Lanzol Lansoprazole capsules What do lansoprazole capsules do?LANSOPRAZOLE (Prevacid(R)) prevents the production of acid in the stomach, reducing symptoms and preventing injury to the esophagus, stomach, or intestines. Lansoprazole heals active gastric or duodenal ulcers, and is useful in conditions that cause excessive stomach acid production such as Zollinger-Ellison syndrome.