An antacid is a substance which neutralizes stomach acidity and is used to relieve heartburn, indigestion or an upset stomach.
Antacids are available over the counter and are taken by mouth to quickly relieve occasional heartburn, the major symptom of gastroesophageal reflux disease and also 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.