Magnesium carbonate

Magnesium carbonate is an inorganic compound and the magnesium salt of carbonic acid. It is used in medicine both as an osmotic laxative and as a so-called antacid. In nature, it is most often found in the form of magnesite.

Pharmacodynamics

The action as a laxative can be explained by the osmotic activity of magnesium carbonate. When taken orally, the substance enters the intestine and draws water from the surrounding tissues into the intestine. This increases the volume of the intestinal contents and activates certain nerves located in the intestinal wall. This ultimately triggers bowel movements.

The effect as an antacid is due to the basic properties of the carbonate anion in the compound. After ingestion, the salt enters the stomach where it dissolves into its components, Mg²⁺ and CO₃^2-. These bind the Cl^- and H⁺ ions of the hydrochloric acid and thus neutralize the stomach acid. This raises the pH of the stomach contents within a few minutes. This leads to relief of acid-related complaints such as heartburn.

Pharmacokinetics

Approximately 40-60% of magnesium is absorbed after oral administration. Percent absorption decreases with increasing dose. 30% of the magnesium absorbed is present bound to plasma proteins. Magnesium is excreted unchanged by the kidney. The half-life is approximately 27 hours. The maximum magnesium clearance is directly proportional to the creatinine clearance.

Side effects

In overdose, magnesium impairs neuromuscular transmission, causing weakness and hypoflexia.