Pharmacology of drugs acting on the gastrointestinal tract MCQs With Answer is a focused review for B.Pharm students covering mechanisms, therapeutic uses, adverse effects and interactions of agents used in acid-peptic disorders, motility disturbances, antiemetics, laxatives, antidiarrheals and specific antisecretory therapies. This concise set emphasizes key drug classes—antacids, H2-receptor antagonists, proton pump inhibitors, mucosal protectants, prokinetics, antiemetics, opioid receptor modulators, and newer secretagogues—along with clinical scenarios like H. pylori eradication and IBS management. Expect questions testing mechanism of action, pharmacokinetics, safety in pregnancy, CYP interactions and bedside choices to deepen your applied pharmacology understanding. ‘Now let’s test your knowledge with 30 MCQs on this topic.’
Q1. Which drug irreversibly inhibits the gastric H+/K+ ATPase, producing long-lasting suppression of acid secretion?
- Ranitidine
- Omeprazole
- Sucralfate
- Cimetidine
Correct Answer: Omeprazole
Q2. Which H2-receptor antagonist is a potent inhibitor of multiple CYP450 enzymes and is associated with gynecomastia and sexual dysfunction?
- Famotidine
- Nizatidine
- Cimetidine
- Ranitidine
Correct Answer: Cimetidine
Q3. Which mucosal protective agent forms a viscous barrier over ulcers and requires an acidic environment for activation?
- Misoprostol
- Sucralfate
- Bismuth subsalicylate
- Magnesium hydroxide
Correct Answer: Sucralfate
Q4. Which drug is a prostaglandin E1 analogue used for prevention of NSAID-induced gastric ulcers but is contraindicated in pregnancy?
- Misoprostol
- Omeprazole
- Sucralfate
- Ranitidine
Correct Answer: Misoprostol
Q5. Which antacid component can cause hypermagnesemia in renal failure patients?
- Aluminum hydroxide
- Calcium carbonate
- Magnesium hydroxide
- Sodium bicarbonate
Correct Answer: Magnesium hydroxide
Q6. Which antibiotic is commonly part of first-line triple therapy for H. pylori along with a PPI and clarithromycin?
- Tetracycline
- Metronidazole
- Amoxicillin
- Rifampicin
Correct Answer: Amoxicillin
Q7. Which agent used as an antiemetic antagonizes 5-HT3 receptors and is effective for chemotherapy-induced nausea?
- Ondansetron
- Metoclopramide
- Promethazine
- Prochlorperazine
Correct Answer: Ondansetron
Q8. Metoclopramide’s prokinetic action is primarily due to antagonism of which receptor in the GI tract?
- 5-HT3 receptor
- Dopamine D2 receptor
- Muscarinic M3 receptor
- H2 receptor
Correct Answer: Dopamine D2 receptor
Q9. Loperamide treats diarrhea by acting on which receptor type in the gut?
- Peripheral mu-opioid receptor
- Central kappa-opioid receptor
- Muscarinic receptor
- Serotonin receptor
Correct Answer: Peripheral mu-opioid receptor
Q10. Which laxative class increases stool bulk by absorbing water and is considered safest for long-term use?
- Osmotic laxatives (e.g., lactulose)
- Stimulant laxatives (e.g., bisacodyl)
- Bulk-forming laxatives (e.g., psyllium)
- Surfactant laxatives (e.g., docusate)
Correct Answer: Bulk-forming laxatives (e.g., psyllium)
Q11. Which drug is a chloride channel activator used for chronic idiopathic constipation and opioid-induced constipation?
- Lubiprostone
- Linaclotide
- Senna
- Polyethylene glycol
Correct Answer: Lubiprostone
Q12. Linaclotide relieves constipation by agonism of which receptor, increasing intestinal cyclic GMP?
- Guanylate cyclase-C (GC-C)
- Muscarinic M3 receptor
- Serotonin 5-HT4 receptor
- Beta-2 adrenergic receptor
Correct Answer: Guanylate cyclase-C (GC-C)
Q13. Which prokinetic macrolide acts as a motilin receptor agonist useful for diabetic gastroparesis but can cause tachyphylaxis?
- Erythromycin
- Azithromycin
- Clarithromycin
- Roxithromycin
Correct Answer: Erythromycin
Q14. Which antiemetic that blocks NK1 (neurokinin-1) receptors is often combined with 5-HT3 antagonists for chemotherapy-induced nausea?
