Messi Biology states that magnesium hydroxide is a versatile pharmaceutical ingredient commonly used in tablet formulations, possessing good antacid and laxative properties, and is widely used in clinical and healthcare fields. Depending on its different uses in tablets, its functions can be mainly divided into the following aspects:

1. Antacid Effect
Magnesium hydroxide is a weakly alkaline substance that, upon entering the stomach, can neutralize gastric acid (hydrochloric acid), rapidly relieving discomfort symptoms such as heartburn, acid reflux, and stomach pain caused by excessive gastric acid.
Compared to strong alkaline antacids such as sodium bicarbonate, magnesium hydroxide has a milder neutralizing effect, making it less likely to cause “rebound acid secretion.”
It is often used in combination with aluminum hydroxide in compound formulations, where the two combine to synergistically provide antacid effects while counteracting each other’s constipation and diarrhea side effects.
Reaction Example:
Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O
2. Laxative Effect
At high doses, magnesium hydroxide has a laxative effect because it is not easily absorbed in the intestine, and can form a hyperosmotic environment, attracting water into the intestinal lumen, softening the stool, and promoting bowel movements.
It belongs to the saline laxative category, with an onset time usually of 6-12 hours, and is suitable for the adjunctive treatment of constipation patients.
When used in combination with dietary fiber and plant extracts, it can form a gentle bowel-promoting tablet formula.
3. Magnesium Supplement
Magnesium hydroxide is an important source of magnesium and is used as a magnesium supplement in some nutritional supplement tablets.
Appropriate supplementation is beneficial for symptoms such as muscle cramps, anxiety, and insomnia caused by magnesium deficiency.
Compared to other organic magnesium (such as magnesium glycinate and magnesium lactate), its tablet form has lower cost and better stability.
4. Synergistic Regulatory Effect
In compound formulations, magnesium hydroxide can work synergistically with gastric mucosa protectants, prokinetic drugs, etc., to exert comprehensive therapeutic effects.
For example, it can be used in combination with H₂-receptor antagonists/proton pump inhibitors such as ranitidine and omeprazole for the adjunctive treatment of diseases such as gastric ulcers and gastroesophageal reflux.
It can also affect drug release behavior by regulating intestinal pH and has certain application value in controlled-release tablets.