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. 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 is a medicine called a proton pump inhibitor (PPI). It reduces the amount of acid in your stomach. It's used to treat or prevent conditions and symptoms such as: Omeprazole usually comes as tablets, capsules and liquid that you swallow. Some tablets can be dissolved in water. Prilosec (omeprazole) is used to treat symptoms of GERD and other conditions caused by excess stomach acid. Includes Prilosec side effects, interactions and indications. 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). What is omeprazole used for? Omeprazole is used to treat heartburn and certain other conditions caused by too much acid in the stomach. Gastroesophageal reflux disease (GERD), where stomach. What is Omeprazole used for? Over-the-counter omeprazole treats frequent heartburn, defined as heartburn that occurs two or more times a week. Omeprazole is used to treat conditions that appear in the patient having too much stomach acid. This medication is available over-the-counter and in stronger doses via prescription. 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] Omeprazole is a proton pump inhibitor that is used to treat symptoms of gastroesophageal reflux disease and other conditions caused by excess stomach acid.