H mono resistant tb full details for md exam answer 15 marks from this pdf only with replacement sequence
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I now have all the content needed from both PDFs. Let me compile the comprehensive 15-mark MD exam answer:
Isoniazid (H) Mono/Poly Drug-Resistant TB — Full Details (15 Marks)
Based on PMDT Guidelines 2021 & March 2025 (NTEP)
1. Definition
H mono-resistant TB: TB caused by M. tuberculosis resistant to Isoniazid (H) only, with susceptibility to Rifampicin confirmed.
H poly-resistant TB: Resistance to H and one or more other first-line drugs (but NOT Rifampicin), i.e., does not meet the criteria for MDR-TB.
Both are managed under the same H mono/poly DR-TB regimen.
2. Diagnosis & Pre-requisite
- NAAT (CBNAAT/Truenat) must confirm Rifampicin resistance NOT detected
- FL-LPA confirms H resistance (katG / inhA mutation)
- Empirical treatment of H mono/poly DR-TB is NOT advised — Rifampicin susceptibility must be excluded first
- Once FL-LPA shows H resistance → LPA deposit sent for SL-LPA and LC-DST to: Mfx, Z, Lzd, Cfz*
- Patient need not be sent to DDR-TBC unless medically necessary; treatment initiated at peripheral health facility level itself while awaiting SL-LPA/LC-DST results
- Results uploaded by microbiologist on Nikshay on the same day
3. Pre-Treatment Evaluation (PTE)
| Investigation | Requirement |
|---|---|
| History & physical examination | Mandatory |
| Height / Weight | Mandatory |
| Random Blood Sugar (RBS) | Mandatory |
| Chest X-ray | Mandatory |
| HIV test | Mandatory |
| Additional investigations | Only if clinically indicated |
- PTE valid for 1 month from date of test; can be used for re-initiation
- aDSM (active Drug Safety Management) initiation form completed for all DR-TB patients
4. Regimen
Regimen: Lfx – R – Z – E (6 or 9 months)
(Levofloxacin + Rifampicin + Pyrazinamide + Ethambutol)
In exceptional situations where loose R, E or Z is unavailable, 4-FDC (HREZ) + Lfx loose tablets may be used as an alternative rather than delaying treatment.
5. Dosage (Weight-Band Based)
| Drug | 16–29 kg | 30–45 kg | 46–70 kg | >70 kg |
|---|---|---|---|---|
| Rifampicin (R) | 300 mg | 450 mg | 600 mg | 750 mg |
| Ethambutol (E) | 400 mg | 800 mg | 1200 mg | 1600 mg |
| Pyrazinamide (Z) | 750 mg | 1250 mg | 1750 mg | 2000 mg |
| Levofloxacin (Lfx) | 250 mg | 750 mg | 1000 mg | 1000 mg |
6. Inclusion & Exclusion Criteria
Inclusion:
- Rifampicin resistance NOT detected (by NAAT) + H resistance detected (by FL-LPA)
- Age ≥ 5 years (weight ≥ 16 kg)
- New or previously treated (not prior treatment failure with FQ-containing regimen)
Exclusion:
- R resistance detected/inferred (switch to MDR-TB regimen)
- FQ resistance detected
- Severe hepatic dysfunction
- Prior failure on FQ-containing regimen (without documented susceptibility)
- Children < 5 years (manage differently)
7. Treatment Duration & Extension
| Condition | Duration |
|---|---|
| Standard | 6 months |
| Extension indications | 9 months (extended directly — no monthly extensions) |
Indications for direct extension to 9 months:
- Extensive pulmonary disease (bilateral cavitary/extensive parenchymal damage)
- Uncontrolled comorbidity
- Extra-pulmonary TB
- Smear positive at end of Month 4
- Regimen modification (use of replacement drugs)
Important: There are NO monthly extensions in this regimen — extension is from 6 months directly to 9 months.
In extensive pulmonary TB, prolongation up to 12 months may be considered on an individual basis.
Treatment Failure: If smear/culture remains positive at end of Month 5 or later, declare as 'Treatment Failed' → re-evaluate as non-responder.
8. Replacement Sequence (KEY TABLE — PMDT 2021 & 2025)
As per PMDT 2021 Guidelines:
| Situation | Replacement Sequence |
|---|---|
| If Lfx cannot be used | Replace with Mfx(h) if SL-LPA pattern suggests susceptibility. Do LC-DST for Mfx(h), Z, Lzd & Cfz* |
| If Mfx(h) or Z cannot be used | Replace with Lzd. If Lzd also cannot be given → replace with Cfz + Cs* |
| If BOTH Mfx(h) and Z cannot be used | Add 2 drugs from: Lzd, Cfz, Cs* — in order of preference based on resistance, tolerability & availability |
| If R resistance develops | Switch to appropriate shorter or longer oral MDR/RR-TB regimen |
Cfz — DST whenever available. In the first three situations above, treat for a total duration of 9 months. The use of new drugs (Bdq, Pa) is not yet recommended in H mono/poly DR-TB treatment.
