Introduction
Antileprotic drugs dapsone and clofazimine are cornerstone agents in the management of leprosy and form key components of WHO multi‑drug therapy (MDT). This concise guide for B.Pharm students covers mechanism of action, pharmacokinetics, clinical uses, adverse effects such as hemolysis, methemoglobinemia, G6PD considerations, and clofazimine‑induced skin pigmentation. Emphasis is placed on drug interactions, resistance mechanisms, monitoring parameters, dosing in adults and special populations, and adverse‑effect management. Understanding these antileprotic drugs — dapsone and clofazimine — is essential for safe dispensing, patient counselling and rational therapy selection. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which enzyme is primarily inhibited by dapsone, producing its antileprotic effect?
- Dihydrofolate reductase
- Dihydropteroate synthase
- Topoisomerase IV
- RNA polymerase
Correct Answer: Dihydropteroate synthase
Q2. Clofazimine’s antimicrobial action is thought to involve which of the following mechanisms?
- Inhibition of cell wall mycolic acid synthesis
- Binding to mycobacterial DNA and generating reactive oxygen species
- Inhibition of 30S ribosomal subunit
- Blocking folate synthesis
Correct Answer: Binding to mycobacterial DNA and generating reactive oxygen species
Q3. A major hematologic adverse effect of dapsone is:
- Agranulocytosis
- Hemolytic anemia, especially in G6PD deficiency
- Thrombocytopenia
- Pancytopenia
Correct Answer: Hemolytic anemia, especially in G6PD deficiency
Q4. Which metabolite pathway of dapsone is primarily responsible for methemoglobinemia?
- Oxidative N‑hydroxylation producing hydroxylamine metabolites
- Glucuronidation in the liver
- Acetylation to inactive metabolites
- Reduction by intestinal flora
Correct Answer: Oxidative N‑hydroxylation producing hydroxylamine metabolites
Q5. In WHO multidrug therapy for multibacillary leprosy, the recommended monthly supervised dose of clofazimine is:
- 100 mg once monthly
- 300 mg once monthly
- 50 mg once monthly
- 600 mg once monthly
Correct Answer: 300 mg once monthly
Q6. Which of the following adverse effects is most characteristic of clofazimine therapy?
- Grayish‑blue skin discoloration and conjunctival pigmentation
- Severe nephrotoxicity
- Hypoglycemia
- Ototoxicity
Correct Answer: Grayish‑blue skin discoloration and conjunctival pigmentation
Q7. Dapsone is primarily eliminated by which route?
- Renal excretion of unchanged drug
- Hepatic metabolism with renal excretion of metabolites
- Fecal excretion unchanged
- Exhalation as volatile metabolites
Correct Answer: Hepatic metabolism with renal excretion of metabolites
Q8. Which drug commonly used in MDT induces hepatic enzymes and can reduce dapsone plasma levels?
- Rifampicin
- Minocycline
- Ofloxacin
- Ethambutol
Correct Answer: Rifampicin
Q9. A life‑threatening hypersensitivity reaction associated with dapsone characterized by fever, rash, and hepatitis is called:
- Stevens‑Johnson syndrome
- Dapsone hypersensitivity syndrome (DHS)
- Anaphylactic shock
- Serotonin syndrome
Correct Answer: Dapsone hypersensitivity syndrome (DHS)
Q10. Clofazimine’s pharmacokinetic property that most influences prolonged skin discoloration is:
- Low oral bioavailability
- Extensive tissue accumulation and very long half‑life
- Rapid renal clearance
- High first‑pass hepatic metabolism
Correct Answer: Extensive tissue accumulation and very long half‑life
Q11. Which laboratory test is essential before initiating dapsone therapy in at‑risk patients?
- Serum creatinine only
- G6PD activity assay
- Lipid profile
- Thyroid function tests
Correct Answer: G6PD activity assay
Q12. Dapsone is structurally classified as a:
- Sulfonamide antibiotic
- Sulfone antibacterial
- Macrolide antibiotic
- Rifamycin derivative
Correct Answer: Sulfone antibacterial
Q13. Which adverse effect may require immediate discontinuation of dapsone?
- Mild nausea for 2 days
- Onset of jaundice and elevated transaminases
- Transient headache
- Minor skin dryness
Correct Answer: Onset of jaundice and elevated transaminases
Q14. The common daily dose of dapsone for adult leprosy treatment is:
- 10 mg daily
- 100 mg daily
- 500 mg daily
- 1000 mg daily
Correct Answer: 100 mg daily
Q15. Which statement about clofazimine and pregnancy is most accurate?
- Clofazimine is absolutely contraindicated in pregnancy due to teratogenicity proven in humans
- Use only if benefit outweighs risk; it accumulates and may cause fetal pigmentation
- Clofazimine is safe and requires no special precautions in pregnancy
- Clofazimine causes maternal hyperglycemia in pregnancy
Correct Answer: Use only if benefit outweighs risk; it accumulates and may cause fetal pigmentation
Q16. Resistance to dapsone in Mycobacterium leprae commonly arises from mutations in which gene family?
