Esomeprazole reduce the production of acid in the stomach, Nexium reduces the amount of acid backing up into the esophagus and causing reflux symptoms. Your body adjusts to the new medicine. Nexium decreases the amount of acid produced in the stomach. For the majority of gastric ulcers. Nexium is a type of medicine known as an acid pump inhibitor which works by decreasing the acid produced by acid pumps. Your body adjusts to the new medicine. The enzyme in the wall of the stomach that produces acid. Nexium is a type of medicine known as an acid pump inhibitor which works by decreasing the acid produced by acid pumps.