Magnesium Hydroxide
Magnesium Hydroxide is a dual-action antacid and laxative that neutralizes stomach acid to provide quick relief from heartburn and acid indigestion, while also helping with occasional constipation.
Magnesium Hydroxide is an over-the-counter antacid and laxative used to treat heartburn, acid indigestion, and constipation by neutralizing stomach acid and promoting intestinal water absorption.
Key facts at a glance
- ATC
- A02AA04
- RxNorm
- 6585
- Generic
- Magnesium Hydroxide
- Class
- atc-a02
- Brands
- Milantex, Pedia-Lax Chewable, Inon Ace Tablet, Inon Ace Solution, Maalox Plus, Duo Fusion, Almacone, Mintox Plus, Phillips Milk of Magnesia, Gelusil, Mirafast, Pepcid Complete, Maalox Max, Rolaids Reformulated Aug 2006, Comfort Gel
- Availability
- otc
- Pregnancy
- B
- Lactation
- safe
- Half-life (h)
- 0
- Onset (min)
- 15
- Duration (h)
- 4
- Routes
- oral
- Forms
- oral suspension, chewable tablet, tablet, oral solution, gel
- Regions
- United States, Canada, United Kingdom, European Union, Australia, Japan, India, China, Brazil, Mexico
- Monitoring
- renal function, serum magnesium, electrolyte balance
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 500mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 250mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 400mg daily
- Maximum
- consult physician
- Frequency
- once daily
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
8 groupspregnancy
first trimesteruse lowest effective dose, avoid prolonged use
avoid routine use during pregnancy unless benefits clearly outweigh risks
monitor maternal symptoms and duration of use
Use with caution and monitor for adverse effects.
pregnancy
third trimesteruse lowest effective dose, limit chronic use
avoid chronic high-dose use in third trimester due to potential for neonatal hypermagnesemia
monitor for signs of magnesium accumulation in mother
Use with caution and monitor for adverse effects.
lactation
breastfeedingno dosage adjustment required
compatible with breastfeeding, magnesium hydroxide is minimally excreted in breast milk
no specific monitoring required
pediatric_age
children under 12weight-based dosing required, use pediatric formulations
use only pediatric-specific formulations, do not use adult formulations in children under 12 without medical supervision
monitor for diarrhea and electrolyte balance
Use with caution and monitor for adverse effects.
geriatric
elderlystart with lowest effective dose, consider renal function
use with caution in elderly due to increased risk of magnesium accumulation and electrolyte disturbances
monitor renal function and serum magnesium levels with prolonged use
Use with caution and monitor for adverse effects.
renal_impairment
mild to moderatereduce dose, avoid chronic use
use with caution in renal impairment, monitor serum magnesium levels
regular monitoring of serum magnesium and renal function
Use with caution and monitor for adverse effects.
renal_impairment
severeavoid use or use only under close medical supervision
generally contraindicated in severe renal impairment due to risk of toxicity
frequent serum magnesium monitoring required if used
Use of this medication in this population requires careful consideration of risks and benefits.
hepatic_impairment
anyno adjustment typically required
generally considered safe in hepatic impairment as magnesium hydroxide is not metabolized by liver
standard monitoring only
Statistics and clinical data
Commonly prescribed since
General prescribing information
Drug class
Drug class information
Common uses
Common therapeutic uses
Mechanism of action
Pharmacological mechanism
Treatment of heartburn, acid indigestion, sour stomach, and occasional constipation. Commonly found in over-the-counter antacid products and milk of magnesia formulations.
As an antacid, it neutralizes stomach acid through a chemical reaction. As a laxative, it draws water into the intestines and stimulates bowel movements.
May cause diarrhea in some users. Should not be used for more than 1-2 weeks for constipation without medical advice. Patients with kidney disease should consult a doctor before use. May interact with certain medications; take separately by 1-2 hours.
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 26, 2026. · Read our editorial policy