Magnesium sulfate

See critical care quick reference for drug doses by weight.

General

• Type: Antiarrhythmics
• Dosage Forms: IV
• Common Trade Names:
• Severe Hypokalemia should warrant checking of Magnesium level and correction if required..

Adult Dosing

• Loading dose = 1-2gm in 10mL D5W over 1-2min (cardiac arrest)
• Loading dose = 1-4gm in 50-100 D5W over 20-60min (spontaneous circulation)

• Eclampsia:
  • Initial: 4 g magnesium sulfate 50% solution (400mg elemental magnesium) to a 10% or 20% solution and give IV over 3 to 4 minutes OR 5mg IM in each buttock
  • Maintenance: 1 to 2 g/hr IV until paroxysms cease

Indications

• Torsades
• Refractory v-tach/fib (regardless of Mg level)
• Eclampsia
• Hypomagnesemia
• Barium poisoning

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

Contraindications

• Allergy to class/drug

Adverse Reactions

Serious

• Hypotension (rare)
• Heart block
• CNS 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

See Also

• Hypermagnesemia
• Hypomagnesemia