Antacids containing calcium

Calcium-containing antacids are over-the-counter medications that typically use calcium carbonate or calcium phosphate as their active ingredients to neutralize stomach acid. They are formulated as chewable tablets, capsules, or liquids and are widely used for rapid relief of symptoms such as heartburn, acid indigestion, sour stomach, and mild, occasional gastroesophageal reflux. By neutralizing gastric hydrochloric acid, they raise intragastric pH, inactivate the proteolytic enzyme pepsin, and reduce irritation of the esophageal and gastric mucosa. The primary mechanism of action involves direct chemical reaction between calcium salts (often calcium carbonate) and gastric acid to form water and soluble calcium salts while consuming free hydrogen ions, thereby decreasing acidity. In addition to neutralizing acid, the calcium ions can increase lower esophageal sphincter tone and stimulate esophageal peristalsis, which promotes clearance of refluxed acid back into the stomach and contributes to symptom relief. In the small intestine, much of the calcium is re-precipitated as insoluble salts and excreted in the stool, limiting systemic absorption at typical antacid doses. Clinically, calcium-containing antacids are used for short-term, intermittent symptom control rather than for long-term management of underlying disease. Because they provide rapid onset of action, they are often taken as needed after meals or at bedtime, and sometimes in anticipation of triggers such as spicy foods. At higher doses or with prolonged use, they also contribute to overall calcium intake and may affect calcium and phosphate balance, especially in individuals with low or high dietary calcium or with chronic kidney disease.