Omeprazole, a drug sold under the brand name is Prilosec, is a medication used to suppress the production of acid in the stomach. Omeprazole is classified as a proton pump inhibitor and is indicated for the treatment of frequent heartburn due to gastroesophageal disease and for the treatment of gastric and duodenal ulcers. My mother has had IBS for years and has used prilosec for quite a while. A few months ago, she was put on Omeprazole and after 2 weeks of bad upper stomach pain, she stopped taking it. 20 mg PO once daily for 4 to 8 weeks. If a patient does not respond to 8 weeks of treatment, an additional 4 weeks of treatment may be given. If there is recurrence of erosive esophagitis, additional 4 to 8 week courses of omeprazole may be considered. Find patient medical information for Prilosec Oral on WebMD including its uses, side effects and safety, interactions, pictures, warnings and user ratings. @alisha-- Yea, everyone reacts to medications differently. Omeprazole can cause digestion related side effects. This might be diarrhea for some people, constipation for others and just nausea for some others. Pancreatitis. Long-term use of omeprazole may cause pancreatitis, according to Drugs.com. Pancreatitis is the inflammation of the pancreas, an organ that produces digestive enzymes important for the digestion of fats and carbohydrates. Consumer information about the OTC and prescription drug omeprazole (Prilosec, Zegerid Prilosec OTC, Zegerid OTC) used for treating acid-induced inflammation and ulcers of the stomach and duodenum, gastroesophageal reflux disease (GERD), heartburn, and Zollinger-Ellison Syndrome. Omeprazole can be used in the treatment of gastroesophageal reflux disease (GERD), peptic ulcers, erosive esophagitis, Zollinger-Ellison syndrome, and eosinophilic esophagitis. Although omeprazole is a helpful medication to treat acid, there are other natural alternatives that can provide us with the same benefits without the side effects Find patient medical information for Omeprazole Oral on WebMD including its uses, side effects and safety, interactions, pictures, warnings and user ratings.