Mint-O-Mag

As an antacid, magnesium hydroxide suspension neutralizes gastric acid by reacting with hydrochloric acid in the stomach to form magnesium chloride and water. It is practically insoluble in water and does not have any effect until it reacts with the hydrochloric acid in the stomach. There, it decreases the direct acid irritant effect and increases the pH in the stomach leading to inactivation of pepsin. Magnesium hydroxide enhances the integrity of the mucosal barrier of the stomach as well as improving the tone of both the gastric and esophageal sphincters. As a laxative, the magnesium hydroxide works by increasing the osmotic effect in the intestinal tract and drawing water in. This creates distension of the colon which results in an increase in peristaltic movement and bowel evacuation.

The suspension of magnesium hydroxide is ingested and enters the stomach. According to the amount ingested, the magnesium hydroxide will either act as an antacid or a laxative. Through the ingestion of 0.5-1.5 grams (in adults) the magnesium hydroxide will act by simple acid neutralization in the stomach. The hydroxide ions from the magnesium hydroxide suspension will combine with the acidic H+ ions of the hydrochloric acid made by the stomachs parietal cells. This neutralization reaction will result in the formation of magnesium chloride and water. Through the ingestion of 2-5 grams (in adults) the magnesium hydroxide acts as a laxative in the colon. The majority of the suspension is not absorbed in the intestinal tract and will create an osmotic effect to draw water into the gut from surrounding tissues. With this increase of water in the intestines, the feces will soften and the intraluminal volume of the feces will increase. These effects still stimulate intestinal motility and induce the urge to defecate. Magnesium hydroxide will also release cholecystokinin (CCK) in the intestines which will accumulate water and electrolytes in the lumen and furthermore increase intestinal motility.

Unless a patient is deficient in magnesium, very little is absorbed by the intestine. Overall, about 15%-50% of the magnesium hydroxide suspension is absorbed systemically. However, it does not undergo any metabolism as it is rapidly excreted in the urine.

About 15%-50% of magnesium hydroxide is absorbed very slowly through the small intestine.

After oral administration, up to 50% of the magnesium hydroxide suspension may be absorbed as magnesium ions through the small intestines and then rapidly excreted in the urine through the kidneys. The unabsorbed drug is mainly excreted in the feces and saliva.

The peak action and distribution of magnesium hydroxide are variable.

Magnesium hydroxide is mainly excreted in the urine by the kidneys. Since the kidneys play a major role in its clearance, individuals with renal failure are at risk of hypermagnesemia with long term consumption as the appropriate amounts of magnesium may not be excreted.