Antitubercular drugs – classification and mechanism MCQs With Answer

Antitubercular drugs – classification and mechanism MCQs With Answer

Antitubercular drugs are essential in tuberculosis pharmacotherapy; understanding their classification, mechanisms of action, resistance pathways, pharmacokinetics, adverse effects and monitoring is crucial for B. Pharm students. This study set covers first-line agents (isoniazid, rifampicin, pyrazinamide, ethambutol, streptomycin), second-line and newer drugs (fluoroquinolones, aminoglycosides, bedaquiline, linezolid), mechanisms (mycolic acid inhibition, RNA polymerase blockade, ATP synthase inhibition), resistance mutations (katG, rpoB, pncA), and clinical monitoring (LFTs, visual tests, audiometry). Answers are provided to aid self-assessment and exam preparation. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which is the primary classification used for antitubercular drugs in standard treatment protocols?

• First-line and Second-line
• Gram-positive and Gram-negative
• Bacteriocidal and Antiseptic
• Topical and Systemic

Correct Answer: First-line and Second-line

Q2. What is the standard short-course regimen abbreviation for drug-sensitive pulmonary TB?

• 2HRZE/4HR (2 months HRZE followed by 4 months HR)
• 6H (6 months isoniazid monotherapy)
• 9R (9 months rifampicin monotherapy)
• 3EHR (3 months ethambutol, isoniazid, rifampicin)

Correct Answer: 2HRZE/4HR (2 months HRZE followed by 4 months HR)

Q3. Isoniazid primarily inhibits which essential mycobacterial process after activation by KatG?

• Inhibition of mycolic acid synthesis via InhA
• Blockade of DNA gyrase
• Inhibition of RNA polymerase
• Disruption of cell wall arabinogalactan synthesis

Correct Answer: Inhibition of mycolic acid synthesis via InhA

Q4. Rifampicin exerts its bactericidal action by binding to which mycobacterial enzyme?

• DNA-dependent RNA polymerase (rpoB)
• DNA gyrase (gyrA)
• ATP synthase
• 30S ribosomal subunit

Correct Answer: DNA-dependent RNA polymerase (rpoB)

Q5. Pyrazinamide requires conversion by pyrazinamidase to exert activity. In what environment is it most effective?

• Acidic intracellular environments (converted to pyrazinoic acid)
• Alkaline extracellular fluids
• Within biofilms only
• When co-administered with aminoglycosides

Correct Answer: Acidic intracellular environments (converted to pyrazinoic acid)

Q6. Ethambutol inhibits which enzyme involved in cell wall synthesis?

• Arabinosyl transferase (affecting arabinogalactan)
• RNA polymerase
• Enoyl-ACP reductase
• ATP synthase

Correct Answer: Arabinosyl transferase (affecting arabinogalactan)

Q7. Streptomycin, an aminoglycoside, kills mycobacteria by binding to which ribosomal subunit?

• 30S ribosomal subunit causing misreading
• 50S ribosomal subunit blocking peptidyl transferase
• 23S rRNA inhibiting translocation
• 28S subunit inhibiting initiation

Correct Answer: 30S ribosomal subunit causing misreading

Q8. Which first-line antitubercular drug is generally considered bacteriostatic rather than bactericidal?

• Ethambutol
• Isoniazid
• Rifampicin
• Pyrazinamide

Correct Answer: Ethambutol

Q9. Which adverse effect of isoniazid is prevented by co-administration of pyridoxine (vitamin B6)?

• Peripheral neuropathy
• Hepatotoxicity
• Optic neuritis
• Ototoxicity

Correct Answer: Peripheral neuropathy

Q10. Rifampicin causes a major drug interaction by inducing which hepatic system?

• CYP450 enzyme system leading to drug interactions
• UDP-glucuronosyltransferase inhibition only
• Renal tubular secretion enhancement
• Mitochondrial CYP enzymes exclusively

Correct Answer: CYP450 enzyme system leading to drug interactions

Q11. A mutation in which gene is most commonly associated with rifampicin resistance?

• rpoB
• katG
• pncA
• gyrA

Correct Answer: rpoB

Q12. Isoniazid resistance is frequently due to mutation or deletion in which gene affecting activation?

• katG (catalase-peroxidase)
• rpoB
• embB
• pncA

Correct Answer: katG (catalase-peroxidase)

Q13. Resistance to pyrazinamide is commonly mediated by mutations in which gene?

• pncA
• katG
• rpoB
• inhA

Correct Answer: pncA

Q14. Which gene mutation is associated with ethambutol resistance?

• embB
• gyrA
• rpoB
• katG

Correct Answer: embB

Q15. Which laboratory tests are most relevant to monitor during pyrazinamide therapy?

