Magnesium Hydroxide

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mag-NE-ze-um hi-DROKS-ide - Pronunciation guide

Brand Names

  • Milk of Magnesia


Magnesium hydroxide is a compound of magnesium, which is a naturally occurring mineral, combined with hydroxide. As a suspension in water, it is known as Milk of Magnesia. Magnesium hydroxide is a common component of antacids and laxatives.


Magnesium hydroxide is used as an antacid to neutralize stomach acid and also as a laxative. In some cases, it is prescribed to help relieve mild colic.

Magnesium hydroxide will reduce stomach acidity for a short period of time, but needs to be given every two hours to be effective. For this reason, some veterinarians prefer using amitidine, ranitidine, or omeprazole because of their longer-acting effectiveness and better time compliance on the part of the person administering the drug.

Dosage and Administration

Magnesium Hydroxide
Method Dosage
(click row for calculator)
Concentration Period Duration
Oral 200-250 ml   3 times daily NA


  • Extra-label use of drugs in treating animals is allowable only by licensed veterinarians within the context of a valid veterinarian-client-patient relationship, and does not include drug use in treating animals by the layman (except under the supervision of a licensed veterinarian).

Side Effects

None noted if used according to directions.


Diarrhea caused by magnesium hydroxide carries away much of the body's supply of potassium. With prolonged use, extra potassium should be given to prevent cramping of muscles.


Allow at least two hours between other drugs and administration of magnesium hydroxide.


More pronounced diarrhea occurs with overdose.


Milk of MagnesiaMilk of Magnesia


About the Author

EquiMed Staff

EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.