Loperamide hydrochloride MCQs With Answer

Loperamide hydrochloride MCQs With Answer: This focused guide provides B.Pharm students with 50 carefully designed multiple-choice questions covering loperamide hydrochloride — an OTC antidiarrheal agent. Questions emphasize mechanism of action, pharmacodynamics, pharmacokinetics, dosing, adverse effects, drug interactions (CYP3A4, P-gp), overdose management, and regulatory and clinical considerations. Each MCQ includes clear answer statements to reinforce concepts relevant to pharmacy practice, therapeutics, and formulation science. Ideal for exam preparation, revision, and classroom quizzes, these MCQs target high-yield facts such as peripheral μ-opioid receptor activity, low oral bioavailability, risks of QT prolongation with high-dose misuse, and contraindications in infectious diarrhea. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which receptor is primarily responsible for loperamide’s antidiarrheal effect?

• Histamine H1 receptor agonism
• Peripheral μ-opioid receptor agonism
• GABA-A receptor modulation
• 5-HT3 receptor antagonism

Correct Answer: Peripheral μ-opioid receptor agonism

Q2. Loperamide reduces diarrhea mainly by which mechanism?

• Increasing intestinal secretion of chloride
• Stimulating bowel motility
• Decreasing intestinal motility and prolonging transit time
• Enhancing mucosal absorption of sodium

Correct Answer: Decreasing intestinal motility and prolonging transit time

Q3. Which transport protein limits loperamide penetration into the central nervous system at therapeutic doses?

• OATP1B1
• MRP2
• P-glycoprotein (P-gp)
• BCRP

Correct Answer: P-glycoprotein (P-gp)

Q4. Loperamide is primarily metabolized by which cytochrome P450 enzymes?

• CYP2D6 and CYP1A2
• CYP3A4 and CYP2C8
• CYP2C19 and CYP2E1
• CYP1A2 and CYP2B6

Correct Answer: CYP3A4 and CYP2C8

Q5. What is a common adverse effect of therapeutic-dose loperamide?

• Torsades de pointes in all patients
• Constipation
• Severe hepatotoxicity
• Acute pancreatitis

Correct Answer: Constipation

Q6. Which condition is a contraindication to loperamide use?

• Traveler’s diarrhea without fever
• Acute dysentery with blood in stools
• Chronic functional diarrhea
• Non-infective osmotic diarrhea

Correct Answer: Acute dysentery with blood in stools

Q7. The typical over-the-counter (OTC) maximum daily dose of loperamide for adults is:

• 2 mg per day
• 8 mg per day
• 24 mg per day
• 40 mg per day

Correct Answer: 8 mg per day

Q8. Which formulation types are commonly available for loperamide?

• Injectable and transdermal patch
• Oral tablets, capsules, and oral solution
• Inhalation powder and nasal spray
• Topical cream and eye drops

Correct Answer: Oral tablets, capsules, and oral solution

Q9. A key safety concern with high-dose loperamide misuse is:

• Renal stone formation
• Severe QT interval prolongation and ventricular arrhythmia
• White blood cell suppression
• Hypoglycemia

Correct Answer: Severe QT interval prolongation and ventricular arrhythmia

Q10. In cases of loperamide-induced respiratory depression or opioid-like toxicity, which antidote is used?

• Flumazenil
• Naloxone
• Atropine
• Vitamin K

Correct Answer: Naloxone

Q11. Why is loperamide oral bioavailability very low?

• Extensive gastrointestinal degradation by acid
• High first-pass metabolism and P-gp efflux
• Poor dissolution in stomach acid
• Rapid renal excretion before absorption

Correct Answer: High first-pass metabolism and P-gp efflux

Q12. Loperamide’s primary site of action in the gastrointestinal tract is:

• Luminal surface of the small intestinal epithelium
• Enteric nervous system (myenteric plexus)
• Peyer’s patches immune cells
• Pancreatic exocrine cells

Correct Answer: Enteric nervous system (myenteric plexus)

Q13. Which patient population has an FDA warning against loperamide use under age-specific limits?

