GERD and Peptic Ulcer Disease USMLE Step 1 Practice Question
A 45-year-old man presents with a 3-month history of retrosternal burning pain that awakens him at night and worsens 30–60 minutes after eating spicy foods or large meals. He denies dysphagia, weight loss, or melena. Vital signs are normal. Upper endoscopy shows erythematous mucosa in the distal esophagus without ulceration or Barrett's changes. A diagnosis of erosive GERD is made, and omeprazole 20 mg daily is initiated. The patient experiences symptom resolution within 2 weeks. Which of the following best explains the mechanism by which omeprazole provides therapeutic benefit in this patient?
Answer choices
- ACompetitive antagonism of histamine-2 receptors on gastric parietal cells, reducing basal and stimulated acid secretion
- BIrreversible inhibition of the H+/K+-ATPase pump on the apical membrane of parietal cells, suppressing acid secretion for 24–48 hoursCorrect answer
- CCoating of the gastric mucosa with a protective bicarbonate layer that neutralizes residual acid and promotes mucosal healing
- DNonselective inhibition of gastric proton pump isoforms including H+/K+-ATPase and V-ATPase, affecting multiple cellular compartments
- ENeutralization of free hydrogen ions in the gastric lumen through direct chemical reaction, increasing intragastric pH to >4
- FCompetitive inhibition of gastrin receptors on parietal cells, preventing acetylcholine-mediated acid secretion
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