Introduction: This quiz collection on GIT pharmacology—prokinetics and antiemetics—is designed specifically for M.Pharm students preparing for Advanced Pharmacology-II exams. It covers detailed mechanisms, receptor pharmacology, clinical indications, adverse effects, and important drug interactions relevant to prokinetic and antiemetic agents. The 20 multiple-choice questions probe deeper understanding beyond definitions, addressing pharmacodynamic nuances (5-HT, D2, motilin, NK1, cannabinoid receptors), safety considerations (QT prolongation, tardive dyskinesia, hyperprolactinemia), and evidence-based clinical use in conditions like chemotherapy-induced nausea, gastroparesis, and motion sickness. Each question includes clear options and definitive answers to help strengthen critical thinking and exam readiness.
Q1. Which best describes metoclopramide’s primary prokinetic mechanism?
- D2 receptor antagonist and 5-HT4 agonist
- Muscarinic M3 receptor agonist and motilin receptor antagonist
- Selective 5-HT3 receptor antagonist
- Opioid µ-receptor antagonist
Correct Answer: D2 receptor antagonist and 5-HT4 agonist
Q2. What is the clinical advantage of domperidone compared with metoclopramide?
- Stronger central D2 blockade causing more antiemetic potency
- Does not readily cross the blood–brain barrier, producing fewer extrapyramidal effects
- Acts primarily as a 5-HT3 antagonist reducing QT risk
- Is a potent CYP3A4 inducer and reduces steroid exposure
Correct Answer: Does not readily cross the blood–brain barrier, producing fewer extrapyramidal effects
Q3. Erythromycin acts as a prokinetic by which mechanism?
- Motilin receptor agonist stimulating migrating motor complexes
- Direct cholinesterase inhibition increasing acetylcholine at neuromuscular junctions
- Selective 5-HT3 receptor antagonism in the chemoreceptor trigger zone
- β2-adrenergic receptor agonism relaxing the stomach
Correct Answer: Motilin receptor agonist stimulating migrating motor complexes
Q4. Which major safety concern led to cisapride’s market withdrawal in many countries?
- Severe anticholinergic delirium
- Life-threatening QT interval prolongation and torsades de pointes due to hERG channel blockade
- Irreversible liver failure through mitochondrial toxicity
- Profound hyperprolactinemia with sexual dysfunction
Correct Answer: Life-threatening QT interval prolongation and torsades de pointes due to hERG channel blockade
Q5. For which clinical scenario are 5-HT3 receptor antagonists (e.g., ondansetron) most effective?
- Acute phase of chemotherapy-induced nausea and vomiting (CINV)
- Chronic functional constipation management
- Treatment of gastroparesis to increase antral contractions long-term
- Motion sickness prophylaxis via vestibular blockade
Correct Answer: Acute phase of chemotherapy-induced nausea and vomiting (CINV)
Q6. Which drug is a Neurokinin-1 (NK1) receptor antagonist used to prevent chemotherapy-induced nausea?
- Aprepitant
- Granisetron
- Metoclopramide
- Promethazine
Correct Answer: Aprepitant
Q7. A recognized cardiac adverse effect of ondansetron is:
- Dose-dependent QT interval prolongation
- Marked hypotension via α1 blockade
- Irreversible bradycardia due to vagal stimulation
- Ventricular hypertrophy with chronic use
Correct Answer: Dose-dependent QT interval prolongation
Q8. The pathophysiology of tardive dyskinesia with long-term metoclopramide therapy is best explained by:
- Dopamine D2 receptor blockade leading to receptor upregulation and supersensitivity
- Permanent destruction of nigrostriatal neurons
- Excessive serotonin receptor activation causing neurotoxicity
- Accumulation of cholinergic interneurons in the striatum
Correct Answer: Dopamine D2 receptor blockade leading to receptor upregulation and supersensitivity
Q9. Prucalopride is best characterized pharmacologically as:
- A selective 5-HT4 receptor agonist with minimal cardiac hERG effects used for chronic constipation
- A nonselective muscarinic agonist used primarily for small-bowel ileus
- An H2 receptor antagonist that accelerates gastric emptying
- A peripheral opioid receptor agonist used for diarrhea
Correct Answer: A selective 5-HT4 receptor agonist with minimal cardiac hERG effects used for chronic constipation
Q10. Which antiemetic combines H1 antihistaminic and anticholinergic activity and is commonly used for motion sickness?
