Lansoprazole belongs to a group of drugs called proton pump inhibitors. It decreases the amount of acid produced in the stomach.
Lansoprazole 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. Over-the-counter lansoprazole (Prevacid OTC) is used to treat frequent heartburn that happens 2 or more days per week.