Magnesium sulfate
See critical care quick reference for drug doses by weight.
General
- Type: Antiarrhythmics
- Dosage Forms: IV
- Common Trade Names: None
Adult Dosing
Cardiac arrest
- Loading dose = 1-2gm in 10mL D5W over 1-2min
Spontaneous circulation
- Loading dose = 1-4gm in 50-100 D5W over 20-60 min
Eclampsia
- Initial: 4-6 g IV magnesium sulfate (Dilute the 50% solution of 400mg elemental magnesium, to a 10% or 20% solution) and give over 20 to 30 minutes
- Maintenance: 1 to 2 g/hr IV until paroxysms cease
OR
- If no IV Access, give Magnesium sulfate 50% solution IM 10g Loading Dose (5g in each buttock)
- Maintenance: followed by 5 g IM q 4 hours
(Note: Use IM if no IV, No data on IO Route for Ecclampsia)
Pediatric Dosing
- Torsades: 25 to 50mg/kg rapid infusion over several minutes
Cardiac
- 25-50mg/kg IV x 1
See critical care quick reference for drug doses by weight.
Special Populations
- Pregnancy Rating: D (despite being drug of choice for eclampsia!)
- Lactation: infant risk minimal
- Renal Dosing: for severe renal impairment, max dose 20g/48 hours
- Adult
- Pediatric
- Hepatic Dosing
- Adult
- Pediatric
Indications
- QT prolongation
- Torsades
- Refractory v-tach/fib (regardless of Mg level)
- Eclampsia
- Hypomagnesemia
- Barium poisoning
Contraindications
- Allergy to class/drug
Adverse Reactions
Serious
- Hypotension (rare)
- Heart block
- CNS depression
- Respiratory depression
Common
Pharmacology
- Half-life:
- Onset of action = Immediate
- Duration of action = 30min
- Metabolism:
- Excretion: Renal
Mechanism of Action
- Increases vasomotor tone
- Prolongs AV conduction; prolongs refractoriness
Indications by Condition
The following table is automatically generated from disease/condition pages across WikEM.
| Indication | Dose | Context | Route | Population |
|---|---|---|---|---|
| Acute asthma exacerbation | 25-75 mg/kg IV over 30 min (2-3 g in most adults) | Adjunct for moderate-severe asthma | IV | Adult |
| Acute asthma exacerbation | 50 mg/kg/hr IV x4 hours (max 8000 mg total) | High-dose magnesium (pediatric) | IV drip | Pediatric |
| Acute asthma exacerbation (peds) | 25-50mg/kg (max 2g) IV over 20min | Severe/refractory asthma; smooth muscle relaxation | IV | Pediatric |
| Aluminum phosphide poisoning | 4g IV over 20min, then 6g over 12hr infusion | Cardioprotective, may reduce mortality | IV | Adult |
| Antipsychotic toxicity | 2-4g IV over 10 min | QTc >500ms | IV | Adult |
| Atrial fibrillation with RVR | 2g over 1-5min; repeat after 15min if no response; then 1-2g/hr x 4hr | Adjunctive rate control | IV | Adult |
| Cesium toxicity | 2g IV bolus | First-line for QTc prolongation | IV | Adult |
| Electrical storm | 1-2g IV over 1-2 min | Torsades with known long QT | IV | Adult |
| Headache | 1-2 g IV over 30-60 min | 2nd/3rd line for acute headache | IV | Adult |
| Hydrogen fluoride toxicity | 4g IV over 20 min | Replete magnesium | IV | Adult |
| Hypomagnesemia | 4g | Serum Mg <1.2 | IV | Adult |
| Hypomagnesemia | 2g | Serum Mg 1.2-1.7 (symptomatic or no POs) | IV | Adult |
| Migraine headache | 1-2 g IV over 15-30 min | Adjunct (especially for aura) | IV | Adult |
| Migraine headache | 1-2 g IV over 30-60 min | 2nd/3rd line for acute headache | IV | Adult |
| Polymorphic ventricular tachycardia | 1-2g IV, repeat in 5-15min; then 1-2g/hr infusion | Torsades de pointes | IV | Adult |
| Polymorphic ventricular tachycardia | 25-50mg/kg (max 2g) IV | Torsades de pointes | IV | Pediatric |
| Preterm labor | 4-6g IV load over 20-30min, then 2g/hr infusion | Fetal neuroprotection if <32 weeks | IV | Adult |
| Pulseless arrest | 2 g, followed by maintenance infusion | Polymorphic VT | IV | Adult |
| Selective serotonin reuptake inhibitor toxicity | 2g IV | QTc >500 msec (citalopram/escitalopram) | IV | Adult |
| Torsades de pointes | 1-2g IV over 1-2 min, repeat in 5-15min; then 1-2g/hr drip | First-line; decreases calcium influx | IV | Adult |
| Zinc phosphide poisoning | 1g/hr IV x 24hr, then 1g q6hr x 5-7 days | Cardioprotective | IV | Adult |