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

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

See Also

• Hypermagnesemia
• Hypomagnesemia
• QT prolongation
• Eclampsia