- rpoB gene encoding RNA polymerase
- folP1 gene encoding dihydropteroate synthase
- katG gene encoding catalase‑peroxidase
- gyrA gene encoding DNA gyrase
Correct Answer: folP1 gene encoding dihydropteroate synthase
Q17. Which supportive treatment can be used for significant dapsone‑induced methemoglobinemia?
- High‑dose vitamin C only
- Methylene blue administration
- Immediate hemodialysis
- Intravenous calcium gluconate
Correct Answer: Methylene blue administration
Q18. Clofazimine may cause which gastrointestinal complication with long‑term use?
- Pancreatitis
- Abdominal pain and risk of small intestinal obstruction due to crystal deposition
- Massive upper GI bleeding
- Marked constipation only without severe consequences
Correct Answer: Abdominal pain and risk of small intestinal obstruction due to crystal deposition
Q19. Which monitoring parameter is most relevant during prolonged clofazimine therapy?
- Periodic liver function tests and monitoring for skin discoloration
- Frequent INR monitoring
- Daily blood glucose measurements
- Regular audiometry
Correct Answer: Periodic liver function tests and monitoring for skin discoloration
Q20. For paucibacillary leprosy, the usual WHO MDT regimen includes:
- Rifampicin monthly and dapsone daily for 6 months
- Only clofazimine daily for 12 months
- High‑dose isoniazid daily for 3 months
- Rifampicin and clofazimine daily for 24 months
Correct Answer: Rifampicin monthly and dapsone daily for 6 months
Q21. Which counseling point is important for patients starting clofazimine?
- Expect rapid improvement in 48 hours
- Skin and body fluid discoloration may occur and can be prolonged
- Avoid dairy products while taking the drug
- Double the dose if a dose is missed
Correct Answer: Skin and body fluid discoloration may occur and can be prolonged
Q22. Which adverse effect is a dose‑related concern with high doses of dapsone?
- Peripheral neuropathy similar to isoniazid
- Methemoglobinemia and hemolysis
- Ototoxicity
- Hypotension
Correct Answer: Methemoglobinemia and hemolysis
Q23. Which property of clofazimine affects its bioavailability and leads to variable absorption?
- High water solubility
- Extremely lipophilic nature and dependence on fat intake
- Rapid gastric degradation
- Extensive renal excretion
Correct Answer: Extremely lipophilic nature and dependence on fat intake
Q24. Which drug interaction concern is relevant when combining dapsone with drugs that are CYP inducers?
- CYP inducers decrease dapsone levels, potentially reducing efficacy
- CYP inducers increase dapsone levels, increasing toxicity
- No interaction is expected with CYP modulators
- CYP inducers cause immediate allergic reactions with dapsone
Correct Answer: CYP inducers decrease dapsone levels, potentially reducing efficacy
Q25. Which patient factor increases risk of severe hemolysis when prescribing dapsone?
- History of peptic ulcer disease
- Glucose‑6‑phosphate dehydrogenase (G6PD) deficiency
- Hyperthyroidism
- Concurrent statin therapy
Correct Answer: Glucose‑6‑phosphate dehydrogenase (G6PD) deficiency
Q26. Which formulation consideration is true for clofazimine tablets used in MDT programs?
- They are given intravenously in most protocols
- Oral tablets are administered and supervised monthly doses are common
- They are formulated as topical creams only
- They must be compounded into liquid form for adults
Correct Answer: Oral tablets are administered and supervised monthly doses are common
Q27. A patient on dapsone develops cyanosis and dark colored blood—this suggests:
- Severe hypoglycemia
- Methemoglobinemia reducing oxygen carrying capacity
- Pulmonary embolism
- Acute myocardial infarction
Correct Answer: Methemoglobinemia reducing oxygen carrying capacity
Q28. Which population should receive careful risk‑benefit assessment before starting dapsone?
- Patients with controlled hypertension
- Patients with known G6PD deficiency or severe anemia
- Patients with seasonal allergy
- Young adults with no comorbidities
Correct Answer: Patients with known G6PD deficiency or severe anemia
Q29. Which of the following is a non‑antimicrobial benefit of clofazimine in leprosy treatment?
- Anti‑inflammatory effects useful for leprosy reactions
- Potent anticoagulant activity
- Hypoglycemic control
- Rapid analgesic effect for neuropathic pain
Correct Answer: Anti‑inflammatory effects useful for leprosy reactions
Q30. In case of dapsone hypersensitivity syndrome, the immediate management step is:
- Continue therapy and add antihistamines
- Stop dapsone immediately and provide supportive care including corticosteroids if needed
- Reduce dose by half and monitor closely
- Switch to topical dapsone formulation
Correct Answer: Stop dapsone immediately and provide supportive care including corticosteroids if needed
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