How does this medication work? What will it do for me?

Magnesium hydroxide belongs to two groups of medications: laxatives and antacids. It is used to relieve occasional constipation and also to relieve symptoms caused by heartburn, upset stomach, or indigestion.

For constipation, magnesium hydroxide works by increasing the water content and volume of stool, which helps produce a bowel movement. For heartburn, it works by neutralizing stomach acid.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor or pharmacist has not recommended it.

What form(s) does this medication come in?

This medication is available as a 385 mg chewable tablet.

How should I use this medication?

For constipation, the recommended daily dose is 6 to 8 chewable tablets, or 30 mL to 60 mL of oral suspension.

  • For children aged 6 to 11 years old, the usual dose is 3 to 6 chewable tablets, or 15 mL to 30 mL of oral suspension per day.
  • For children 2 to 5 years of age, the usual dose is 1 to 3 chewable tablets, or 5 mL to 15 mL of oral suspension per day.
  • The dose of magnesium hydroxide for children under 2 years of age is based on weight. Talk to your doctor before giving this medication to children under 2 years of age.

For heartburn, the recommended dose for adults is 2 to 4 chewable tablets, or 5 mL to 15 mL of oral suspension up to 4 times a day. For children, the daily dose is the same as that for constipation, however the dose may be divided and given up to 4 times daily (e.g., a 6-year old may take 2 chewable tablets 3 times a day for a total of 6 tablets daily).

Shake the suspension well before taking it. Use an oral syringe or measuring spoon to measure each dose of the liquid, as it gives a more accurate measurement than household teaspoons.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor or pharmacist has recommended a dose different from the ones above, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as recommended by your doctor or pharmacist.

Store this medication at room temperature and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take magnesium hydroxide if you:

  • are allergic to magnesium hydroxide or any ingredients of the medication
  • have abdominal pain, nausea, or vomiting
  • have heart block
  • have seriously reduced kidney function

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • nausea
  • diarrhea
  • vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • signs of kidney problems (e.g., thirst, flushing, dizziness, muscle weakness, confusion)

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • symptoms of a severe allergic reaction (e.g., hives; difficulty breathing; swelling of the mouth, tongue, face, or throat)
Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Digestive tract symptoms: Fever, nausea, vomiting, abdominal pain, or bloating could be symptoms of appendicitis. Speak with your doctor before taking magnesium hydroxide if you have any of these symptoms.

If you have an ileostomy or colostomy, it is recommended that you avoid magnesium hydroxide and other laxatives.

Heart disease: Magnesium can cause a condition called heart block, a slowing down of the heart rate. Due to this side effect, magnesium hydroxide is generally not recommended for people with heart block.

Kidney function: If you have decreased function or kidney disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Long-term use: This medication should not be taken daily for more than one week. Long-term use can make your bowels dependent on this medication to function. If you experience constipation for more than one week, contact your doctor.

Myasthenia gravis: Myasthenia gravis is a condition that causes specific muscle weakness. Magnesium hydroxide may cause the symptoms of myasthenia gravis to get worse. If you have myasthenia gravis, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Rectal bleeding or lack of bowel movement: If you experience rectal bleeding or do not have a bowel movement after using this medication, contact your doctor. These symptoms may mean you have a more serious condition.

Sudden change in bowel habits: If you've noticed a sudden, persistent change in your bowel habits over the last 2 weeks, talk to your doctor before taking this medication.

Pregnancy: Occasional use of magnesium hydroxide is considered safe during pregnancy. If you have concerns, talk your doctor about whether you should continue to take magnesium hydroxide.

Breast feeding: Occasional use of magnesium hydroxide is considered safe while breast feeding. If you are a breast-feeding mother and have concerns, talk to your doctor about whether you should continue breast feeding.

What other drugs could interact with this medication?

There may be an interaction between magnesium hydroxide and any of the following:

  • angiotensin converting enzyme inhibitors (ACEIs; e.g., captopril, ramipril)
  • alfacalcidol
  • allopurinol
  • amphetamines (e.g., dextroamphetamine, lisdexamphetamine)
  • antipsychotic agents (e.g., chlorpromazine, perphenazine)
  • "azole" antifungals (e.g., itraconazole, ketoconazole)
  • bisacodyl
  • bisphosphonates (e.g., alendronate, didronate)
  • bosutinib
  • calcitriol
  • calcium channel blockers (e.g., diltiazem, nifedipine, verapamil)
  • calcium polystyrene sulfonate
  • cefuroxime
  • chloroquine
  • corticosteroids (e.g., dexamethasone, hydrocortisone, prednisone)
  • dabigatran etexilate
  • dasatinib
  • delavirdine
  • dexmethylphenidate
  • erlotinib
  • fexofenadine
  • gabapentin
  • iron salts (e.g., iron sucrose, ferrous gluconate, ferrous sulfate)
  • isoniazid
  • lactulose
  • mesalamine
  • methylphenidate
  • misoprostol
  • multivitamins/minerals (with adek, folate, iron)
  • mycophenolate
  • neuromuscular-blocking agents (e.g., pancuronium, succinylcholine)
  • nilotinib
  • penicillamine
  • phenytoin
  • phosphate supplements
  • ponatinib
  • protease inhibitors (e.g., indinavir, lopinavir, saquinavir)
  • quinidine
  • quinine
  • quinolone antibiotics (e.g., ciprofloxacin, norfloxacin, ofloxacin)
  • sodium polystyrene sulfonate
  • tetracyclines (e.g. doxycycline, minocycline, tetracycline)

Do not take other medications 2 hours before or 2 hours after taking magnesium hydroxide. Magnesium hydroxide may reduce the effectiveness of other medications.

If you are taking other medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.