What mechanism is primarily affected by H2 blockers such as ranitidine and cimetidine?

H2 blockers, such as ranitidine and cimetidine, primarily work by inhibiting the action of histamine at the H2 receptors located in the gastric parietal cells. These H2 receptors play a crucial role in the process of gastric acid secretion. When histamine binds to these receptors, it stimulates the secretion of stomach acid; therefore, blocking these receptors reduces acid production, which is beneficial in treating conditions like gastroesophageal reflux disease (GERD) and peptic ulcers.

By targeting the histamine receptors specifically, H2 blockers effectively decrease the overall acidity of the stomach, leading to symptom relief from acid-related disorders. Other mechanisms, such as prostaglandin production, psychoactive pathways, and cholecystokinin receptors, are not directly influenced by H2 blockers and do not play a central role in their function. This distinction highlights the specific action of H2 blockers in the management of gastrointestinal acidity.