Antitubercular antibiotics like Rifampicin, Rifabutin, Cycloserine, Streptomycin and Capreomycin form the backbone of tuberculosis therapy, including management of multidrug-resistant TB. This introduction reviews mechanisms of action (rifamycins inhibit bacterial RNA polymerase; cycloserine blocks D‑alanine enzymes; aminoglycosides and capreomycin disrupt protein synthesis), pharmacokinetics, major adverse effects (hepatotoxicity, neurotoxicity, ototoxicity, nephrotoxicity), important drug interactions (CYP induction by rifamycins), monitoring strategies and resistance mechanisms. Designed for B.Pharm students, the material emphasizes clinical relevance, dosing considerations, toxicity prevention and stewardship. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which is the primary mechanism of action of Rifampicin?
- Inhibition of DNA-dependent RNA polymerase
- Inhibition of DNA gyrase
- Inhibition of 30S ribosomal subunit
- Inhibition of cell wall synthesis by blocking peptidoglycan cross-linking
Correct Answer: Inhibition of DNA-dependent RNA polymerase
Q2. Which of the following is a characteristic adverse effect of Rifampicin?
- Orange-red discoloration of body fluids and hepatotoxicity
- Severe peripheral neuropathy requiring pyridoxine
- Ototoxicity with irreversible hearing loss
- Bone marrow aplasia
Correct Answer: Orange-red discoloration of body fluids and hepatotoxicity
Q3. Why is Rifabutin sometimes preferred over Rifampicin in HIV-TB co-infected patients on protease inhibitors?
- Rifabutin is a stronger CYP450 inducer than Rifampicin
- Rifabutin has less potent CYP450 induction and fewer interactions with protease inhibitors
- Rifabutin causes less hepatotoxicity but more nephrotoxicity
- Rifabutin is only available intravenously which improves adherence
Correct Answer: Rifabutin has less potent CYP450 induction and fewer interactions with protease inhibitors
Q4. What is the primary mechanism of action of Cycloserine?
- Inhibition of DNA-dependent RNA polymerase
- Inhibition of D-alanine racemase and D-alanine–D-alanine ligase involved in cell wall synthesis
- Inhibition of 30S ribosomal subunit causing misreading of mRNA
- Inhibition of mycolic acid synthesis
Correct Answer: Inhibition of D-alanine racemase and D-alanine–D-alanine ligase involved in cell wall synthesis
Q5. Which central nervous system adverse effects are classically associated with Cycloserine?
- Seizures, psychosis and depression that may be prevented with pyridoxine
- Auditory and vestibular toxicity leading to dizziness and hearing loss
- Hepatic enzyme elevation with jaundice
- Peripheral neuropathy independent of pyridoxine status
Correct Answer: Seizures, psychosis and depression that may be prevented with pyridoxine
Q6. What is the mechanism of action of Streptomycin against Mycobacterium tuberculosis?
- Inhibition of peptidoglycan polymerization
- Irreversible binding to the 30S ribosomal subunit causing misreading and bactericidal effect
- Inhibition of RNA polymerase like rifamycins
- Blocking mycolic acid synthesis in the cell wall
Correct Answer: Irreversible binding to the 30S ribosomal subunit causing misreading and bactericidal effect
Q7. The most clinically significant toxicities of Streptomycin include:
- Ototoxicity and nephrotoxicity
- Severe hepatotoxicity and thrombocytopenia
- Bone marrow suppression and hemolysis
- Pancytopenia and peripheral neuropathy
Correct Answer: Ototoxicity and nephrotoxicity
Q8. Capreomycin’s antibacterial action is best described as:
- Inhibition of DNA replication by targeting DNA gyrase
- Disruption of mycolic acid synthesis in the cell wall
- Inhibition of protein synthesis by binding the 70S ribosome and interfering with translocation
- Inhibition of folate synthesis
Correct Answer: Inhibition of protein synthesis by binding the 70S ribosome and interfering with translocation
Q9. In current TB practice, Capreomycin is primarily used for which indication?
- First-line treatment of drug-sensitive pulmonary TB
- Prophylaxis for latent TB infection
- Management of multidrug-resistant TB as a parenteral second-line agent
- Routine use for TB meningitis only
Correct Answer: Management of multidrug-resistant TB as a parenteral second-line agent
Q10. A major clinical consequence of Rifampicin’s strong induction of hepatic CYP450 enzymes is:
- Increased plasma levels of warfarin and oral contraceptives
- Reduced plasma concentrations and efficacy of co-administered drugs like warfarin and oral contraceptives
- No significant drug interactions with antiretroviral drugs
- Specific inhibition of CYP2D6 only
Correct Answer: Reduced plasma concentrations and efficacy of co-administered drugs like warfarin and oral contraceptives
Q11. Resistance to Rifampicin in M. tuberculosis most commonly arises from mutations in which gene?
- katG gene encoding catalase-peroxidase
- rpoB gene encoding the beta subunit of RNA polymerase
- inhA promoter region involved in mycolic acid synthesis
- rpsL gene encoding ribosomal protein S12
Correct Answer: rpoB gene encoding the beta subunit of RNA polymerase
Q12. Which of the following antitubercular drugs is generally considered bacteriostatic rather than bactericidal against M. tuberculosis?
- Rifampicin
- Cycloserine
- Streptomycin
- Capreomycin
Correct Answer: Cycloserine
Q13. Therapeutic drug monitoring (peak and trough levels) is most important for which drug among these?
