Antacid





An antacid is a substance which neutralizes stomach acidity and is used to relieve heartburn, indigestion or an upset stomach.

Medical uses
Antacids are available over the counter and are taken by mouth to quickly relieve occasional heartburn, the major symptom of gastroesophageal reflux disease and indigestion. Treatment with antacids alone is symptomatic and only justified for minor symptoms.

Antacids are distinct from acid-reducing drugs like H2-receptor antagonists or proton pump inhibitors and they do not kill the bacteria Helicobacter pylori, which causes most ulcers.

Non-particulate antacids (sodium citrate, magnesium trisilicate) increase gastric pH with little or no effect on gastric volume. Sodium citrate should be given within 1 hour of surgery to be the most effective.

Side effects
Versions with magnesium may cause diarrhea, and brands with calcium or aluminium may cause constipation and rarely, long-term use may cause kidney stones. Long-term use of versions with aluminium may increase the risk for getting osteoporosis.

Mechanism of action
When excessive amounts of acids are produced in the stomach the natural mucous barrier that protects the lining of the stomach can damage the esophagus in people with acid reflux. Antacids contain alkaline ions that chemically neutralize stomach gastric acid, reducing damage and relieving pain.

Formulations and brands
Antacids may be formulated with other active ingredients such as simethicone to control gas or alginic acid to act as a physical barrier to acid.

Effervescents
Effervescent tablets are tablets which are designed to dissolve in water, and then release a level of carbon dioxide. The common ingredients are citric acid and sodium bicarbonate, which react when in contact with water to produce carbon dioxide. Effervescent antacids may also contain aspirin, sodium carbonate, or tartaric acid.

Well known brands are Alka-Seltzer, Eno and Andrews.

Algeldrate
Under the generic name algeldrate, aluminium hydroxide is used as an antacid. Aluminium hydroxide is preferred over other alternatives such as sodium bicarbonate because Al(OH)3, being insoluble, does not increase the pH of stomach above 7 and hence, does not trigger secretion of excess stomach acid. Brand names include Alu-Cap, Aludrox, Gaviscon, and Pepsamar. In 2016 Gaviscon was one of the biggest selling branded over-the-counter medications sold in Great Britain, with sales of £62 million. It reacts with excess acid in the stomach, reducing the acidity of the stomach content, which may relieve the symptoms of ulcers, heartburn or dyspepsia. Such products can cause constipation, because the aluminum ions inhibit the contractions of smooth muscle cells in the gastrointestinal tract, slowing peristalsis and lengthening the time needed for stool to pass through the colon. Some such products are formulated to minimize such effects through the inclusion of equal concentrations of magnesium hydroxide or magnesium carbonate, which have counterbalancing laxative effects.