GIT pharmacology: prokinetics and antiemetics MCQs With Answer

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

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