21.5 : 消化性潰瘍疾患の酸抑制薬：制酸剤

In the gastric lumen, increased acid secretion can form or exacerbate ulcers in the mucosal layer.

Carbonate antacids, like sodium bicarbonate and calcium carbonate, can neutralize this acid, forming salt and water. This raises gastric pH from 1 to 5 and reduces intragastric acidity.

However, the reaction of these antacids with gastric acid also generates CO₂, which, upon accumulation, causes stomach distention and belching.

Additionally, excessive doses of these antacids lead to absorption of unreacted alkali, raising blood's alkalinity and causing metabolic alkalosis.

Moreover, sodium load increases fluid retention in hypertensive patients, while calcium triggers rebound acid secretion.

To mitigate the side effects, magaldrate, a hydroxymagnesium aluminate complex is used.

In gastric acid, it converts into poorly absorbed magnesium and aluminum hydroxides, imparting a sustained antacid effect.

The efficiency of antacids depends on dissolution rate, water solubility, reaction speed with acid, and gastric emptying rate.

Their clearance is faster on an empty stomach, but when taken with food, their duration of action is prolonged.