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Phillips' Milk of Magnesia Side Effects

Generic Name: magnesium hydroxide

Note: This document contains side effect information about magnesium hydroxide. Some of the dosage forms listed on this page may not apply to the brand name Phillips' Milk of Magnesia.

For the Consumer

Applies to magnesium hydroxide: oral suspension, oral tablet chewable

What are some side effects that I need to call my doctor about right away?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Very upset stomach or throwing up.
  • Very loose stools (diarrhea).
  • Not hungry.
  • Muscle weakness.

What are some other side effects of this drug?

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

For Healthcare Professionals

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


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 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]


1. Emmett M "A comparison of clinically useful phosphorus binders for patients with chronic kidney failure." Kidney Int 66 Suppl 90 (2004): S25-32

2. Johansson G, Backman U, Danielson BG, Fellstrom B, Ljunghall S, Wikstrom B "Biochemical and clinical effects of the prophylactic treatment of renal calcium stones with magnesium hydroxide." J Urol 124 (1980): 770-4

3. Bardhan KD, Hunter JO, Miller JP, Thomson AB, Graham DY, Russell RI, Sontag S, Hines C, Martin T, Gaussen L, et al "Antacid maintenance therapy in the prevention of duodenal ulcer relapse." Gut 29 (1988): 1748-54

4. Johansson G, Backman U, Danielson BG, Fellstrom B, Ljunghall S, Wikstrom B "Magnesium metabolism in renal stone formers. Effects of therapy with magnesium hydroxide." Scand J Urol Nephrol Suppl 53 (1980): 125-34

5. Fung MC, Weintraub M, Bowen DL "Hypermagnesemia: elderly over-the-counter drug users at risk." Arch Fam Med 4 (1995): 718-23

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.