Notes on Anti-Tuberculosis Drugs, Comparative chart of first and second line drugs and MCQ for NEETPG and GPAT exams

Anti-TB drugs are categorized into:

• First-line drugs: Primary agents used for drug-sensitive TB.

• Second-line drugs: Used for drug-resistant TB (e.g., MDR-TB, XDR-TB)

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• First-Line Anti-TB Drugs

  Drug	Chemical Class	Mechanism of Action	Spectrum	Common Side Effects	Contraindications
  Isoniazid (INH)	Hydrazide derivative	Inhibits mycolic acid synthesis, disrupting cell wall formation	Active against M. tuberculosis	Hepatotoxicity, peripheral neuropathy, rash	Acute liver disease, hypersensitivity
  Rifampicin (RIF)	Rifamycin	Inhibits DNA-dependent RNA polymerase, suppressing RNA synthesis	Broad-spectrum, including M. tuberculosis	Hepatotoxicity, orange discoloration of body fluids, flu-like syndrome	Concurrent use with certain antiretrovirals, liver disease
  Pyrazinamide (PZA)	Nicotinamide analog	Converts to pyrazinoic acid, disrupting membrane transport and energy production	Active against semi-dormant TB bacilli	Hepatotoxicity, hyperuricemia, arthralgia	Severe liver disease, acute gout
  Ethambutol (EMB)	Ethylenediamine derivative	Inhibits arabinosyl transferase, impairing cell wall synthesis	Active against M. tuberculosis	Optic neuritis (visual disturbances), red-green color blindness	Optic neuritis, children under 5 years
  Streptomycin (SM)	Aminoglycoside antibiotic	Binds to 30S ribosomal subunit, inhibiting protein synthesis	Active against extracellular TB bacilli	Ototoxicity, nephrotoxicity	Pregnancy, renal impairment, auditory nerve damage

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  Second-Line Anti-TB Drugs

  Drug	Chemical Class	Mechanism of Action	Spectrum	Common Side Effects	Contraindications
  Fluoroquinolones (e.g., Levofloxacin, Moxifloxacin)	Fluoroquinolone antibiotics	Inhibit DNA gyrase and topoisomerase IV, disrupting DNA replication	Broad-spectrum, including M. tuberculosis	GI disturbances, QT prolongation, tendonitis	Tendon disorders, QT prolongation, children, pregnancy
  Amikacin, Kanamycin, Capreomycin	Aminoglycoside antibiotics	Bind to 30S ribosomal subunit, inhibiting protein synthesis	Active against M. tuberculosis	Ototoxicity, nephrotoxicity	Pregnancy, renal impairment, auditory nerve damage
  Ethionamide	Thioamide	Inhibits mycolic acid synthesis, disrupting cell wall formation	Active against M. tuberculosis	GI disturbances, hepatotoxicity, hypothyroidism	Severe liver disease, thyroid disorders
  Cycloserine	Amino acid analog	Inhibits cell wall synthesis by interfering with peptidoglycan cross-linking	Active against M. tuberculosis	CNS effects (e.g., depression, psychosis), seizures	History of seizures, psychiatric disorders
  Para-aminosalicylic acid (PAS)	Salicylic acid derivative	Inhibits folic acid synthesis, disrupting DNA synthesis	Active against M. tuberculosis	GI disturbances, hypersensitivity reactions	Severe renal or hepatic impairment
  Linezolid	Oxazolidinone antibiotic	Inhibits protein synthesis by binding to 50S ribosomal subunit	Broad-spectrum, including M. tuberculosis	Bone marrow suppression, peripheral neuropathy, lactic acidosis	Myelosuppression, uncontrolled hypertension
  Bedaquiline	Diarylquinoline	Inhibits ATP synthase, disrupting energy production	Active against M. tuberculosis	QT prolongation, hepatotoxicity	QT prolongation, hepatic impairment
  Delamanid	Nitroimidazole derivative	Inhibits mycolic acid synthesis, disrupting cell wall formation	Active against M. tuberculosis	QT prolongation, GI disturbances	QT prolongation, hepatic impairment
  Pretomanid	Nitroimidazo-oxazine derivative	Inhibits mycolic acid synthesis and induces respiratory poisoning	Active against M. tuberculosis	Hepatotoxicity, peripheral neuropathy	Severe hepatic impairment

