adverse Effects
- Hypotension
- Heart block
- Drowsiness
- Respiratory depression
- Arrhythmias
Overdose
Calcium chloride should be available for magnesium sulphate overdose.
Warning And Precautions
May prolong the effects of non-depolarizing neuromuscular blockers and may potentiate the effects of calcium channel blockers.