As per PMDT March 2025 Guidelines (Updated):
| Situation | Replacement Sequence |
|---|---|
| 1. If Lfx or Z cannot be used | Replace with Lzd. If Lzd also cannot be given → replace with Cfz + Cs* |
| 2. If BOTH Lfx and Z cannot be used | Add 2 drugs from: Lzd, Cfz, Cs* — in order of preference based on resistance, tolerability & availability |
| 3. If R resistance | Switch to appropriate shorter or longer oral regimen |
Key Update (2025): Mfx(h) as first replacement for Lfx was in 2021; in 2025 the table directly uses Lzd as first replacement for Lfx or Z, and patients not responding with R/FQ/Z resistance are considered "probable MDR-TB" → evaluated for BPaLM, then shorter 9-month MDR regimen, then longer oral M/XDR-TB regimen.
Note on regimen change: If any change is required in the H mono/poly DR-TB regimen during the initial 4 months (due to resistance, intolerability, unavailability, contraindication), re-initiation or re-registration is NOT required — patient continues with the same registration date with modifications.
9. Follow-Up Monitoring
| Parameter | Schedule |
|---|---|
| Clinical + Weight | Monthly till end of treatment |
| Sputum Smear Microscopy | Monthly from Month 3 onwards |
| Culture | End of Month 3; End of treatment (Month 6 and/or 9) |
| DST (NAAT, FL-LPA, SL-LPA, LC-DST) | If smear/culture positive at Month 3 or end of treatment |
| Colour vision test | Once in 2 months (in children, due to Ethambutol) |
| CBC/platelets | As clinically indicated (mandatory if Lzd used — bone marrow suppression) |
| LFT / TSH | As clinically indicated |
| CXR | As clinically indicated + at end of treatment |
| ECG | If Mfx(h) or Cfz used: daily for initial 3 days if baseline QTcF ≥450 ms; then as indicated |
| Electrolytes (K, Mg, Ca) | As clinically indicated |
Long-term follow-up: 6-monthly cultures among symptomatic patients till 2 years post-treatment (months 6, 12, 18, 24 post-treatment completion).
Final treatment outcome is declared based on culture results (not smear alone).
10. Adverse Drug Reactions
| ADR | Causative Drug(s) |
|---|---|
| Hepatitis | R, Z |
| QT prolongation | FQ, Cfz |
| Gastrointestinal symptoms | Z, E, Cfz, FQs |
| Peripheral neuropathy | FQ, E |
| Optic neuritis | E, Lzd, Cfz |
| Seizures, psychotic symptoms | FQ |
| Tendonitis/tendon rupture | FQ |
| Arthralgia | Z, FQ |
| Bone marrow suppression | Lzd |
| Rash/anaphylaxis | Any drug |
11. Special Populations
Children
- Management same as adults; child-friendly formulations used
- Colour vision monitoring every 2 months (Ethambutol)
- Children < 5 years managed differently
Pregnancy & Lactation
- H mono/poly DR-TB regimen may be started or continued in pregnant women
- Rifampicin interacts with oral contraceptives → recommend higher dose estrogen OCP (50 µg) or barrier methods / IUD / depot-medroxyprogesterone
PLHIV
- H mono/poly DR-TB regimen recommended in HIV-reactive TB patients
- ART must be started within 8 weeks of TB treatment initiation regardless of CD4 count
Extra-pulmonary TB
- Close consultation with appropriate specialists (ID physicians, neurologists)
- CNS, skeletal, miliary TB: treatment may be given up to 1 year
12. Evidence Base
- Addition of fluoroquinolone (Lfx) to (H)REZ regimen:
- Higher treatment success: aOR 2.8 (95% CI: 1.1–7.3)
- Reduced deaths: aOR 0.4 (95% CI: 0.2–1.1)
- Reduced acquisition of additional resistance/MDR-TB progression: aOR 0.10 (95% CI: 0.01–1.2)
- Duration: 6(H)REZ had higher success than >6(H)REZ
- Median FQ duration: 6.1 months (IQR 3.5–8.4); REZ: 9 months
Summary Mnemonic
"H mono: Lfx-R-Z-E for 6(9) months, peripheral facility, culture-based outcome, replace in sequence (Lzd → Cfz+Cs), never empirical, no new drugs"
Sources: PMDT Guidelines 2021 (Slides 45–65) & PMDT Guidelines March 2025 (Slides 7, 26–27) — National TB Elimination Programme (NTEP), India
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