Magnesium Hydroxide

Please note: these are basic guidelines, refer to your doctor for a professional medical opinion.

Popular brand names:

Milk of Magnesia

Popular combinations:

Gelusil-S, Maalox, Maalox plus, Mucaine

Drug group:

Antacid and laxative

Prescription needed?

No

What does it do?

Magnesium hydroxide can be used alone as a laxative, or it can be used in combination with aluminium hydroxide (which causes constipation) as an antacid:

• It relieves indigestion and heartburn
• It prevents pain caused by stomach and duodenal ulcers, gastritis, and reflux oesophagitis

How does it work?

• Magnesium hydroxide rapidly neutralizes stomach acid, making it a fast-acting antacid
• It also draws salt and water from the bowel walls, making it useful to soften the faeces

How should it be used?

• Magnesium hydroxide should be taken with water, an hour after food, and at bedtime
• Allow 1–2 hours between magnesium hydroxide and other medications
• It is for occasional use only, and should not be taken for prolonged periods

What is the typical dosage?

Your doctor will recommend a dosage tailored to your need, but typically:

• Antacid: 1–4 x daily as needed, 1–2g per dose (tablets); 5–10ml per dose (liquid)
• Laxative: Once daily, at bedtime, 30-45ml per dose (liquid)

How quickly will it start to work?

Antacid: within 15 minutes

Laxative: 2–8 hours      
                          

How long will the effects last?

2–4 hours                

When should I stop using it?

Can be safely stopped as soon as no longer needed     

Is it safe for prolonged use?

Long-term indigestion/heartburn in 40+ year olds needs investigation.

If you have kidney dysfunction, prolonged use may result in magnesium accumulation, which can cause drowsiness, dizziness, and weakness.                                                                  

What are the possible side effects?

The following have been reported:

• More common: diarrhoea
• Less common: dizziness, muscle weakness
• Report to your doctor before taking your next dose if you experience: severe side effects

What other considerations are important?

Dosage may be adjusted by your doctor under certain conditions.

• Certain health problems: kidney problems, bowel disorders
• Other medicines: interferes with the absorption of many drugs including tetracycline antibiotics, iron supplements, phenytoin, gabapentin, penicillamine, enteric-coated tablets
• Pregnancy and breast-feeding: No evidence of risk, but other treatment may be more appropriate, discuss with your doctor
• Children: Not recommended in children <3 years, reduced dose necessary for older children
• Over 60: No special problems
• Driving and hazardous work: No known problems
• Alcohol: Avoid, alcohol irritates the stomach and may reduce the benefits of the drug