Introduction: Drugs for constipation encompass a range of laxatives and prokinetic agents classified by mechanism: bulk-forming, stool softeners, osmotic, stimulant, lubricant, chloride channel activators, guanylate cyclase‑C agonists, peripherally acting μ‑opioid receptor antagonists (PAMORAs), and prokinetics. B. Pharm students must understand classification, mechanisms of action, clinical uses, onset of action, adverse effects (electrolyte imbalance, cramping, dependence, hypermagnesemia), contraindications (bowel obstruction, perforation), and specific drug examples such as psyllium, docusate, lactulose, polyethylene glycol, bisacodyl, senna, lubiprostone, linaclotide, naloxegol and methylnaltrexone. This knowledge aids safe prescribing, counseling and formulation development. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which class of laxatives increases fecal bulk by absorbing water and forming a gel, thereby stimulating peristalsis?
- Osmotic laxatives
- Bulk‑forming laxatives
- Stimulant laxatives
- Stool softeners
Correct Answer: Bulk‑forming laxatives
Q2. Which of the following is a commonly used osmotic laxative for chronic constipation with a delayed onset of action (12–72 hours)?
- Bisacodyl
- Polyethylene glycol (PEG)
- Docusate sodium
- Sennosides
Correct Answer: Polyethylene glycol (PEG)
Q3. Which laxative acts by stimulating enteric neurons and increasing fluid secretion and motility, often causing abdominal cramping?
- Senna (sennosides)
- Mineral oil
- Psyllium husk
- Lactulose
Correct Answer: Senna (sennosides)
Q4. Which agent is a stool softener that lowers surface tension to allow water penetration into stool?
- Docusate sodium
- Lubiprostone
- Magnesium citrate
- Prucalopride
Correct Answer: Docusate sodium
Q5. Lubiprostone relieves constipation primarily by which mechanism?
- Activation of chloride channels (ClC‑2) to increase intestinal fluid secretion
- Inhibition of opioid receptors in the gut
- Bulk formation by absorbing water
- Stimulation of mucosal 5‑HT4 receptors
Correct Answer: Activation of chloride channels (ClC‑2) to increase intestinal fluid secretion
Q6. Linaclotide treats chronic constipation by which mechanism?
- Guanylate cyclase‑C agonism increasing cGMP and intestinal secretion
- Peripheral μ‑opioid receptor antagonism
- Sodium retention in enterocytes
- Direct cholinergic stimulation of smooth muscle
Correct Answer: Guanylate cyclase‑C agonism increasing cGMP and intestinal secretion
Q7. Which laxative is contraindicated in patients with suspected intestinal obstruction due to risk of perforation?
- Psyllium
- Bisacodyl suppository
- Mineral oil enema
- All of the above
Correct Answer: All of the above
Q8. Which osmotic laxative can cause hypermagnesemia in patients with renal impairment?
- Magnesium sulfate/citrate
- Polyethylene glycol
- Lactulose
- Psyllium
Correct Answer: Magnesium sulfate/citrate
Q9. Which class is most appropriate for short‑term relief of opioid‑induced constipation without reversing central analgesia?
- Bulk‑forming laxatives
- Peripherally acting μ‑opioid receptor antagonists (PAMORAs)
- Systemic opioid antagonists (e.g., naloxone oral)
- Mineral oil
Correct Answer: Peripherally acting μ‑opioid receptor antagonists (PAMORAs)
Q10. Which drug is an example of a PAMORA used for opioid‑induced constipation?
- Methylnaltrexone
- Bisacodyl
- Linaclotide
- Lactulose
Correct Answer: Methylnaltrexone
Q11. Which laxative is preferred for bowel preparation prior to colonoscopy due to potent osmotic effect and predictable cleansing?
- Polyethylene glycol (large volume) solution
- Psyllium husk
- Docusate sodium
- Mineral oil
Correct Answer: Polyethylene glycol (large volume) solution
Q12. Which adverse effect is classically associated with chronic stimulant laxative (senna, bisacodyl) overuse?
- Melanosis coli and potential cathartic dependence
- Hyperkalemia
- Hypersalivation
- Ototoxicity
Correct Answer: Melanosis coli and potential cathartic dependence
Q13. Which laxative is safe and commonly used in pregnancy for constipation?
- Psyllium (bulk‑forming fiber)
- Lubiprostone
- Methylnaltrexone
- Bisacodyl suppositories routinely
Correct Answer: Psyllium (bulk‑forming fiber)
Q14. Lactulose relieves constipation by what primary mechanism?
- Osmotic retention of water and colonic fermentation to acids
- Direct activation of chloride channels
- Binding bile acids to stimulate secretion
- Acting as a stool surfactant
Correct Answer: Osmotic retention of water and colonic fermentation to acids
Q15. Which prokinetic 5‑HT4 agonist is used for chronic constipation and increases colonic motility?