- Aprepitant
- Promethazine
- Ondansetron
- Metoclopramide
Correct Answer: Aprepitant
Q15. Bismuth subsalicylate aids H. pylori therapy by which of the following actions?
- Systemic acid suppression
- Local mucosal protection and antimicrobial effect
- Direct inhibition of H+/K+ ATPase
- Anticholinergic reduction of motility
Correct Answer: Local mucosal protection and antimicrobial effect
Q16. Which PPI interaction is clinically important because it can reduce activation of clopidogrel (a prodrug)?
- Omeprazole inhibiting CYP2C19
- Omeprazole inducing CYP3A4
- Omeprazole inhibiting CYP2D6
- Omeprazole inducing CYP1A2
Correct Answer: Omeprazole inhibiting CYP2C19
Q17. Which medication is used to treat secretory diarrhea from VIPoma and carcinoid tumors by inhibiting hormone secretion?
- Octreotide
- Loperamide
- Diphenoxylate
- Bismuth subsalicylate
Correct Answer: Octreotide
Q18. Which IBS medication for diarrhea-predominant IBS is a 5-HT3 antagonist reserved due to risk of ischemic colitis?
- Alosetron
- Lubiprostone
- Eluxadoline
- Linaclotide
Correct Answer: Alosetron
Q19. Which antacid component can cause milk-alkali syndrome when taken in excess?
- Magnesium hydroxide
- Aluminum hydroxide
- Calcium carbonate
- Sodium bicarbonate
Correct Answer: Calcium carbonate
Q20. Which drug used for hepatic encephalopathy is a non-absorbable antibiotic that reduces gut ammonia-producing bacteria?
- Rifaximin
- Metronidazole
- Vancomycin
- Neomycin
Correct Answer: Rifaximin
Q21. Which class of antiemetics carries a risk of extrapyramidal side effects and tardive dyskinesia due to central dopamine blockade?
- 5-HT3 antagonists (e.g., ondansetron)
- Atypical antipsychotics
- Dopamine D2 antagonists (e.g., metoclopramide, prochlorperazine)
- Antihistamines (e.g., promethazine)
Correct Answer: Dopamine D2 antagonists (e.g., metoclopramide, prochlorperazine)
Q22. Which antidiarrheal is chemically related to meperidine but combined with atropine to discourage abuse?
- Loperamide
- Diphenoxylate
- Octreotide
- Bismuth subsalicylate
Correct Answer: Diphenoxylate
Q23. Which agent increases lower esophageal sphincter tone and accelerates gastric emptying via 5-HT4 agonism?
- Cisapride (historical)
- Ranitidine
- Sucralfate
- Omeprazole
Correct Answer: Cisapride (historical)
Q24. In peptic ulcer disease, eradication of H. pylori typically requires combination therapy; which of the following is NOT a recommended component of standard triple therapy?
- Proton pump inhibitor
- Amoxicillin
- Clarithromycin
- Metoclopramide
Correct Answer: Metoclopramide
Q25. Which drug commonly used as an antacid may decrease absorption of tetracyclines and fluoroquinolones by chelation?
- Sodium bicarbonate
- Calcium carbonate
- Magnesium-containing antacids
- Aluminum hydroxide
Correct Answer: Magnesium-containing antacids
Q26. Which antisecretory drug class can increase risk of C. difficile infection and community-acquired pneumonia when used long-term?
- H2-receptor antagonists
- Proton pump inhibitors
- Antacids
- Prokinetic agents
Correct Answer: Proton pump inhibitors
Q27. Which drug used for constipation is a chloride channel activator that can cause nausea as a common adverse effect?
- Lubiprostone
- Linaclotide
- Senna
- Polyethylene glycol
Correct Answer: Lubiprostone
Q28. Which drug enhances esophageal and gastric motility by antagonizing peripheral dopamine receptors but can cross the blood–brain barrier causing central side effects?
- Domperidone
- Metoclopramide
- Cisapride
- Erythromycin
Correct Answer: Metoclopramide
Q29. Which antacid is best avoided in patients with renal failure due to aluminum accumulation and consequent osteomalacia risk?
- Magnesium hydroxide
- Aluminum hydroxide
- Calcium carbonate
- Sodium bicarbonate
Correct Answer: Aluminum hydroxide
Q30. Which drug used for IBS with constipation is a mixed mu-opioid receptor agonist and delta-opioid receptor antagonist used for IBS-D instead?
- Eluxadoline
- Loperamide
- Lubiprostone
- Linaclotide
Correct Answer: Eluxadoline
