Sulfones – Dapsone – chemistry and mechanism MCQs With Answer

Sulfones – Dapsone – chemistry and mechanism MCQs With Answer

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Sulfones – Dapsone – chemistry and mechanism MCQs With Answer

Sulfones and dapsone are essential topics in medicinal chemistry and pharmacology for B.Pharm students. This introduction covers sulfone structure, synthesis approaches, spectral identification, pharmacokinetics, metabolic pathways (N‑acetylation and N‑hydroxylation), mechanism of action (competitive inhibition of dihydropteroate synthase and neutrophil oxidative pathways), clinical uses (leprosy, dermatitis herpetiformis, Pneumocystis prophylaxis), adverse effects (hemolysis, methemoglobinemia, hypersensitivity), resistance mechanisms and analytical assays (HPLC, IR features). The following questions reinforce understanding of chemistry, mechanism, safety monitoring and formulation considerations relevant to sulfones and dapsone. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the chemical name of dapsone?

  • 4,4′-diaminodiphenyl sulfone
  • para-aminobenzoic acid
  • sulfanilamide
  • p-aminobenzenesulfonyl chloride

Correct Answer: 4,4′-diaminodiphenyl sulfone

Q2. Which functional group defines sulfones?

  • Sulfonyl group (-SO2-)
  • Sulfhydryl group (-SH)
  • Sulfoxide group (-S=O)
  • Sulfate group (-SO4-)

Correct Answer: Sulfonyl group (-SO2-)

Q3. The primary antibacterial mechanism of dapsone involves inhibition of which enzyme?

  • Dihydropteroate synthase
  • Dihydrofolate reductase
  • DNA gyrase
  • Peptidyl transferase

Correct Answer: Dihydropteroate synthase

Q4. Besides antimicrobial action, dapsone exerts anti‑inflammatory effects by inhibiting which process?

  • Neutrophil myeloperoxidase activity and respiratory burst
  • Cyclooxygenase-2 (COX-2) enzyme
  • Lipoxygenase pathway exclusively
  • TNF-alpha production only

Correct Answer: Neutrophil myeloperoxidase activity and respiratory burst

Q5. Which adverse effect is most characteristically associated with dapsone therapy?

  • Methemoglobinemia
  • Ototoxicity
  • Hyperglycemia
  • Renal tubular necrosis

Correct Answer: Methemoglobinemia

Q6. Which metabolic pathway produces the hydroxylamine metabolite implicated in dapsone toxicity?

  • N‑hydroxylation mediated by cytochrome P450 enzymes
  • Glucuronidation via UGT enzymes
  • Sulfation by sulfotransferases
  • Direct renal oxidation

Correct Answer: N‑hydroxylation mediated by cytochrome P450 enzymes

Q7. Genetic polymorphism of which enzyme system influences dapsone acetylation and plasma levels?

  • N‑acetyltransferase 2 (NAT2)
  • CYP3A4
  • Monoamine oxidase (MAO)
  • Glutathione S‑transferase (GST)

Correct Answer: N‑acetyltransferase 2 (NAT2)

Q8. In leprosy multidrug therapy, dapsone is commonly combined with which two drugs?

  • Rifampicin and clofazimine
  • Streptomycin and isoniazid
  • Ethambutol and pyrazinamide
  • Penicillin and gentamicin

Correct Answer: Rifampicin and clofazimine

Q9. Dapsone therapy is relatively contraindicated in patients with which enzymatic deficiency?

  • Glucose‑6‑phosphate dehydrogenase (G6PD) deficiency
  • Acetyl‑CoA carboxylase deficiency
  • Phenylalanine hydroxylase deficiency
  • Succinyl CoA synthetase deficiency

Correct Answer: Glucose‑6‑phosphate dehydrogenase (G6PD) deficiency

Q10. Resistance to dapsone in Mycobacterium leprae is most commonly due to mutations in which gene?

  • folP1 (dihydropteroate synthase gene)
  • rpoB (RNA polymerase gene)
  • katG (catalase‑peroxidase gene)
  • gyrA (DNA gyrase gene)

Correct Answer: folP1 (dihydropteroate synthase gene)

Q11. In IR spectroscopy, which characteristic absorptions indicate the sulfone group?

  • Strong S=O stretching bands near ~1300 and ~1150 cm-1
  • Broad O–H stretch at 3400 cm-1
  • N–H bending at 1620 cm-1
  • S–H stretch at 2550 cm-1

Correct Answer: Strong S=O stretching bands near ~1300 and ~1150 cm-1

Q12. Which statement best describes dapsone solubility?

  • Poorly soluble in water, more soluble in organic solvents
  • Highly soluble in water at physiological pH
  • Completely insoluble in organic solvents
  • Soluble only in acidic aqueous media

Correct Answer: Poorly soluble in water, more soluble in organic solvents

Q13. Which analytical technique is commonly used for quantitative assay of dapsone in formulations and plasma?

  • High performance liquid chromatography (HPLC)
  • Polarimetry
  • Flame photometry
  • Capillary electrophoresis without detection

Correct Answer: High performance liquid chromatography (HPLC)

Q14. The structural feature of dapsone includes which of the following?

