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Name: Magnesium Hydroxide

Pregnancy Category C

Drug classes

  • Antacid
  • Laxative

Mechanisms of action

  • Antacid (magnesium hydroxide, magnesium oxide): neutralizes or reduces gastric acidity, resulting in an increase in the pH of the stomach and duodenal bulb and inhibition of the  proteolytic activity of pepsin.
  • Laxative (magnesium citrate, magnesium hydroxide): attracts/retains water in intestinal lumen and distends bowel; causes the duodenal secretion of cholecystokinin, which stimulates fluid secretion and intestinal motility.


  • Symptomatic relief of upset stomach associated with hyperacidity
  • Hyperacidity associated with peptic ulcer, gastritis, peptic esophagitis, gastric hyperacidity, and hiatal hernia
  • Prophylaxis of GI bleeding, stress ulcers, aspiration pneumonia
  • Short-term relief of constipation; evacuation of the colon for rectal and bowel examination


  • Contraindicated in the presence of allergy to magnesium products.
  • Use caution in the presence of renal insufficiency.

Adverse effects

  • CNS: Dizziness, fainting, sweating
  • GI: Diarrhea, nausea, perianal irritation
  • Metabolic: Hypermagnesemia and toxicity in renal failure patients

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