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