GI GI Pharmacology and Medications 1 — Questions and Answers
Question 1: Proton pump inhibitors (PPIs) work by irreversibly inhibiting which enzyme in gastric parietal cells?
- Carbonic anhydrase
- H+/K+-ATPase (proton pump) (Correct answer)
- Histamine H2 receptor
- Gastrin receptor
Correct answer: H+/K+-ATPase (proton pump)
PPIs covalently and irreversibly bind the H+/K+-ATPase enzyme, blocking the final step of acid secretion in parietal cells.
Question 2: Mesalamine (5-ASA) is the first-line therapy for mild to moderate disease in which condition?
- Crohn's disease of the small bowel
- Ulcerative colitis (Correct answer)
- Microscopic colitis
- Pouchitis after IPAA
Correct answer: Ulcerative colitis
Mesalamine is the cornerstone of induction and maintenance therapy for mild-to-moderate ulcerative colitis due to its topical anti-inflammatory effect on the colonic mucosa.
Question 3: Which antibiotic regimen is currently recommended for first-line H. pylori eradication in the United States (clarithromycin-resistant regions)?
- Amoxicillin + clarithromycin for 7 days
- Bismuth quadruple therapy (PPI + bismuth + tetracycline + metronidazole) for 10–14 days (Correct answer)
- Metronidazole monotherapy for 14 days
- Ciprofloxacin + metronidazole for 10 days
Correct answer: Bismuth quadruple therapy (PPI + bismuth + tetracycline + metronidazole) for 10–14 days
Due to rising clarithromycin resistance, bismuth quadruple therapy for 10–14 days is recommended as first-line H. pylori treatment in most US regions.
Question 4: Infliximab and adalimumab are anti-TNF agents used in IBD; which is administered as an intravenous infusion rather than subcutaneous injection?
- Adalimumab
- Certolizumab pegol
- Infliximab (Correct answer)
- Golimumab
Correct answer: Infliximab
Infliximab is a chimeric monoclonal antibody administered by IV infusion, whereas adalimumab and other anti-TNF agents are given subcutaneously.
Question 5: Lactulose is used in the management of hepatic encephalopathy through which primary mechanism?
- Reducing intestinal transit time to decrease ammonia absorption
- Increasing renal excretion of ammonia
- Acidifying the colon to trap ammonium and reduce bacterial ammonia production (Correct answer)
- Directly chelating ammonia in the portal circulation
Correct answer: Acidifying the colon to trap ammonium and reduce bacterial ammonia production
Lactulose is metabolized by colonic bacteria to lactic and acetic acids, lowering pH and converting NH3 to NH4+, which is poorly absorbed and excreted in stool.
Question 6: Ondansetron belongs to which drug class and acts by blocking which receptor to control nausea and vomiting?
- Antihistamine; H1 receptor
- 5-HT3 antagonist; serotonin receptor (Correct answer)
- Dopamine antagonist; D2 receptor
- NK1 antagonist; substance P receptor
Correct answer: 5-HT3 antagonist; serotonin receptor
Ondansetron is a selective 5-HT3 serotonin receptor antagonist that blocks vagal afferent signals triggering the vomiting center.
GI GI Pharmacology and Medications 1
Proton pump inhibitors (PPIs) work by irreversibly inhibiting which enzyme in gastric parietal cells?