1,4-Dihydro-1-(5-methoxy-1H-benzimidazol-2-yl)-3,5-dimethyl-4-oxo-2-pyridinecarboxylic Acid Ammonium Salt is an impurity of Omeprazole. Omeprazole is a proton pump inhibitor used in the treatment of dyspepsia. It binds to the proton pump hydrogen-potassium adenosine triphosphatase (H+/K+ ATPase) and inhibits its activity and the parietal cell secretion of H+ ions into the gastric lumen.