Omeprazole belongs to a class of drugs known as proton pump inhibitors (PPIs). Omeprazole is used to treat certain stomach and esophagus problems (such as acid reflux and ulcers). It works by decreasing the amount of acid the stomach makes. It relieves symptoms such as heartburn, difficulty swallowing, and persistent cough. This medication helps heal acid damage to the stomach and esophagus, helps prevent ulcers, and may help prevent cancer of the esophagus.