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Magnesium Sulfate

Classification

Antiarrhythmic

Smooth muscle relaxant

Indications

ACP: Treatment of ventricular fibrillation and ventricular tachycardia refractory to first-line antiarrhythmics

ACP: Recurrent, intermittent episodes of wide-complex tachycardia

ACP: Treatment of Torsades de Pointes

ACP: Bronchospasm refractory to bronchodilation in acute asthma

ACP: Management of seizures in pregnancy associated with hypertension

Contraindications

Hypersensitivity to magnesium sulfate
Second or third-degree AV block

Adult dosages

ACP: Control of ventricular arrhythmias (including Torsades de Pointes)

CliniCall consultation required prior to administration of magnesium sulfate.
For perfusing rhythms: 2 g IV over 15 minutes
In cardiac arrest: 4 g IV push

ACP: Bronchospasm refractory to bronchodilation

2 g IV over 20 minutes

ACP: Management of seizures in pregnancy associated with hypertension

CliniCall consultation recommended to discuss care planning options
Cardiac monitoring is required with magnesium administration
Administer the initial dose of 4-6 g intravenously over 20 minutes as a loading dose followed by 1-2 g per hour; otherwise, 5 g can be given intramuscularly (use bilateral buttocks) followed by 5 g IM every four hours
If seizures persist following the loading dose of magnesium, up to 4 g IV can be given over five minutes

Pediatric Considerations And Dosing

Follow weight-based dosing

ACP: All indications

In cardiac arrest: 50 mg/kg IV/IO push to maximum of 2 g
All other causes: 50 mg/kg IV/IO infused over 15 minutes

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

Warning And Precautions

May prolong the effects of non-depolarizing neuromuscular blockers and may potentiate the effects of calcium channel blockers.