  • Two para‑amino groups on a diphenyl sulfone scaffold
  • A β‑lactam ring fused to a sulfone
  • A single aliphatic amine attached to a sulfoxide
  • A thiol group attached to a benzene ring

Correct Answer: Two para‑amino groups on a diphenyl sulfone scaffold

Q15. Besides leprosy and dermatitis herpetiformis, dapsone is used prophylactically against which pathogen?

  • Pneumocystis jirovecii (in immunocompromised patients)
  • Staphylococcus aureus (MRSA) solely
  • Clostridioides difficile exclusively
  • HSV-1 (herpes simplex)

Correct Answer: Pneumocystis jirovecii (in immunocompromised patients)

Q16. Typical elimination half‑life of dapsone in adults is approximately:

  • About 20–30 hours
  • Less than 1 hour
  • 3–5 minutes
  • More than 200 hours

Correct Answer: About 20–30 hours

Q17. Dapsone hypersensitivity syndrome is best characterized as which type of reaction?

  • Idiosyncratic immune‑mediated reaction with systemic symptoms
  • Classic type I immediate IgE‑mediated anaphylaxis only
  • Local contact dermatitis without systemic signs
  • Dose‑dependent cholestatic hepatitis only

Correct Answer: Idiosyncratic immune‑mediated reaction with systemic symptoms

Q18. Dapsone competes with which substrate at dihydropteroate synthase?

  • Para‑aminobenzoic acid (PABA)
  • Tetrahydrofolate directly
  • Nicotinamide adenine dinucleotide (NADH)
  • ATP

Correct Answer: Para‑aminobenzoic acid (PABA)

Q19. The primary route of elimination for dapsone is:

  • Hepatic metabolism with renal excretion of metabolites
  • Unchanged drug excreted primarily in feces
  • Complete pulmonary elimination as CO2
  • Excretion unchanged through sweat glands

Correct Answer: Hepatic metabolism with renal excretion of metabolites

Q20. Which coexisting condition increases the risk of severe hemolysis when dapsone is given?

  • Glucose‑6‑phosphate dehydrogenase deficiency
  • Hyperthyroidism
  • Myasthenia gravis
  • Essential thrombocythemia

Correct Answer: Glucose‑6‑phosphate dehydrogenase deficiency

Q21. Which laboratory test is most important to monitor during long‑term dapsone therapy?

  • Complete blood count (CBC) including hemoglobin and reticulocyte count
  • Fasting blood glucose only
  • Serum amylase exclusively
  • Serum creatine kinase only

Correct Answer: Complete blood count (CBC) including hemoglobin and reticulocyte count

Q22. A common preparative route for aromatic sulfones like dapsone involves which general chemical transformation?

  • Sulfonylation of aromatic amines followed by appropriate reductions or substitutions
  • Direct alkylation of aliphatic alcohols only
  • Radical polymerization of styrene
  • Electrochemical deposition onto metal surfaces

Correct Answer: Sulfonylation of aromatic amines followed by appropriate reductions or substitutions

Q23. Relative to sulfides, sulfones are generally:

  • More electron‑withdrawing and more polar
  • More nucleophilic
  • Less polar and more basic
  • Indistinguishable in electronic properties

Correct Answer: More electron‑withdrawing and more polar

Q24. Dapsone’s antimicrobial action results in inhibition of folate synthesis leading to decreased synthesis of which cellular component?

  • Thymidine monophosphate required for DNA synthesis
  • Cholesterol in the bacterial membrane
  • Peptidoglycan crosslinking only
  • Ribosomal RNA methylation

Correct Answer: Thymidine monophosphate required for DNA synthesis

Q25. Dapsone is primarily used to treat infections caused by which organism?

  • Mycobacterium leprae
  • Pseudomonas aeruginosa only
  • Herpes simplex virus
  • Candida albicans exclusively

Correct Answer: Mycobacterium leprae

Q26. In dermatology, which condition is a classic indication for dapsone therapy?

  • Dermatitis herpetiformis
  • Psoriasis vulgaris exclusively
  • Alopecia areata only
  • Acne vulgaris as first‑line monotherapy

Correct Answer: Dermatitis herpetiformis

Q27. Which of the following is NOT a common adverse effect of dapsone?

  • Ototoxicity with hearing loss
  • Hemolytic anemia
  • Methemoglobinemia
  • Hypersensitivity syndrome

Correct Answer: Ototoxicity with hearing loss

Q28. Which metabolite of dapsone is primarily responsible for methemoglobinemia and hemolytic effects?

  • Dapsone hydroxylamine metabolite
  • Dapsone glucuronide conjugate
  • Dapsone sulfate conjugate
  • Unchanged parent drug only

Correct Answer: Dapsone hydroxylamine metabolite

Q29. To reduce the risk of severe adverse reactions, which monitoring or preventive step is recommended before starting dapsone?

  • Screen for G6PD deficiency and baseline CBC
  • Obtain an echocardiogram in all patients
  • Initiate simultaneous high‑dose corticosteroids routinely
  • Administer live vaccines immediately before therapy

Correct Answer: Screen for G6PD deficiency and baseline CBC

Q30. Co‑administration of dapsone with other oxidant drugs may increase the risk of which complication?

  • Enhanced hemolysis and methemoglobinemia
  • Reduced antihypertensive effect only
  • Increased bone density
  • Hypoglycemia exclusively

Correct Answer: Enhanced hemolysis and methemoglobinemia

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