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Pharmacology · single question

Omeprazole prevents acid secretion by which mechanism of action?

  1. Prostaglandin analog protecting gastric mucosa
  2. Antacid neutralizing gastric acid
  3. Proton pump inhibitor (H+/K+ ATPase blocker)
  4. H2 receptor antagonist
Show answer and explanation

Correct answer: C. Proton pump inhibitor (H+/K+ ATPase blocker)

  • A. Misoprostol is a prostaglandin analog used for mucosal protection; this is not the mechanism of omeprazole.
  • B. Antacids (e.g., calcium carbonate) chemically neutralize existing stomach acid; they do not block secretion.
  • C. Correct. Omeprazole is a proton pump inhibitor (PPI) that irreversibly blocks the H+/K+ ATPase (proton pump) on gastric parietal cells, preventing the final step of acid secretion regardless of stimulus.
  • D. H2 receptor antagonists (e.g., ranitidine, famotidine/Pepcid) block histamine H2 receptors on parietal cells — this is NOT the mechanism of omeprazole.

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