What is the standard regimen for antitubercular (antituberculosis) therapy?

Standard Regimen for Antitubercular Therapy

The standard regimen for drug-sensitive tuberculosis consists of an initial 2-month intensive phase with isoniazid, rifampicin, pyrazinamide, and ethambutol (HRZE), followed by a 4-month continuation phase with isoniazid and rifampicin (HR), administered daily for a total of 6 months. 1, 2

Initial Phase (First 2 Months)

• Four-drug regimen:
  • Isoniazid (H): 5 mg/kg (up to 300 mg) daily 3
  • Rifampicin (R): 600 mg daily for adults 2
  • Pyrazinamide (Z): 15-30 mg/kg daily 2, 4
  • Ethambutol (E): 15 mg/kg daily 2, 5

Continuation Phase (Next 4 Months)

• Two-drug regimen:
  • Isoniazid (H): 5 mg/kg (up to 300 mg) daily 3
  • Rifampicin (R): 600 mg daily for adults 2

Administration

• Daily dosing is strongly recommended throughout the treatment course 1
• Fixed-dose combinations (FDCs) may provide a more convenient form of drug administration 1
• Directly Observed Therapy (DOT) is recommended to ensure adherence and prevent development of drug resistance 2, 3

Special Considerations

Extended Treatment Duration

The continuation phase should be extended to 7 months (total 9 months) in the following scenarios:

• Patients with cavitary pulmonary TB and positive sputum cultures after 2 months of treatment
• Patients whose initial phase did not include pyrazinamide
• Patients receiving isoniazid and rifapentine once weekly with positive cultures after 2 months 2

Extrapulmonary TB

• Most forms can be treated with the same 6-month regimen as pulmonary TB
• Exceptions requiring longer treatment:
  • TB meningitis/CNS TB: 12 months
  • TB of prosthetic joints: 12-18 months 2

Adjunctive Therapy

• Pyridoxine (vitamin B6, 25-50 mg/day) should be given with isoniazid to patients at risk of neuropathy (pregnant women, breastfeeding women, HIV patients, diabetics, alcoholics, malnourished individuals, patients with chronic renal failure, and older adults) 2
• Corticosteroids are recommended for TB meningitis, TB pericarditis, renal TB, and spinal TB with cord compression 1

Monitoring

• Monthly clinical evaluations to assess treatment response, adherence, and adverse effects
• Sputum cultures at 2 months to assess response and determine if continuation phase needs extension
• Liver function tests in patients with pre-existing liver disease or symptoms of hepatotoxicity 2

Drug Resistance Considerations

• Ethambutol can be discontinued once susceptibility to isoniazid and rifampicin is confirmed 2
• For suspected or confirmed drug-resistant TB, consultation with a TB expert is necessary 6
• Cases with rifampicin mono-resistance and MDR-TB should be treated in specialized centers with experience 1

Common Pitfalls to Avoid

1. Inadequate initial regimen: Always start with all four drugs (HRZE) in the intensive phase until drug susceptibility is confirmed
2. Poor adherence monitoring: Implement DOT or other adherence support strategies to prevent treatment failure and drug resistance
3. Insufficient treatment duration: Don't shorten treatment below 6 months for drug-sensitive TB as this increases relapse rates 7
4. Overlooking comorbidities: Patients with diabetes may have poorer response to standard treatment and may require closer monitoring 8
5. Missing drug interactions: Rifampicin has numerous drug interactions that must be carefully managed

By following this standardized approach to TB treatment, the goals of curing individual patients and minimizing transmission of Mycobacterium tuberculosis can be achieved with high success rates.