Nexium decreases the amount of acid produced in the stomach. It is used to treat symptoms of gastroesophageal reflux disease (GERD) and other conditions involving excessive stomach acid such as Zollinger-Ellison syndrome. It is also used to promote healing of erosive esophagitis (damage to your esophagus caused by stomach acid). It may also be given to prevent gastric ulcer caused by infection with helicobacter pylori (H. pylori) or by the use of nonsteroidal anti-inflammatory drugs (NSAIDs).