Magnesium is a naturally occurring mineral. Magnesium is important for many systems in the body especially the muscles and nerves.

Mag-Ox 400 is used as a supplement to maintain adequate magnesium in the body.

Mag-Ox 400 is also used as an antacid to treat indigestion, or as a laxative to relieve occasional constipation.

Mag-Ox 400 may also be used for purposes not listed in this medication guide.

Before you take Mag-Ox 400, tell your doctor about all your medical conditions or allergies, and all the medicines you are using. Also make sure your doctor knows if you are pregnant or breast-feeding. In some cases, you may not be able to take this medicine, or you may need a dose adjustment or special precautions.

Use exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Take this medicine with a full glass of water.

When using this medicine as a laxative, it may be best to take your dose at bedtime.

Mag-Ox 400 may be taken with food if it upsets your stomach.

Call your doctor if your symptoms do not improve after 7 days of treatment, or if symptoms get worse.

Store at room temperature away from moisture and heat.

You should not use Mag-Ox 400 if you are allergic to it.

Ask a doctor or pharmacist if it is safe for you to use Mag-Ox 400 if you have other medical conditions, especially:

• kidney disease;

• heart disease;

• nausea, vomiting;

• a blockage in your intestines;

• low levels of calcium in your blood; or

• a sudden change in bowel habits for 2 weeks or longer.

It is not known whether Mag-Ox 400 will harm an unborn baby. Ask a doctor before using this medicine if you are pregnant.

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

Do not give this medicine to a child without medical advice.

Mag-Ox 400 should not be given to a child younger than 6 years old.

Since Mag-Ox 400 is sometimes used when needed, you may not be on a dosing schedule. If you are on a schedule, take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take 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 nausea, vomiting, weakness, breathing problems, slow reflexes, weak pulse, extreme drowsiness, and feeling dizzy or light-headed.

Mag-Ox 400 can make it harder for your body to absorb other medicines you take by mouth. Avoid taking other medicines within 2 hours before or 2 hours after you take this medicine. You may need to wait 4 hours to take your other medicines after taking this medicine. Ask your doctor how to best schedule your medications.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Mag-Ox 400 may cause serious side effects. Stop using Mag-Ox 400 and call your doctor at once if you have:

• rectal bleeding;

• coughing up blood or vomit that looks like coffee grounds;

• bloody or tarry stools; or

• no bowel movement after using Mag-Ox 400 as a laxative.

Common side effects of Mag-Ox 400 may include:

• diarrhea; or

• upset stomach.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Ask a doctor or pharmacist if it is safe for you to take Mag-Ox 400 if you are also using any of the following drugs:

• an antibiotic;

• a diuretic or "water pill";

• penicillamine;

• a blood thinner--warfarin, Coumadin, Jantoven; or

• medicine to treat osteoporosis or Paget's disease--alendronate, ibandronate, risedronate, Fosamax, Boniva, Actonel, and others.

This list is not complete. Other drugs may interact with magnesium oxide, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.