Omeprazole is a proton pump inhibitor used in the treatment of dyspepsia, peptic ulcer disease (PUD), gastroesophageal reflux disease (GORD/GERD) and Zollinger-Ellison syndrome . Omeprazole suppresses gastric acid secretion by specific inhibition of the H + /K + ATPase enzyme system at the secretory surface of the gastric parietal cell .