What is the recommended dosage and usage of magnesium oxide for treating heartburn, indigestion, and magnesium deficiency?

Magnesium Oxide Dosage and Usage Guidelines

For treating heartburn, indigestion, and magnesium deficiency, magnesium oxide should be administered at a dose of 400 mg (241.2 mg elemental magnesium) 1-2 tablets daily for magnesium supplementation and 1 tablet twice daily as an antacid. 1

Dosage Recommendations by Condition

For Heartburn and Indigestion (Antacid Use)

• Take 1 tablet (400 mg) twice daily or as directed by a physician 1
• Magnesium oxide contains 241.2 mg of elemental magnesium per 400 mg tablet 1
• Administering at night when intestinal transit is slowest can help maximize absorption 2

For Magnesium Deficiency

• Take 1-2 tablets (400-800 mg) daily or as directed by a physician 1
• For mild to moderate deficiency, a total daily dose ranging from 12-24 mmol (approximately 480-960 mg elemental magnesium) is recommended 2, 3
• For long-term magnesium repletion, 300-600 mg of elemental magnesium orally per day is typically sufficient 4

For Constipation

• The American Gastroenterological Association conditionally recommends magnesium oxide for adults with chronic idiopathic constipation who have failed other therapies 2
• Start at a lower dose and increase if necessary based on response 2
• A median treatment dose of 600 mg/day has been shown effective in pediatric constipation studies 5

Administration Considerations

• Divide supplementation into multiple doses throughout the day for continuous repletion 3
• Administering magnesium oxide at night when intestinal transit is slowest can improve absorption 2, 3
• Liquid or dissolvable forms are generally better tolerated than pills 2
• For patients with short bowel syndrome, magnesium oxide is commonly given as gelatin capsules of 4 mmol (160 mg) to a total of 12-24 mmol daily 2

Monitoring and Precautions

• Avoid use in patients with renal insufficiency due to risk of hypermagnesemia 2, 6
• Monitor for common side effects including diarrhea, abdominal distension, and gastrointestinal intolerance 2
• In patients with normal renal function, serum magnesium concentration may increase but typically not to critical levels 5
• For patients with short bowel syndrome, correct dehydration and sodium depletion before magnesium supplementation to avoid secondary hyperaldosteronism 7, 2

Special Considerations

• Higher doses (800 mg daily) have been shown to reduce gastrointestinal complications following cardiac surgery 8
• Approximately 15% of orally administered magnesium oxide is absorbed in the body, with peak plasma concentration occurring 3 hours after administration 6
• If oral supplements don't normalize magnesium levels, oral 1-alpha hydroxy-cholecalciferol (0.25-9.00 μg daily) may improve magnesium balance, but requires monitoring of serum calcium 2
• For severe magnesium deficiency with acute clinical manifestations, parenteral administration of 24-48 mEq magnesium/day for 3-5 days may be required 4

Therapeutic Algorithm for Magnesium Supplementation

1. Assess severity of deficiency or condition requiring treatment 2
2. For mild to moderate deficiency or heartburn/indigestion, start with oral magnesium oxide at recommended doses 1
3. If treating constipation, start at a lower dose and increase gradually based on response 2
4. Monitor for side effects, particularly diarrhea which may limit dosing 2
5. For patients with malabsorption or short bowel syndrome, consider higher doses or alternative administration strategies 2
6. If oral therapy fails, consider parenteral administration for severe deficiency 4