Pharmacology
The H2 antagonists are competitive antagonists of histamine at the parietal cell H2 receptor. They suppress the normal secretion of acid by parietal cells and the meal-stimulated secretion of acid. They accomplish this by two mechanisms: Histamine released by ECL cells in the stomach is blocked from binding on parietal cell H2 receptors, which stimulate acid secretion; therefore, other substances that promote acid secretion (such as gastrin and acetylcholine) have a reduced effect on parietal cells when the H2 receptors are blocked.
Like the H1-antihistamines, the H2 antagonists are inverse agonists rather than true receptor antagonists.
Read more about this topic: H2 Antagonist