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Name: Magnesium sulfate

Pregnancy Category A

Drug classes

  • Electrolyte
  • Anticonvulsant
  • Laxative

Therapeutic actions

Cofactor of many enzyme systems involved in neurochemical transmission and muscular excitability; prevents or controls convulsions by blocking neuromuscular transmission; attracts/retains water in the intestinal lumen and distends the bowel to promote mass movement and relieve constipation.


  • Hypomagnesemia, replacement therapy (IV)
  • Toxemia/eclampsia/nephritis (IV, IM)
  • Short-term treatment of constipation (PO)
  • Evacuation of the colon for rectal and bowel examinations (PO)
  • Unlabeled use: inhibition of premature labor (parenteral)


Contraindicated in the presence of allergy to magnesium products; heart block, myocardial damage; abdominal pain, nausea, vomiting or other symptoms of appendicitis; acute surgical abdomen, fecal impaction, intestinal and biliary tract obstruction, hepatitis. Do not give during 2
h preceding delivery because of risk of magnesium toxicity in the neonate.

Use caution in the presence of renal insufficiency.

Adverse effects

  • CNS: Weakness, dizziness, fainting, sweating (PO)
  • GI: Excessive bowel activity, perianal irritation (PO)
  • CV: Palpitations (PO)
  • Metabolic: Magnesium intoxication (flushing, sweating, hypotension, depressed relfexes, flaccid paralysis,hypothermia, circulatory collapse, cardiac and CNS depression-parenteral); hypocalcemia with tetany (secondary to treatment of eclampsia-parenteral)

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