วันอังคารที่ 3 มีนาคม พ.ศ. 2569

Pulmonary Tuberculosis: Treatment of Drug-Susceptible (Adult, HIV-negative)

Pulmonary Tuberculosis: Treatment of Drug-Susceptible (Adult, HIV-negative)

1) Goals of TB treatment (Core principles)

เป้าหมายหลัก 4 ข้อ:

1.       Eradication ของ M. tuberculosis

2.       ลดการแพร่เชื้อ (transmission control)

3.       ป้องกัน recurrence

4.       ป้องกัน drug resistance

แนวคิดสำคัญ:

Patient-centered care + public health integration (DOT, reporting, adherence)

2) Pre-treatment evaluation (ต้องทำก่อนเริ่มยาเสมอ)

2.1 Confirm diagnosis & baseline workup

  • Sputum AFB smear + culture + NAAT
  • Drug susceptibility testing (DST) (if available)
  • CXR baseline
  • HIV testing (mandatory in all TB patients)

2.2 Baseline labs (standard clinical practice)

  • CBC
  • LFT (AST/ALT, bilirubin, ALP)
  • Creatinine
  • Uric acid (if PZA)
  • Visual acuity & color vision (if EMB)
  • Pregnancy test (if applicable)

3) First-line antituberculous drugs (RIPE regimen)

Drug

Key role

Major toxicity

Isoniazid (INH)

Core bactericidal

Hepatitis, neuropathy

Rifampin (RIF)

Sterilizing, prevents relapse

Hepatitis, DDI

Pyrazinamide (PZA)

Sterilizing (early phase)

Hepatotoxicity, hyperuricemia

Ethambutol (EMB)

Resistance prevention

Optic neuritis

Clinical mnemonic: IRZE therapy

4) Standard Treatment Regimen (Traditional ≥6 months) — Standard of care

4.1 Treatment phases

1) Intensive phase (2 months)

INH + RIF + PZA + EMB (HRZE)
Duration: 8 weeks

2) Continuation phase (≥4 months)

INH + RIF (HR)
Total duration: ≥6 months

International notation:

2HRZE / 4HR

5) Regimen selection (Practical clinical approach)

Preferred (most patients):

  • Traditional 6-month regimen = standard of care

Alternative (selected patients only):

  • 4-month rifapentine-moxifloxacin regimen

6) Shortened 4-month regimen (Rifapentine + Moxifloxacin)

6.1 Regimen structure

Intensive phase (8 weeks)

  • Rifapentine + INH + PZA + Moxifloxacin (daily)

Continuation phase (9 weeks)

  • Rifapentine + INH + Moxifloxacin (daily)

Total = 4 months (119 doses)

6.2 Eligible patients (very important selection criteria)

ใช้ได้เฉพาะ:

  • Age ≥12 years
  • Weight ≥40 kg
  • Drug-susceptible pulmonary TB
  • Nonpregnant
  • No extrapulmonary TB
  • Rapid DST available

6.3 Contraindications (ห้ามใช้)

  • Suspected drug-resistant TB
  • Pregnancy / lactation
  • Significant cardiac disease / prolonged QT
  • Baseline QTc >450 ms (expert-dependent)
  • Severe liver disease
  • Renal failure
  • Drug interactions (rifamycin)
  • Extrapulmonary TB
  • Poor adherence risk

⚠️ Not recommended in:

  • Cavitary disease (relative caution)
  • Smear-positive high burden disease (some data less robust)

7) Monitoring during treatment (High-yield clinical workflow)

7.1 Clinical response

Expected:

  • Symptom improvement: 2–3 weeks
  • Cough ↓, fever ↓, weight ↑
    Radiology may lag behind clinical response

Lack of improvement → evaluate:

  • Drug resistance
  • Nonadherence
  • Malabsorption
  • Wrong diagnosis

7.2 Sputum monitoring (critical)

Recommended:

  • Monthly sputum AFB smear + culture
    until 2 consecutive culture negative

Key interpretation:

  • Positive culture at 2 months → DST + reassess
  • Positive culture >3 months → investigate failure
  • Positive culture >4 months → treatment failure

7.3 Role of imaging follow-up

  • Routine CXR not required if clinical improvement
  • Consider CXR:
    • Slow response
    • End of therapy baseline
    • Complications

8) Duration adjustment (Advanced exam + real clinical use)

8.1 Standard 6 months sufficient if:

  • Culture negative at 2 months
  • No cavitary disease

8.2 Extend to 9 months if:

  • Cavitary disease + culture positive at 2 months
  • Delayed culture conversion
  • Extensive disease
  • Underweight (>10% below IBW)
  • Diabetes
  • Smoking
  • Immunocompromised

