VTNE Practice Question of the Day: Pharmacology & Pharmacy - Vet Tech Board Exam Prep

Topic: Pharmacology & Pharmacy

Famotidine is an H2 receptor antagonist used to reduce gastric acid secretion. How does its mechanism differ from proton pump inhibitors like omeprazole?

A. Famotidine irreversibly inhibits the H+/K+-ATPase pump like omeprazole, but also blocks H2 receptors, providing dual-pathway acid suppression for longer duration

B. Famotidine activates prostaglandin-mediated mucosal defense while omeprazole provides only antacid buffering, making famotidine superior for treating erosive gastritis in dogs

C. Famotidine competitively and reversibly blocks H2 receptors on parietal cells, reducing histamine-stimulated acid secretion, while omeprazole irreversibly blocks the proton pump

D. Famotidine only blocks gastrin-mediated secretion at enterochromaffin-like cells, whereas omeprazole blocks histamine-mediated secretion at the H2 receptor on parietal cells

E. Both famotidine and omeprazole competitively block the H+/K+-ATPase pump but famotidine has shorter duration due to lower affinity for the enzyme complex

Think you know it? Comment your answer (A-E) and your reasoning before scrolling.

Correct Answer: >!C. Famotidine competitively and reversibly blocks H2 receptors on parietal cells, reducing histamine-stimulated acid secretion, while omeprazole irreversibly blocks the proton pump!<

Explanation: >!CORRECT (C — Famotidine: Reversible H2 Blockade; Omeprazole: Irreversible Pump Inhibition): Famotidine competitively blocks histamine H2 receptors on gastric parietal cells, reducing histamine-stimulated cAMP production and acid secretion. Its action is reversible and competitive. Omeprazole (PPI) irreversibly inhibits the H+/K+-ATPase proton pump after covalent activation. PPIs are more potent and longer-acting (24-36h) than H2 blockers (8-12h) and are preferred for severe ulcers.

A — Famotidine irreversibly inhibits pump: Incorrect — famotidine does not affect the proton pump; it is a reversible H2 receptor antagonist only. B — Famotidine activates prostaglandins: Incorrect — prostaglandin enhancement describes misoprostol; neither famotidine nor omeprazole primarily work via prostaglandins. C — Correct — see above. D — Famotidine targets ECL cells: Incorrect — famotidine blocks H2 receptors on parietal cells, not ECL cells; gastrin acts on ECL cells (not famotidine's target). E — Both block the pump: Incorrect — only omeprazole (and other PPIs) blocks the H+/K+-ATPase; famotidine is strictly an H2 receptor antagonist.

MEMORY ANCHOR: 'Famotidine = H2 BLOCKER = reversible, competitive. Omeprazole = PPI = IRREVERSIBLE pump blocker. PPI wins for potency. H2 blocker for mild/maintenance.'

References: Plumb DC. Plumb's Veterinary Drug Handbook, 9th ed. Wiley-Blackwell, 2018; Boothe DM. Small Animal Clinical Pharmacology and Therapeutics, 2nd ed. Elsevier, 2012.!<

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