Rabeprazole is used to treat certain conditions in which there is too much acid in the stomach. It is used to treat duodenal ulcers and gastroesophageal reflux disease (GERD), a condition in which the acid in the stomach washes back up into the esophagus. Rabeprazole is also used to treat Zollinger-Ellison disease, a condition in which the stomach produces too much acid.