9) Special scenario: Culture-negative pulmonary TB

Regimen:

  • 2 months HRZE
  • Followed by 2 months HR
    Total = 4 months

(If clinical + radiologic improvement and no alternative diagnosis)

10) Treatment adherence (Critical for resistance prevention)

Directly Observed Therapy (DOT) — Preferred

Benefits:

  • Ensures adherence
  • Detects toxicity early
  • Reduces relapse & resistance
  • Public health control

Daily therapy > intermittent therapy
(Intermittent dosing associated with worse outcomes)

11) Interrupted treatment (Practical decision)

Key factors:

  • When interruption occurred
  • Duration of interruption
  • Disease burden

Principle:

Interruptions in intensive phase are most dangerous
(Highest bacterial load + resistance risk)

May need:

  • Extend therapy
  • Restart regimen (if long interruption early)

12) Adverse effect monitoring (Clinical safety essentials)

12.1 Hepatotoxicity (most important)

Common culprits:

  • INH
  • RIF
  • PZA (highest risk)

When to stop hepatotoxic drugs:

  • AST/ALT >5× ULN (asymptomatic)
  • AST/ALT >3× ULN + symptoms
  • Bilirubin ≥3 mg/dL

Management:

  • Stop hepatotoxic drugs
  • Rule out other causes (viral hepatitis, alcohol)
  • Reintroduce drugs sequentially after LFT improves

12.2 Reintroduction strategy (classic approach)

  • Restart RIF first (if non-cholestatic)
  • Then INH after 1–2 weeks
  • Add PZA last (if tolerated)
  • If severe hepatotoxicity → avoid PZA → extend to 9 months

13) Drug intolerance: Alternative regimens (High-yield)

Drug intolerance

Alternative

INH intolerance

RIF + PZA + EMB + FQ (≈6 mo)

RIF intolerance

INH + EMB ± PZA (12–18 mo)

PZA intolerance

INH + RIF (9 mo)

All hepatotoxic drugs

EMB + FQ + second-line drugs (18–24 mo)

(Expert consultation recommended)

14) Special clinical populations

14.1 Renal failure

  • Adjust EMB, PZA dosing
  • Give after hemodialysis
  • Prefer interval adjustment over dose reduction
  • Avoid 4-month regimen

14.2 Liver disease

  • High risk hepatotoxicity
  • Close LFT monitoring (≥monthly)
  • Consider liver-sparing regimen
  • Expert consult strongly advised

14.3 Malnutrition

  • Increased mortality & recurrence risk
  • Nutritional supplementation recommended
  • Weight gain improves outcomes

15) Pyridoxine (Vitamin B6) supplementation

Give 25–50 mg/day with INH in:

  • Diabetes
  • HIV
  • Alcoholism
  • Malnutrition
  • CKD
  • Pregnancy
  • Elderly

Prevents: peripheral neuropathy

16) Treatment failure & recurrence

Definitions

  • Failure: positive culture after 4 months therapy
  • Recurrence: TB after apparent cure (usually 6–12 months)

Risk factors:

  • Cavitary disease
  • High bacillary load
  • Drug resistance
  • Poor adherence
  • Malabsorption
  • Malnutrition

Management:

  • Repeat DST (first + second line)
  • Review adherence
  • Drug level monitoring (if suspected malabsorption)
  • Expert TB consultation

17) Role of steroids in TB

Indicated:

  • TB meningitis
  • TB pericarditis (risk constrictive)
    Not routinely indicated:
  • Uncomplicated pulmonary TB
    (uncertain benefit except specific complications)

18) Extrapulmonary TB (quick clinical note)

  • Standard duration ≥6 months
  • CNS TB: 12 months
  • Bone/joint: 6–9 months
    ⚠️ 4-month regimen NOT recommended

19) Prognosis (Real-world data)

  • Global treatment success: ~85%
  • Mortality: ~15% (global)
  • Recurrence (drug-susceptible TB): ~5%
  • US failure/recurrence: 2.5–5%

Prognosis depends on:

  • Early treatment initiation
  • Adherence
  • Disease severity
  • Comorbidities
  • Drug resistance

20) Ultra–high yield clinical checklist (สำหรับแพทย์เวชปฏิบัติ/ER)

Start standard TB regimen when:

  • Microbiologic confirmation OR
  • High clinical suspicion + typical imaging + risk factors

Order set (practical):

  • IRZE regimen (weight-based)
  • Pyridoxine
  • Baseline CBC, LFT, Cr
  • HIV test
  • Monthly sputum AFB + culture
  • DOT coordination
  • Public health notification
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