- Rifampicin
- Cycloserine
- Streptomycin
- Rifabutin
Correct Answer: Streptomycin
Q14. Which antitubercular agent significantly reduces the efficacy of hormonal contraceptives due to induction of hepatic enzymes?
- Cycloserine
- Capreomycin
- Rifampicin
- Streptomycin
Correct Answer: Rifampicin
Q15. A notable adverse effect associated with Rifabutin, especially when used with certain antiretrovirals, is:
- Severe peripheral neuropathy
- Uveitis and neutropenia
- Irreversible ototoxicity
- Pseudomembranous colitis
Correct Answer: Uveitis and neutropenia
Q16. Cycloserine is relatively contraindicated in patients with which pre-existing condition?
- History of seizure disorder
- Mild hepatic enzyme elevation only
- Controlled hypertension
- Asymptomatic bacteriuria
Correct Answer: History of seizure disorder
Q17. Common mechanisms of Streptomycin resistance in M. tuberculosis include mutations in which target?
- Mutations in rpoB leading to altered RNA polymerase
- Mutations in rpsL (ribosomal S12 protein) or rrs (16S rRNA)
- Overexpression of efflux pumps specific to rifamycins
- Alterations in mycolic acid synthesis enzymes
Correct Answer: Mutations in rpsL (ribosomal S12 protein) or rrs (16S rRNA)
Q18. Which antitubercular drug commonly requires concomitant pyridoxine (vitamin B6) to reduce neurotoxic effects?
- Rifampicin
- Cycloserine
- Capreomycin
- Rifabutin
Correct Answer: Cycloserine
Q19. The principal toxicities to monitor during Capreomycin therapy are:
- Hepatotoxicity and skin hyperpigmentation
- Nephrotoxicity and ototoxicity similar to aminoglycosides
- Severe agranulocytosis only
- Cardiac QT prolongation exclusively
Correct Answer: Nephrotoxicity and ototoxicity similar to aminoglycosides
Q20. Which of the following antitubercular agents is commonly administered parenterally (intramuscular or intravenous)?
- Rifampicin
- Cycloserine
- Streptomycin
- Rifabutin
Correct Answer: Streptomycin
Q21. Compared to Rifampicin, Rifabutin has which pharmacokinetic advantage relevant to long-term prophylaxis against MAC in HIV patients?
- Much shorter half-life requiring multiple daily doses
- Longer half-life allowing less frequent dosing and fewer drug interactions
- No hepatic metabolism and no need for dose adjustment
- Complete renal excretion avoiding hepatic toxicity
Correct Answer: Longer half-life allowing less frequent dosing and fewer drug interactions
Q22. Cycloserine inhibits bacterial cell wall synthesis by interfering with which biochemical step?
- Inhibition of mycolic acid condensation
- Blocking formation of D-alanine–D-alanine dipeptide through inhibition of D-alanine enzymes
- Inhibition of transpeptidase (penicillin-binding proteins)
- Prevention of lipid II flipping across the membrane
Correct Answer: Blocking formation of D-alanine–D-alanine dipeptide through inhibition of D-alanine enzymes
Q23. Orange discoloration of tears, urine, and saliva is most likely caused by which antitubercular drug?
- Streptomycin
- Cycloserine
- Rifampicin
- Capreomycin
Correct Answer: Rifampicin
Q24. Co-administration of Rifampicin with protease inhibitors used in HIV therapy typically results in:
- Increased protease inhibitor levels and enhanced efficacy
- No interaction due to different metabolic pathways
- Marked reduction in protease inhibitor plasma concentrations risking virologic failure
- Prolongation of protease inhibitor half-life without clinical effect
Correct Answer: Marked reduction in protease inhibitor plasma concentrations risking virologic failure
Q25. Before and during Rifampicin therapy, which laboratory monitoring is recommended routinely?
- Baseline and periodic liver function tests (LFTs)
- Daily complete blood counts only
- Routine therapeutic drug monitoring of Rifampicin serum levels in all patients
- No monitoring is required for otherwise healthy adults
Correct Answer: Baseline and periodic liver function tests (LFTs)
Q26. Historically, which injectable antibiotic was one of the first effective treatments for tuberculosis and remains an option in certain regimens?
- Rifabutin
- Streptomycin
- Cycloserine
- Rifampicin
Correct Answer: Streptomycin
Q27. Resistance to Cycloserine most commonly arises through mutations affecting which target?
- Mutations in RNA polymerase beta subunit (rpoB)
- Mutations in D-alanine racemase or D-alanine–D-alanine ligase
- Methylation of 16S rRNA preventing aminoglycoside binding
- Increased cell wall permeability to efflux pumps
Correct Answer: Mutations in D-alanine racemase or D-alanine–D-alanine ligase
Q28. Which antitubercular drug is contraindicated in pregnancy because of risk of congenital deafness?
- Rifampicin
- Streptomycin
- Cycloserine
- Rifabutin
Correct Answer: Streptomycin
Q29. Vestibular toxicity presenting with imbalance and oscillopsia is most characteristic of which drug?
- Rifampicin
- Capreomycin
- Cycloserine
- Streptomycin
Correct Answer: Streptomycin
Q30. Dose adjustment and careful monitoring are especially required for which drug in patients with renal impairment?
- Rifampicin (no adjustment needed normally)
- Cycloserine (primarily hepatic clearance)
- Streptomycin (renal excretion with accumulation and toxicity risk)
- Rifabutin (excreted unchanged in urine)
Correct Answer: Streptomycin (renal excretion with accumulation and toxicity risk)
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