Famotidine is used for:

Treating and preventing ulcers; treating and preventing heartburn associated with acid indigestion and sour stomach. It is also used to treat gastroesophageal reflux disease (GERD), conditions that cause increased acid secretion, and esophagitis. It also may be used for other conditions as determined by your doctor.

Famotidine is an H₂ (histamine) blocker. It reduces stomach acid by blocking one of the chemicals (histamine) that stimulates the release of acid into the stomach...