Proton pump inhibitors, H2 blockers, laxatives, and antiemetics with their mechanisms and side effects tested on USMLE Step 1.
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- What is the mechanism of action of proton pump inhibitors (PPIs)?
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They irreversibly inhibit the H+/K+ ATPase pump in gastric parietal cells.- Name two commonly used proton pump inhibitors.
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Omeprazole and esomeprazole (also pantoprazole and lansoprazole).- When should PPIs be taken relative to meals for best effect?
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About 30 to 60 minutes before a meal.- Long-term PPI use increases the risk of ____ infection because reduced gastric acid fails to kill ingested pathogens.
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Clostridioides difficile- Why does chronic PPI use increase fracture risk?
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Reduced acid impairs calcium absorption, weakening bone over time.- Why can long-term PPI therapy cause vitamin B12 deficiency?
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Gastric acid is needed to release B12 from dietary protein for absorption.- What electrolyte abnormality is associated with long-term PPI use?
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Hypomagnesemia.- What happens to acid secretion if a PPI is stopped abruptly after long-term use?
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Rebound acid hypersecretion occurs.- Besides GI effects, what infection risk is increased by PPI-induced hypochlorhydria?
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Community-acquired pneumonia.- PPIs are first-line therapy for which gastrin-secreting tumor syndrome?
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Zollinger-Ellison syndrome.- What is the mechanism of action of H2 receptor antagonists?
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They reversibly block histamine H2 receptors on gastric parietal cells, reducing acid secretion.- Which H2 blocker is a potent inhibitor of cytochrome P450 enzymes?
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Cimetidine.- What antiandrogenic side effect can cimetidine cause in men?
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Gynecomastia (also impotence).- Name two H2 blockers other than cimetidine.
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Ranitidine and famotidine.- How does the acid-suppressing potency of H2 blockers compare to PPIs?
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H2 blockers are less potent and less effective for severe reflux or ulcer healing.
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