Mag-Ox, Maox, Par-Mag, Uro-Mag
Classifications: antacid; saline cathartic;
Therapeutic: antacid
; magnesium supplement; laxative
Prototype: Magnesium hydroxide
Pregnancy Category: A


400 mg, 420 mg, 500 mg tablets; 140 mg capsules


Nonsystemic antacid with high neutralizing capacity and relatively long duration of action.

Therapeutic Effect

Acts as an antacid in low doses and a mild saline laxative at higher doses. Also effective as a magnesium supplement.


Essentially the same as magnesium hydroxide. May also be used as magnesium supplement.


Abdominal pain, nausea, vomiting, diarrhea, severe kidney dysfunction, fecal impaction, intestinal obstruction or perforation, ileus; rectal bleeding, colostomy, ileostomy; AV block; hypermagnesia; children <2 y.

Cautious Use

Cardiac disease, renal disease, renal impairment; electrolyte imbalance; pregnancy (category A), lactation.

Route & Dosage

Adult: PO 280–1500 mg with water or milk q.i.d., p.c. and h.s.

Adult: PO 2–4 g with water or milk h.s.

Magnesium Supplement
Adult: PO 400–1200 mg/d in divided doses


  • Separate administration of this drug from other oral drugs by 1–2 h.
  • Store at 15°–30° C (59°–86° F) in airtight containers. On exposure to air, magnesium oxide rapidly absorbs moisture and carbon dioxide.

Adverse Effects (≥1%)

GI: Diarrhea, abdominal cramps, nausea; hypermagnesemia, kidney stones (chronic use).


Drug: See magnesium hydroxide.


Absorption: 30–50% from GI tract. Elimination: In urine.

Nursing Implications

Assessment & Drug Effects

  • Monitor for dehydration, hypokalemia, and hyponatremia (see Appendix F) since drug may cause intense bowel evacuation.
  • Lab tests: Check patients on prolonged therapy periodically for electrolyte imbalance (i.e., hypermagnesemia).

Patient & Family Education

  • Liquid preparation is reportedly more effective than the tablet form, as with other antacids.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

© 2006-2023 Last Updated On: 01/29/2023 (0)
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