http://search-herb.com/item.php?group_id=49&id=175&n=prevacid Prevacid decreases the amount of acid produced in the stomach. Prevacid is used to treat and prevent stomach and intestinal ulcers, erosive esophagitis (damage to the esophagus from stomach acid), and other conditions involving excessive stomach acid such as Zollinger-Ellison syndrome. Prevacid may also be used for purposes other than those listed in this medication guide.