CAS NO:73590-58-6 Omeprazole belongs to a group of drugs called proton pump inhibitors. It decreases the amount of acid produced in the stomach. Omeprazole is used to treat symptoms of gastroesophageal reflux disease (GERD) and other conditions caused by excess stomach acid. It is also used to promote healing of erosive esophagitis (damage to your esophagus caused by stomach acid). It may also be given together with antibiotics to treat gastric ulcer caused by infection with helicobacter pylori (H. pylori). Omeprazole is available in 10 mg, 20 mg, 40 mg