Learn about the side effects of omeprazole, from common to rare, for consumers and healthcare professionals. Nonprescription (over-the-counter) omeprazole is used to treat frequent heartburn (heartburn that occurs at least 2 or more days a week) in adults. Omeprazole is in a class of medications called proton-pump inhibitors. It works by decreasing the amount of acid made in the stomach. Learn about omeprazole (Prilosec) usage and dosing. Read the latest news and reviews about the drug as well as potential side effects and popular alternatives. Omeprazole is a medication that treats conditions that cause too much stomach acid like heartburn, stomach ulcers and reflux disease. It works by reducing the amount of acid in your stomach. Omeprazole, sold under the brand names Prilosec and Losec among others, is a medication used in the treatment of gastroesophageal reflux disease (GERD), peptic ulcer disease, and Zollinger–Ellison syndrome. [1] Find patient medical information for Omeprazole (Prilosec, Prilosec OTC) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user ratings NHS information about the medicine omeprazole, including what it's used for, who can take it, how to take it and side effects. Omeprazole (Prilosec) is a common proton pump inhibitor (PPI). It’s a generic medication available with a prescription. Certain doses are also available over the counter (OTC). Omeprazole is a popular choice for treating symptoms and conditions related to too much stomach acid. Omeprazole is used to treat certain conditions where there is too much acid in the stomach. It is used to treat gastric and duodenal ulcers, erosive esophagitis, and gastroesophageal reflux disease (GERD). Omeprazole is a proton pump inhibitor that is used to treat symptoms of gastroesophageal reflux disease and other conditions caused by excess stomach acid.