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Magnesium Sulfate

Trade Names: Epsom Salt, Sulfamag

Class: Electrolyte, anticonvulsant

Pharmacology:

Onset – IV – Immediate IM – 3-4 hr
Duration – IV – 30 min IM – 3-4 hr

Reduces striated muscle contractions and blocks peripheral neuromuscular transmission by reducing acetylcholine release at myoneural junction. Used in the management of seizures associated with with toxemia of pregnancy. Other uses include uterine relaxation, as a bronchodilator after beta-agonist and anticholinergic agents have been used, and replacement therapy for magnesium deficiency.

Indications:
  • Seizures of eclampsia
  • Cardiac Arrest only if torsades de pointes is suspected or hypomagnesemia
  • Life threatening ventricular dysrhythmias attributable to digitalis toxicity
  • Suspected hypomagnesemia
  • Status asthmaticus not responsive to beta-adrenergic drugs

Contraindications:

Heart block or myocardial damage

Cautions:

  • CNS depressant effects may be enhanced if the patient is taking other CNS depressants
  • Serious changes in cardiac function may occur with cardiac glycosides

Packaging:

10%, 12.5%, 50% solution in 40, 80, 100, and 125 mg/mL

Doses:

Seizure activity associated with pregnancy: 1-4 g IV; max dose 30-40 g/day

Pulseless arrest (for hypomagnesemia or torsades de pointes), Status asthmaticus:

  • Adult: 1-2 g (2-4 mL of a 50% solution) diluted in 10 mL of D5W IV/IO push
  • Pediatric: 25-50 mg/kg IV/IO max 2g over 10-20 min

Torsades de Pointes with pulse or AMI with hypomagnesemia

  • Adult: Loading dose of 1-2 g in 50-100 mL of D5W over 5-60 min IV; follow with 0.5-1 g/hr IV
  • Pediatric: Same as pulseless
 Side Effects:
  • Diaphoresis
  • Facial flushing
  • Hypotension
  • Depressed reflexes
  • Hypothermia
  • Reduced HR
  • Circulatory collapse
  • Respiratory depression
  • Diarrhea
  • Nausea and vomiting

Special Considerations

Pregnancy safety – Category A
Not to be administered in the 2 hr before delivery
Convulsions may occur up to 48 hrs after delivery
The cure for toxemia is delivery of the baby
Must be used w/ caution in patients with renal failure


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