What is the mechanism of action of proton pump inhibitors?

Proton pump inhibitors (PPIs) work by binding irreversibly to the hydrogen/potassium ATPase enzyme system (the proton pump) located in the gastric parietal cells. This action effectively inhibits the final step of gastric acid production, leading to a significant reduction in stomach acid secretion. By targeting the proton pump specifically, PPIs provide a more profound and sustained decrease in acid secretion compared to other classes of medications, such as H2 receptor antagonists.

In contrast to the other mechanisms mentioned, PPIs do not neutralize gastric acid directly, nor do they block H2 receptors or enhance gastric mucosal defense. H2 receptor antagonists, for instance, reduce acid secretion by blocking the action of histamine on H2 receptors, which is different from the effect of PPIs. Furthermore, while enhancing mucosal defense can be beneficial for certain conditions, PPIs primarily focus on reducing acid output to treat conditions like gastroesophageal reflux disease (GERD) and peptic ulcer disease.