The present invention is related to novel oral compositions comprising an irreversible gastric H.sup.+/K.sup.+-ATPase proton pump inhibitor (PPI) as a gastric acid secretion inhibitor and one or more small carboxylic acid molecules as parietal cell activators in the gastric lumen. Unexpectedly, the compositions of the present invention are capable of enhancing the anti-acid activity of PPI in the stomach. The present invention further relates to a method of using such compositions to reduce gastric acid secretion in a mammal.