• Adults over 65 years
• Children under 2 years
• Adolescents aged 12–17 years
• Pregnant women in third trimester only

Correct Answer: Children under 2 years

Q14. Which drug interaction increases systemic loperamide exposure and risk of central/peripheral toxicity?

• Rifampin (CYP inducer)
• Ketoconazole (CYP3A4 and P-gp inhibitor)
• Metformin (renal elimination unaffected)
• Amoxicillin (no major interaction)

Correct Answer: Ketoconazole (CYP3A4 and P-gp inhibitor)

Q15. Loperamide is chemically classified as a:

• Benzoquinone antibiotic
• Synthetic piperidine opioid derivative
• Catecholamine agonist
• Macrolide

Correct Answer: Synthetic piperidine opioid derivative

Q16. For hospital management of severe loperamide-related cardiotoxicity, which immediate measure is recommended?

• Administer activated charcoal only
• Cardiac monitoring and electrolyte correction
• IV ceftriaxone
• Immediate peritoneal dialysis

Correct Answer: Cardiac monitoring and electrolyte correction

Q17. The onset of action of oral loperamide is typically:

• Within 5–10 minutes
• 1–3 hours
• 24–48 hours
• After 7 days of administration

Correct Answer: 1–3 hours

Q18. Loperamide’s duration of antidiarrheal effect after a single dose is approximately:

• 30 minutes
• 2–4 hours
• Up to 24 hours
• 7–10 days

Correct Answer: Up to 24 hours

Q19. Which laboratory finding would most likely be sought before administering loperamide in a patient with suspected cardiac risk?

• Serum amylase
• Electrocardiogram (ECG) for QT interval
• Arterial blood gas for oxygenation
• Complete blood count for anemia

Correct Answer: Electrocardiogram (ECG) for QT interval

Q20. Compared to diphenoxylate, loperamide has which characteristic?

• Greater central opioid effects at normal doses
• Less central penetration due to P-gp activity
• Higher abuse potential at OTC doses
• Primarily cholinergic mechanism

Correct Answer: Less central penetration due to P-gp activity

Q21. Loperamide’s effect on intestinal secretion is best described as:

• Strongly secretory by increasing chloride release
• Primarily motility reduction with modest reduction in secretion
• Major pro-absorptive stimulant of sodium-glucose cotransport
• Major inhibition of bile acid secretion

Correct Answer: Primarily motility reduction with modest reduction in secretion

Q22. Which statement about loperamide pharmacokinetics is true?

• It has near 100% oral bioavailability.
• It undergoes significant hepatic first-pass metabolism.
• It is excreted unchanged exclusively via kidneys.
• It is not a substrate for transport proteins.

Correct Answer: It undergoes significant hepatic first-pass metabolism.

Q23. In pregnancy, loperamide is generally classified as which risk category (historically)?

• Category A
• Category B
• Category C
• Category X

Correct Answer: Category C

Q24. The greatest risk factor for severe cardiotoxicity with loperamide is:

• Concurrent use of CYP3A4 and P-gp inhibitors and high-dose misuse
• Taking the drug with high-fat meal
• Using the drug in children over 12 years
• Switching from tablet to capsule form

Correct Answer: Concurrent use of CYP3A4 and P-gp inhibitors and high-dose misuse

Q25. Which clinical use is an FDA-accepted indication for loperamide?

• Treatment of bacterial sepsis
• Symptomatic management of acute nonspecific diarrhea
• First-line therapy for inflammatory bowel disease
• Prevention of traveler’s diarrhea by prophylactic daily dosing indefinitely

Correct Answer: Symptomatic management of acute nonspecific diarrhea

Q26. Which of the following best explains loperamide’s low central nervous system effects at therapeutic doses?

• It is rapidly metabolized to inactive metabolites in the brain.
• Efflux by P-gp at the blood-brain barrier prevents CNS accumulation.
• It is too polar to cross the blood-brain barrier at any dose.
• It selectively binds to peripheral receptors only.

Correct Answer: Efflux by P-gp at the blood-brain barrier prevents CNS accumulation.

