Magnesium Oxide

 Action Neutralizes gastric acid, thereby increases pH of stomach and duodenal bulb; also increases lower esophageal sphincter tone.

 Indications Symptomatic relief of upset stomach associated with hyperacidity, including heartburn, gastroesophageal reflux, acid indigestion and sour stomach; relief of hyperacidity associated with peptic ulcer, gastritis, peptic esophagitis, gastric hyperacidity and hiatal hernia. Also used for treatment of hypomagnesemia, or magnesium depletion resulting from malnutrition, restricted diet, alcoholism or magnesium-depleting drugs.

 Contraindications Standard considerations.

 Route/Dosage

ADULTS: PO 140 mg (caps) 3–4 times/day or 400–840 mg/day (tabs).

 Interactions

Iron: Decreased pharmacological effect of iron. Nitrofurantoin: Decreased pharmacological effect of nitrofurantoin. Penicillamine: Decreased pharmacological effect of penicillamine. Tetracyclines: Decreased pharmacological effect of tetracyclines.

 Lab Test Interferences None well documented.

 Adverse Reactions

GI: Laxative effect (diarrhea); rebound hyperacidity. META: Hypermagnesemia. OTHER: Milk-alkali syndrome.

 Precautions

Pregnancy: Category B. Lactation: Undetermined. Renal insufficiency: Caution with renal impairment to avoid hypermagnesemia and toxicity.

 Administration/Storage

• Administer caps or tabs with full glass of water or other liquid.
• Give 1–2 hr before or after other medications if possible.
• Store in airtight container in cool location unless otherwise specified by manufacturer.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies. Note renal disease.
• Monitor for symptoms of renal insufficiency (elevated BUN and creatinine, decreased urine output).
• Encourage patient to increase fluid intake.
• Monitor serum magnesium levels in patients being treated for hypomagnesemia and in patients with impaired renal function.
• Assess for heartburn and indigestion. Note location, duration, character and precipitating factors.

 Patient/Family Education

• Advise patient that drug may be laxative and cause diarrhea.
• If being used for antacid effect, instruct patient to notify physician if symptoms are not relieved or if black, tarry stools or “coffee-ground” omitus occurs. These symptoms can indicate bleeding.
• Explain that drug should not be used routinely for laxative effect. Advise patient to use other forms of bowel regulation such as increasing fluid intake, mobility and bulk in diet.
• Warn patient not to take other medications within 2 hr of antacids.