Which drug class reduces acid release by blocking histamine receptors in the stomach?

• A. H2-receptor blockers
• B. Proton Pump Inhibitors
• C. Antacids
• D. Antiemetic

Answer: (A)

Histamine stimulates stomach acid production by binding to H2 receptors on parietal cells, which increases cAMP and activates the proton pumps that secrete acid. H2-receptor blockers are competitive antagonists that bind to those same H2 receptors, blocking histamine from triggering the acid-secreting cascade. As a result, less acid is produced, especially for nocturnal and meal-stimulated secretion. This mechanism distinguishes them from other drug classes that reduce acid through different pathways, such as proton pump inhibitors that directly inhibit the proton pump, or antacids that neutralize already-secreted acid.