From the FDA Drug Label
DIRECTIONS Antacid Directions:■ take 1 tablet twice a day or as directed by a physician Magnesium Supplement Directions: ■take 1 to 2 tablets daily or as directed by a physician The maximum dose of magnesium oxide is 2 tablets daily as per the label instructions, which corresponds to 800mg of magnesium oxide (2 x 400mg) or 482.4mg of elemental magnesium (2 x 241.2mg) 1.
- The maximum dose is not explicitly stated in terms of elemental magnesium or magnesium oxide in milligrams, but can be calculated based on the tablet dosage.
- It is essential to follow the physician's directions, as the dose may vary depending on individual needs 1.
From the Research
The maximum daily dose of magnesium oxide for adults should not exceed 1200 mg per day, considering it contains about 60% elemental magnesium, as higher doses may lead to adverse effects such as diarrhea, abdominal cramping, and nausea, especially in patients with renal impairment 2. When using magnesium oxide for constipation, a single dose of 400-800 mg of elemental magnesium can be taken, but should not exceed 800 mg daily. For heartburn or indigestion, 400-800 mg daily in divided doses is common. It's essential to note that people with kidney disease should use caution and consult a healthcare provider before taking magnesium supplements, as impaired kidney function can lead to magnesium accumulation in the body. Magnesium works by drawing water into the intestines to soften stool for constipation relief, and by neutralizing stomach acid for heartburn relief. A recent study published in the Journal of neurogastroenterology and motility in 2019 found that magnesium oxide was effective in improving defecation status and shortening colonic transit time in patients with chronic constipation, with a dose of 0.5 g × 3/day for 28 days 3. However, the most recent and highest quality study, published in Nutrients in 2021, emphasizes the importance of considering the most appropriate dose, serum concentration, drug-drug interactions, and potential side effects when using magnesium oxide, especially in the elderly and patients with renal impairment 2. Key points to consider when prescribing magnesium oxide include:
- The dose should be individualized based on the patient's condition and response to treatment
- Patients with renal impairment should be closely monitored for signs of magnesium accumulation
- Magnesium oxide can interact with other medications, such as antibiotics and blood thinners, and these interactions should be carefully considered when prescribing the medication.