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Pharmacology · USMLE Step 1

USMLE Pharmacology: GI Drugs

Proton pump inhibitors, H2 blockers, and antiemetics with mechanism of action and one signature side effect per card.

37 cards · basic cards · AI-written, checked twice. Edit anything.

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What is the mechanism of action of proton pump inhibitors (PPIs)?
They irreversibly inhibit H+/K+-ATPase in gastric parietal cells.
What is a signature long-term adverse effect of PPI use on bone health?
Increased risk of fractures (osteoporosis-related).
Name a commonly used proton pump inhibitor drug.
Omeprazole (or esomeprazole, lansoprazole, pantoprazole).
PPI use increases the risk of which enteric infection due to reduced gastric acidity?
Clostridioides difficile infection.
Long-term PPI use can cause deficiency of which vitamin?
Vitamin B12.
Long-term PPI use can cause which electrolyte abnormality?
Hypomagnesemia.
What happens to gastric acid secretion if a PPI is abruptly stopped after chronic use?
Rebound acid hypersecretion.
Omeprazole can reduce the efficacy of which antiplatelet drug via CYP2C19 inhibition?
Clopidogrel.
When should PPIs be taken relative to meals for best effect?
Before meals, about 30 to 60 minutes prior.
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 causes antiandrogenic effects such as gynecomastia and impotence?
Cimetidine.
Why does cimetidine cause many drug interactions?
It potently inhibits cytochrome P450 enzymes.
Which H2 blocker is preferred for having the fewest CYP450 drug interactions and CNS effects?
Famotidine.
Why can cimetidine cause confusion in elderly or renally impaired patients?
It crosses the blood-brain barrier and can accumulate with reduced renal clearance.
What pharmacologic phenomenon limits the long-term effectiveness of H2 blockers?
Tachyphylaxis, meaning tolerance develops with chronic use.

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