Esomeprazole is an inhibitor of the gastric H+/K+-ATPase and the (S) enantiomer of omeprazole (Item No. 14880).{61476} It reversibly inhibits the activity of the H+/K+-ATPase in an enzyme assay. Esomeprazole (30 mg/kg, s.c.) inhibits histamine-induced gastric acid secretion in rats. Formulations containing esomeprazole in complex with magnesium have been used as proton pump inhibitors (PPIs) in the treatment of gastroesophageal reflux disease (GERD), H. pylori eradication, and hypersecretory conditions, as well as in the prevention of non-steroidal anti-inflammatory drug-related gastric ulcer.