• Serum uric acid and liver function tests
• Serum creatinine only
• Complete blood count only
• Fasting blood glucose and lipid profile

Correct Answer: Serum uric acid and liver function tests

Q16. Which adverse effect requires monitoring of visual acuity and color vision during therapy?

• Ethambutol-associated optic neuritis
• Rifampicin-induced red discoloration
• Isoniazid-related neuropathy
• Pyrazinamide-induced hyperuricemia

Correct Answer: Ethambutol-associated optic neuritis

Q17. Aminoglycosides used in TB (e.g., streptomycin, amikacin) are notable for which toxicities?

• Ototoxicity and nephrotoxicity
• Hepatotoxicity and arthralgia
• Visual disturbances and hyperuricemia
• Bone marrow suppression and anemia

Correct Answer: Ototoxicity and nephrotoxicity

Q18. Fluoroquinolones used as second-line antitubercular agents primarily inhibit which target?

• DNA gyrase (topoisomerase II) and topoisomerase IV
• RNA polymerase
• Enoyl-ACP reductase
• 30S ribosomal subunit

Correct Answer: DNA gyrase (topoisomerase II) and topoisomerase IV

Q19. Linezolid, used for resistant TB, has a notable adverse effect with prolonged use. What is it?

• Bone marrow suppression (e.g., thrombocytopenia)
• Nephrolithiasis
• Severe hyperglycemia
• Optic neuritis only in neonates

Correct Answer: Bone marrow suppression (e.g., thrombocytopenia)

Q20. Which newer antitubercular drug inhibits mycobacterial ATP synthase and is used for MDR/XDR-TB?

• Bedaquiline
• Isoniazid
• Ethambutol
• Pyrazinamide

Correct Answer: Bedaquiline

Q21. The mechanism of action of bedaquiline involves inhibition of which component?

• Mycobacterial ATP synthase (energy production)
• DNA-dependent RNA polymerase
• Mycolic acid synthesis via InhA
• Peptidoglycan transpeptidase

Correct Answer: Mycobacterial ATP synthase (energy production)

Q22. Pyrazinamide is particularly active against which subpopulation of Mycobacterium tuberculosis?

• Intracellular or semi-dormant organisms in acidic environments
• Fast-growing extracellular bacilli in alkaline medium
• Biofilm-associated organisms only
• Only rifampicin-resistant strains

Correct Answer: Intracellular or semi-dormant organisms in acidic environments

Q23. Which antitubercular drug commonly causes orange-red discoloration of body fluids and secretions?

• Rifampicin
• Isoniazid
• Ethambutol
• Pyrazinamide

Correct Answer: Rifampicin

Q24. For latent TB infection, which monotherapy regimen is commonly recommended historically?

• Isoniazid for 6–9 months
• Pyrazinamide for 2 months
• Ethambutol for 3 months
• Rifampicin for 12 months

Correct Answer: Isoniazid for 6–9 months

Q25. Fluoroquinolone resistance in M. tuberculosis is most commonly due to mutations in which genes?

• gyrA and gyrB (DNA gyrase genes)
• katG and inhA
• rpoB and rpoC
• embA and embB

Correct Answer: gyrA and gyrB (DNA gyrase genes)

Q26. Which monitoring is recommended before and during aminoglycoside therapy for TB?

• Baseline and periodic audiometry
• Fasting blood glucose monitoring only
• Routine fundoscopy
• No monitoring is required

Correct Answer: Baseline and periodic audiometry

Q27. Which injectable antitubercular drug is contraindicated in pregnancy due to fetal ototoxicity?

• Streptomycin
• Rifampicin
• Isoniazid
• Ethambutol

Correct Answer: Streptomycin

Q28. Isoniazid can cause pyridoxine deficiency by which mechanism?

• Enhancing urinary excretion of pyridoxine leading to deficiency
• Inhibiting pyridoxine absorption in the intestine only
• Blocking hepatic activation of vitamin D
• Increasing folate levels thereby depleting B6

Correct Answer: Enhancing urinary excretion of pyridoxine leading to deficiency

Q29. What is the typical pyridoxine supplement dose recommended with isoniazid to prevent neuropathy?

• 10–50 mg per day
• 1 g per day
• 0.1 mg per day
• 500 mg weekly

Correct Answer: 10–50 mg per day

Q30. Which first-line treatment combination includes multiple hepatotoxic agents and therefore requires regular LFT monitoring?

• 2HRZE/4HR (includes isoniazid, rifampicin, pyrazinamide)
• Ethambutol monotherapy only
• Streptomycin and ethambutol only
• Topical rifampicin gel

Correct Answer: 2HRZE/4HR (includes isoniazid, rifampicin, pyrazinamide)

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.

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