Magnesium hydroxide has the chemical formula Mg(OH)2. It is available naturally as the mineral brucite. It is a white or colorless, odorless powder and is sparingly soluble in water. It is an alkaline hydroxide compound. It is generally prepared by reacting magnesium sulfate or chloride with sodium hydroxide.
The major use of magnesium hydroxide is as an antacid for stomach upsets. Magnesium hydroxide is alkaline and hence, it can be used to neutralize the acidic pH within the stomach. Thus magnesium hydroxide is a short-term cure for acidity.
Magnesium hydroxide is available in the form of tablets or capsules, which are orally ingested with water. They are mostly slow-release drugs and their effect sets in within 30 minutes to 3 hours of their intake. They are available in the form of combination drugs under brand names such as Maalox, Di-Gel, etc.
A serious problem with magnesium hydroxide is that it interacts with various other body nutrients, such as folic acid, iron and potassium. Magnesium hydroxide inhibits folic acid absorption, which is needed for the synthesis of vitamin B12 in the body. Persons who take digoxin or digitalis, both potassium-depleting diuretics, may suffer chronic problems due to intake of magnesium hydroxide. Magnesium hydroxide is also very effective as a laxative, but it reduces the potassium content within the body, which may cause muscle cramps. Hence it is necessary to replenish the potassium content in the body after consuming a magnesium hydroxide laxative. The diet must also ideally be supplemented with iron and folic acid.
Magnesium hydroxide should not be used very often as a laxative. The body may tend to forget its natural defecation process and become addicted to the use of laxative. A doctor must be immediately consulted if magnesium hydroxide fails to void the bowels even after a long time. The problem may be something other than simple constipation.