Famotidine injection is used in people who are hospitalized to treat certain conditions in which the stomach produces too much acid or to treat ulcers (sores in the lining of the stomach or intestine) that were not successfully treated with other medications. Famotidine injection is also used on a short-term basis in people who cannot take oral medication to treat ulcers, to prevent ulcers from returning after they have healed, to treat gastroesophageal reflux disease (GERD, a condition in which backward flow of acid from the stomach causes heartburn and injury of the esophagus [tube between the throat and the stomach]), and to treat conditions where the stomach produces too much acid, such as Zollinger-Ellison syndrome (tumors in the pancreas and small intestine that caused increased production of stomach acid). Famotidine injection is in a class of medications called H2 blockers. It works by decreasing the amount of acid made in the stomach.