Magnesium oxide: Uses, Dosage, Side Effects and More

This information is not country-specific. Please refer to the Singapore prescribing information.

Generic Medicine Info

Indications and Dosage

Oral
Dietary supplement

Adult: 400-800 mg daily. Max: 800 mg/24 hours. Doses are preferably taken with meals. Dosage and treatment recommendations may vary among individual products and between countries (refer to specific product guidelines).

Oral
Antacid

Adult: 400 mg bid. Max: 800 mg/24 hours. Doses are preferably taken with meals. Dosage and treatment recommendations may vary among individual products and between countries (refer to specific product guidelines).

Special Precautions

Renal impairment. Elderly. Pregnancy and lactation.

Adverse Reactions

Gastrointestinal disorders: Diarrhoea, gastrointestinal disturbances.
Metabolism and nutrition disorders: Hypermagnesaemia.

Patient Counseling Information

When used as an antacid: Do not use for >2 weeks or exceed the recommended daily dose unless recommended by the doctor.

Drug Interactions

May decrease the absorption of isoniazid, digoxin, oral tetracyclines, and oral iron preparations.

Action

Description:
Mechanism of Action: Magnesium oxide is an antacid that neutralises acid by reacting with hydrochloric acid in the stomach. As a dietary supplement, magnesium is an important cofactor in many enzymatic reactions in the body that are involved in the synthesis of protein and metabolism of carbohydrates.
Pharmacokinetics:
Distribution: Crosses the placenta and enters breast milk (as magnesium).
Excretion: Via urine; faeces (as unabsorbed drug).

Storage

Store between 15-30°C.

MIMS Class

Antacids, Antireflux Agents & Antiulcerants

ATC Classification

A02AA02 - magnesium oxide ; Belongs to the class of magnesium-containing antacids.

References

Antacids. UpToDate Lexidrug, AHFS DI (Adult and Pediatric) Online. American Society of Health-System Pharmacists, Inc. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 08/09/2025.

Brayfield A, Cadart C (eds). Magnesium Oxide. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 08/09/2025.

Magnesium Oxide (Mg Supplement) Tablet (Nationwide Pharmaceutical LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 08/09/2025.

Magnesium Oxide 400 mg Tablet (Spirit Pharmaceuticals LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 08/09/2025.

Magnesium Oxide. UpToDate Lexidrug, Lexi-Drugs Multinational Online. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 08/09/2025.

Magoral (42 Siammedicare). MIMS Thailand. http://www.mims.com/thailand. Accessed 16/09/2025.

Disclaimer: This information is independently developed by MIMS based on Magnesium oxide from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2025 MIMS. All rights reserved. Powered by MIMS.com