- Prucalopride
- Lubiprostone
- Linaclotide
- Magnesium hydroxide
Correct Answer: Prucalopride
Q16. Mineral oil acts as a lubricant laxative by which action?
- Coating stool to reduce water absorption and ease passage
- Increasing fecal bulk via fiber content
- Inhibiting sodium channels in enterocytes
- Stimulating bile acid secretion
Correct Answer: Coating stool to reduce water absorption and ease passage
Q17. Which laxative type is least appropriate for long‑term use due to risk of electrolyte disturbances and dependence?
- Bulk‑forming laxatives
- Osmotic laxatives like PEG
- Stimulant laxatives like bisacodyl and senna
- Stool softeners
Correct Answer: Stimulant laxatives like bisacodyl and senna
Q18. Which drug increases intracellular and extracellular cyclic GMP in enterocytes via guanylate cyclase‑C and is contraindicated in children under 6?
- Linaclotide
- Lubiprostone
- Methylnaltrexone
- Docusate
Correct Answer: Linaclotide
Q19. A B. Pharm student is counseling on PEG powder for constipation. What is an accurate counseling point?
- PEG is systemically absorbed and causes sedation
- PEG works by osmotic retention, is minimally absorbed, and onset is 1–3 days
- PEG should never be used before colonoscopy
- PEG acts as a stimulant on enteric nerves
Correct Answer: PEG works by osmotic retention, is minimally absorbed, and onset is 1–3 days
Q20. Which combination of drugs would most likely increase risk of electrolyte imbalance when used together aggressively?
- Psyllium + docusate
- Lactulose + magnesium citrate
- Linaclotide + lubiprostone
- Methylnaltrexone + naloxegol
Correct Answer: Lactulose + magnesium citrate
Q21. Which laxative is indicated for hepatic encephalopathy as well as constipation?
- Lactulose
- Bisacodyl
- Psyllium
- Prucalopride
Correct Answer: Lactulose
Q22. Which laxative can interfere with absorption of fat‑soluble vitamins with chronic use?
- Mineral oil
- Polyethylene glycol
- Prucalopride
- Metoclopramide
Correct Answer: Mineral oil
Q23. Naloxegol differs from naloxone in that naloxegol:
- Crosses the blood‑brain barrier causing central opioid reversal
- Is a polyethylene glycol conjugate that limits central penetration, acting peripherally
- Is a bulk‑forming laxative
- Is a chloride channel activator
Correct Answer: Is a polyethylene glycol conjugate that limits central penetration, acting peripherally
Q24. Which laxative class is most effective for patients with low fluid intake and requires adequate water to avoid intestinal obstruction?
- Bulk‑forming laxatives (psyllium)
- Saline laxatives
- Stimulant laxatives
- Chloride channel activators
Correct Answer: Bulk‑forming laxatives (psyllium)
Q25. Bisacodyl’s primary mechanism of action involves:
- Hydrophilic gel formation in the colon
- Direct stimulation of enteric nerves and colon smooth muscle
- Activation of guanylate cyclase‑C
- Peripheral opioid receptor blockade
Correct Answer: Direct stimulation of enteric nerves and colon smooth muscle
Q26. Which adverse effect is most commonly associated with linaclotide and lubiprostone?
- Constipation worsening
- Diarrhea
- Bradycardia
- Urinary retention
Correct Answer: Diarrhea
Q27. For elderly patients prone to dehydration, which laxative class is generally safest?
- Saline laxatives
- Bulk‑forming laxatives with adequate fluid intake
- Stimulant laxatives daily
- Mineral oil long‑term
Correct Answer: Bulk‑forming laxatives with adequate fluid intake
Q28. Which of the following is NOT a correct pairing of drug and classification?
- Psyllium – Bulk‑forming laxative
- Senna – Osmotic laxative
- Polyethylene glycol – Osmotic laxative
- Docusate – Stool softener (emollient)
Correct Answer: Senna – Osmotic laxative
Q29. Which oral agent is used to treat chronic idiopathic constipation by selectively stimulating epithelial Cl‑ channels and is approved for women and men?
- Lubiprostone (approved mainly in women for CIC; limited in men historically)
- Linaclotide (GC‑C agonist approved for CIC in adults)
- Methylnaltrexone
- Mineral oil
Correct Answer: Linaclotide (GC‑C agonist approved for CIC in adults)
Q30. When counseling a patient on stimulant laxative suppositories (bisacodyl), which point is most accurate?
- Suppositories act within minutes to an hour and avoid systemic absorption
- They should be taken with dairy products for effectiveness
- They permanently reset bowel motility with one dose
- They are the first‑line chronic therapy for routine constipation
Correct Answer: Suppositories act within minutes to an hour and avoid systemic absorption
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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