Q27. What monitoring is most important when a patient on loperamide is also prescribed a strong CYP3A4 inhibitor?

• Periodic liver ultrasound
• Monitoring for signs of opioid toxicity and cardiac arrhythmia
• Daily complete blood counts
• Urine glucose monitoring

Correct Answer: Monitoring for signs of opioid toxicity and cardiac arrhythmia

Q28. Loperamide abuse for opioid-like effects typically requires:

• Standard OTC dosing for several days
• Very high doses often combined with P-gp inhibitors
• Topical application to mucous membranes
• Co-administration with antacids only

Correct Answer: Very high doses often combined with P-gp inhibitors

Q29. The primary route of elimination for loperamide and its metabolites is:

• Renal excretion of unchanged drug
• Fecal excretion
• Exhalation via lungs
• Sweat and saliva

Correct Answer: Fecal excretion

Q30. Which symptom indicates potentially serious loperamide overdose requiring urgent care?

• Mild dry mouth
• Profound dizziness, syncope, or palpitations
• Transient hiccups
• Passing gas

Correct Answer: Profound dizziness, syncope, or palpitations

Q31. For pharmacy counseling, what key advice should be given to patients taking loperamide for acute diarrhea?

• Continue using indefinitely until symptoms disappear
• Stop use and seek medical care if fever or bloody stools develop
• Double the dose if no effect in one hour
• Avoid fluids while taking the drug

Correct Answer: Stop use and seek medical care if fever or bloody stools develop

Q32. Loperamide dosing for adults (initial) is commonly recommended as:

• 8 mg initial dose followed by 8 mg hourly
• 4 mg initially, then 2 mg after each loose stool
• 0.1 mg once daily
• 50 mg every 6 hours

Correct Answer: 4 mg initially, then 2 mg after each loose stool

Q33. Which laboratory test would be most informative after suspected massive loperamide ingestion?

• Serum troponin and ECG
• Serum ceruloplasmin
• Serum amylase only
• Thyroid function tests

Correct Answer: Serum troponin and ECG

Q34. Which mechanism contributes to loperamide’s anti-secretory effects?

• Activation of enteric nitric oxide synthase
• Inhibition of acetylcholine release from enteric neurons
• Stimulation of prostaglandin E2 secretion
• Direct blockade of epithelial chloride channels

Correct Answer: Inhibition of acetylcholine release from enteric neurons

Q35. Which statement about loperamide use in infectious diarrhea is correct?

• Always indicated for invasive bacterial diarrhea to reduce transmission
• Contraindicated in suspected Clostridioides difficile infection
• First-line monotherapy for all cases of salmonella gastroenteritis
• Should be used without antibiotics in dysentery

Correct Answer: Contraindicated in suspected Clostridioides difficile infection

Q36. A formulation advantage of the oral solution of loperamide is:

• Eliminates need for hepatic metabolism
• Allows flexible dosing for children and dysphagia patients
• Prevents all drug interactions
• Delivers drug intravenously

Correct Answer: Allows flexible dosing for children and dysphagia patients

Q37. Which pharmacodynamic property explains why loperamide can increase anal sphincter tone?

• Anticholinergic blockade in intestinal smooth muscle
• Peripheral opioid-mediated increase in sphincter contraction
• Beta-adrenergic agonism in sphincter muscles
• Local anesthetic action on sphincter nerves

Correct Answer: Peripheral opioid-mediated increase in sphincter contraction

Q38. In a patient with severe hepatic impairment, loperamide dosing considerations include:

• No adjustment; loperamide is renally cleared only
• Use with caution and consider dose reduction due to reduced metabolism
• Double the dose because of increased clearance
• Avoid monitoring for adverse effects

Correct Answer: Use with caution and consider dose reduction due to reduced metabolism

Q39. Which laboratory or clinical test helps assess risk prior to giving loperamide to a cardiac patient?

• Baseline ECG for conduction abnormalities
• Sputum culture
• Bone density scan
• Urinalysis for protein

Correct Answer: Baseline ECG for conduction abnormalities

Q40. Loperamide is most appropriately used for which of the following scenarios?