    TB Treatment Guidelines in India (2025)

  TB Type	Treatment Regimen	Duration	Notes
  Drug-Sensitive TB (DS-TB)	Intensive Phase (IP): 2 months of daily HRZE (Isoniazid, Rifampicin, Pyrazinamide, Ethambutol) <br> Continuation Phase (CP): 4 months of daily HRE (Isoniazid, Rifampicin, Ethambutol)	6 months total	Fixed-Dose Combinations (FDCs) used as per weight bands. <br> – Directly Observed Treatment (DOT) recommended. <br> – CP may be extended up to 24 weeks in certain forms like CNS TB .
  Multidrug-Resistant TB (MDR-TB)	Shorter All-Oral Regimen (6 months): <br> – BPaLM: Bedaquiline, Pretomanid, Linezolid, Moxifloxacin <br> Longer Regimen (18–20 months): <br> – Includes drugs like Levofloxacin, Linezolid, Cycloserine, Clofazimine, etc.	6 to 20 months based on regimen	Shorter regimen for patients aged ≥14 years without extensive disease. <br> – Not recommended for pregnant women, children under 14, or patients with extrapulmonary TB . <br> – Longer regimen used when shorter regimen is contraindicated or not feasible.
  Pre-XDR and XDR-TB	Customized Regimens based on Drug Susceptibility Testing (DST): <br> – May include newer drugs like Bedaquiline, Delamanid, Linezolid, Clofazimine, etc.	18–24 months	Regimen tailored according to DST results. <br> – Close monitoring for adverse effects and treatment adherence.
  Latent TB Infection (LTBI)	6 months of daily Isoniazid (6H) <br> – 3 months of weekly Isoniazid and Rifapentine (3HP) <br> – 4 months of daily Rifampicin (4R)	3 to 6 months based on regimen	Target groups: Household contacts of TB patients, People Living with HIV (PLHIV), and other high-risk populations. <br> – Choice of regimen depends on patient eligibility, drug availability, and potential drug interactions .
  TB in Special Populations	Pregnant Women: <br> – Avoid Streptomycin due to ototoxicity risk to the fetus. <br> Children: <br> – Use pediatric formulations; avoid Ethambutol in children under 5 years. <br> PLHIV: <br> – Initiate Antiretroviral Therapy (ART) as early as possible; monitor for drug interactions.	Varies based on population and regimen	Pregnancy: Monitor liver function tests regularly. <br> – Children: Dose adjustments based on weight; monitor for side effects. <br> – PLHIV: Coordination between TB and HIV programs essential for integrated care.

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  For detailed information and updates, please refer to the official guidelines provided by the Central TB Division: National Guidelines for Management of DR-TB.

  Multiple Choice Questions (MCQs) on Antitubercular Drugs

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  1. Which first-line anti-TB drug is most commonly associated with optic neuritis?

     • A. Isoniazid

     • B. Rifampicin

     • C. Ethambutol

     • D. Pyrazinamide

     Answer: C. Ethambutol

  2. Which of the following is a second-line anti-TB drug that inhibits ATP synthase?

     • A. Linezolid

     • B. Bedaquiline

     • C. Cycloserine

     • D. Ethionamide

     Answer: B. Bedaquiline

  3. The BPaLM regimen includes all of the following drugs EXCEPT:

     • A. Bedaquiline

     • B. Pretomanid

     • C. Linezolid

     • D. Ethambutol

     Answer: D. Ethambutol

  4. Which anti-TB drug is known for causing peripheral neuropathy, especially in patients with vitamin B6 deficiency?

     • A. Rifampicin

     • B. Isoniazid

     • C. Pyrazinamide

     • D. Streptomycin

     Answer: B. Isoniazid

  5. Which of the following drugs is contraindicated in pregnancy due to its ototoxic effects on the fetus?

     • A. Ethambutol

     • B. Streptomycin

     • C. Isoniazid

     • D. Rifampicin

     Answer: B. Streptomycin