- Promethazine (antihistamine with anticholinergic activity)
- Ondansetron (5-HT3 antagonist)
- Aprepitant (NK1 antagonist)
- Metoclopramide (D2 antagonist/5-HT4 agonist)
Correct Answer: Promethazine (antihistamine with anticholinergic activity)
Q11. For prevention of delayed (≥24 hours) chemotherapy-induced nausea and vomiting, the most important drug class to include is:
- NK1 receptor antagonists (e.g., aprepitant) often combined with dexamethasone
- Short-acting benzodiazepines as monotherapy
- Prokinetics such as erythromycin alone
- Topical anticholinergics on the abdomen
Correct Answer: NK1 receptor antagonists (e.g., aprepitant) often combined with dexamethasone
Q12. Scopolamine prevents motion sickness primarily by blocking which receptors in the vestibular nuclei?
- Muscarinic acetylcholine (M1) receptors
- Dopamine D2 receptors
- 5-HT3 receptors
- Opioid µ receptors
Correct Answer: Muscarinic acetylcholine (M1) receptors
Q13. Which of the following is NOT an antiemetic agent?
- Loperamide
- Prochlorperazine
- Ondansetron
- Metoclopramide
Correct Answer: Loperamide
Q14. Dronabinol exerts its antiemetic and appetite-stimulating effects primarily via:
- Agonism at central cannabinoid CB1 receptors
- Blockade of peripheral 5-HT3 receptors
- Stimulation of motilin receptors in the gut
- Inhibition of dopamine reuptake in the chemoreceptor trigger zone
Correct Answer: Agonism at central cannabinoid CB1 receptors
Q15. Which prokinetic agent is commonly employed to increase lower esophageal sphincter tone and accelerate gastric emptying in GERD with gastroparesis?
- Metoclopramide
- Ondansetron
- Fosaprepitant
- Scopolamine
Correct Answer: Metoclopramide
Q16. A clinically important pharmacokinetic interaction of aprepitant is:
- Aprepitant is a moderate CYP3A4 inhibitor and substrate, altering levels of dexamethasone and oral contraceptives
- Aprepitant is a potent P-glycoprotein inducer reducing erythromycin levels
- Aprepitant irreversibly inhibits monoamine oxidase increasing tyramine risk
- Aprepitant enhances renally excreted drugs by blocking OCT2 transporters
Correct Answer: Aprepitant is a moderate CYP3A4 inhibitor and substrate, altering levels of dexamethasone and oral contraceptives
Q17. Which antiemetic is frequently used intravenously in acute migraine to treat headache-associated nausea and may also enhance response to triptans?
- Metoclopramide
- Granisetron
- Fosaprepitant
- Scopolamine
Correct Answer: Metoclopramide
Q18. Which adverse endocrine effect is associated with both metoclopramide and domperidone due to dopamine blockade?
- Hyperprolactinemia leading to galactorrhea and gynecomastia
- Severe hypothyroidism from TSH suppression
- Adrenal insufficiency through ACTH suppression
- Hyperaldosteronism causing hypokalemia
Correct Answer: Hyperprolactinemia leading to galactorrhea and gynecomastia
Q19. The most appropriate prophylactic treatment for motion sickness on a long sea voyage is:
- Transdermal scopolamine patch
- Orbital ondansetron drops
- High-dose aprepitant tablets daily
- Oral erythromycin timed before meals
Correct Answer: Transdermal scopolamine patch
Q20. Which prokinetic agent is contraindicated in mechanical small-bowel obstruction because it can exacerbate obstruction and risk perforation?
- Bethanechol
- Ondansetron
- Aprepitant
- Scopolamine
Correct Answer: Bethanechol