• Diarrhea with high fever and severe abdominal pain suggestive of invasive infection
• Short-term symptomatic relief of non-bloody acute watery diarrhea
• Chronic constipation management
• Eradication of Giardia lamblia as monotherapy

Correct Answer: Short-term symptomatic relief of non-bloody acute watery diarrhea

Q41. Which structural feature is true about loperamide?

• It is a small polar peptide
• It contains a piperidine ring characteristic of many opioids
• It is an inorganic salt with no carbon
• It is a monosaccharide derivative

Correct Answer: It contains a piperidine ring characteristic of many opioids

Q42. Which of the following is a correct counseling point regarding missed doses of loperamide for acute diarrhea?

• Double the next dose to compensate
• Skip the missed dose and continue as directed
• Stop therapy permanently
• Immediately visit emergency department

Correct Answer: Skip the missed dose and continue as directed

Q43. What is a potential pharmacokinetic effect when loperamide is co-administered with rifampin?

• Increased loperamide plasma levels due to P-gp inhibition
• Decreased loperamide exposure due to CYP induction
• Immediate renal elimination of loperamide
• No change in loperamide pharmacokinetics

Correct Answer: Decreased loperamide exposure due to CYP induction

Q44. How does P-gp inhibition alter loperamide toxicity risk?

• P-gp inhibition reduces systemic exposure and toxicity
• P-gp inhibition permits increased CNS access and systemic accumulation, increasing toxicity
• P-gp inhibition has no effect on loperamide disposition
• P-gp inhibition converts loperamide to inactive metabolites

Correct Answer: P-gp inhibition permits increased CNS access and systemic accumulation, increasing toxicity

Q45. Which of the following signs would suggest ileus as an adverse effect of loperamide?

• Increased bowel sounds and watery stools
• Abdominal distension, absent bowel sounds, and severe constipation
• Frequent flatulence and urgency
• Rapid weight loss

Correct Answer: Abdominal distension, absent bowel sounds, and severe constipation

Q46. Loperamide should be avoided in patients with which bacterial infection due to risk of worsening disease?

• E. coli non-invasive traveler’s diarrhea
• Clostridioides difficile infection
• Viral gastroenteritis from norovirus
• Food allergy–related diarrhea

Correct Answer: Clostridioides difficile infection

Q47. Which educational point is important regarding loperamide and driving or operating machinery?

• Loperamide always causes profound sedation, so avoid all activities
• Although CNS effects are rare at therapeutic doses, caution is advised if dizziness occurs
• No caution needed; it improves alertness
• It enhances reflexes and is safe

Correct Answer: Although CNS effects are rare at therapeutic doses, caution is advised if dizziness occurs

Q48. In pharmacology exams, loperamide is often contrasted with other antidiarrheals because it:

• Is the only opioid that crosses the BBB freely
• Has strong anti-secretory antibacterial properties
• Produces antidiarrheal effects largely via opioid receptors without significant analgesia at recommended doses
• Is a first-line antibiotic for travelers’ diarrhea

Correct Answer: Produces antidiarrheal effects largely via opioid receptors without significant analgesia at recommended doses

Q49. When counseling on storage and disposal of loperamide products, pharmacy guidance should include:

• Store in refrigerator and flush unused tablets down the toilet
• Keep at room temperature, away from children, and dispose of expired product per local regulations
• Keep containers open to air to prevent moisture
• Transfer pills to unlabeled containers for convenience

Correct Answer: Keep at room temperature, away from children, and dispose of expired product per local regulations

Q50. For B.Pharm students studying loperamide, a high-yield exam topic is:

• The role of loperamide in treating systemic fungal infections
• Its interaction with CYP3A4/P-gp and implications for cardiotoxicity in overdose
• The superiority of loperamide over antibiotics for bacterial meningitis
• Its use as an immunosuppressant in transplant patients

Correct Answer: Its interaction with CYP3A4/P-gp and implications for cardiotoxicity in overdose

G S Sachin

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.

Mail- Sachin@pharmacyfreak.com