Milk of Magnesia

Mechanism of Action

Laxative: Promotes osmotic retention of fluid, which distends the colon with increased peristaltic activity and stimulates bowel evacuation

Antacid: Reacts with hydrochloric acid in stomach to form magnesium chloride

Absorption

Bioavailability: 15-30%

Onset: 0.5-6 hr (laxative)

Elimination

Excretion: Urine (up to 30% as absorbed magnesium), feces (as unabsorbed drug)

For adults and children age 12 and older using Milk of Magnesia as a laxative, the recommended liquid dose is two to four tablespoons once a day, preferably at bedtime.

The dose should be followed by 8 ounces (a full glass) of water.

For younger children ages 6 to 11 years, the dose is usually one or two tablespoons.

The doses of tablets vary by age and are listed on the product label.

If you are planning to give Milk of Magnesia to a child under age 6 years, check in with the child's doctor first.

For indigestion, the usual liquid dose of Milk of Magnesia is one to three teaspoons up to four times a day for adults and children 12 years and older. For younger children, check with their doctor before giving it to them.

Milk of Magnesia Overdose

Do not take more than the maximum recommended dose of Milk of Magnesia, as noted on the label, in a 24-hour period.

If you suspect an overdose, call your doctor right away.

Missed Dose of Milk of Magnesia

Usually, Milk of Magnesia is taken as needed to help constipation or other problems.

If your doctor has recommended you take it regularly and you miss a dose, take it as soon as you remember.

However, if it's almost time for your next dose, skip that missed dose and get back on your regular schedule. Never double up on doses.

Do not use magnesium hydroxide without a doctor's advice if you have stomach pain, nausea, or vomiting.

Ask a doctor or pharmacist if it is safe for you to take this medicine if you have other medical conditions, especially kidney disease.

It is not known whether magnesium hydroxide will harm an unborn baby. Ask a doctor before using this medicine if you are pregnant.

It is not known whether magnesium hydroxide passes into breast milk or if it could harm a nursing baby. Ask a doctor before using this medicine if you are breast-feeding a baby.

Since magnesium hydroxide is used when needed, you may not be on a dosing schedule. If you are on a schedule, use the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not use extra medicine to make up the missed dose.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include severe diarrhea, muscle weakness, mood changes, slow or irregular heartbeats, and little or no urinating.

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

Other drugs may interact with magnesium hydroxide, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

• Bad taste in your mouth. This most often goes back to normal.
• Loose stools (diarrhea).

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-FDA-1088. You may also report side effects at http://www.fda.gov/medwatch.

Applies to magnesium hydroxide: compounding powder, oral concentrate, oral suspension, oral tablet chewable

Gastrointestinal

Diarrhea may occur and is occasionally severe enough to cause dehydration and electrolyte abnormalities.[Ref]

Gastrointestinal side effects have included diarrhea and minor gastrointestinal discomfort.[Ref]

General

General side effects have included signs and symptoms of hypermagnesemia. These have included hypotension, nausea, vomiting, EKG changes, respiratory depression, mental depression and coma.[Ref]

Magnesium may be systemically absorbed following administration of magnesium hydroxide. In patients with normal renal function, increased magnesium elimination in the urine occurs and no significant changes in serum magnesium levels would be expected. However, magnesium may accumulate in patients with renal insufficiency.[Ref]

Some side effects of Milk of Magnesia may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.