Treatment of Newly Diagnosed Drug-Sensitive Tuberculosis in Adults

Initial Phase (First 2 Months)

The American Thoracic Society, Centers for Disease Control and Prevention, and Infectious Diseases Society of America guidelines recommend a 6-month regimen consisting of isoniazid, rifampin, pyrazinamide, and ethambutol (HRZE) for 2 months, followed by isoniazid and rifampin (HR) for 4 months for a typical adult with newly diagnosed drug-sensitive pulmonary tuberculosis 1, 2
The intensive phase must include four drugs to maximize bacterial killing and prevent resistance development, according to the American Family Physician 1, 2
The fourth drug (ethambutol) can only be omitted if drug susceptibility testing confirms full sensitivity to isoniazid and rifampin, or in previously untreated patients at very low risk for drug resistance (HIV-negative, not contacts of drug-resistant cases) 3, 5, 4

The American Family Physician guidelines recommend continuing with isoniazid and rifampin (HR) for 4 months after completing the 2-month intensive phase 1, 2, 5

Multiple evidence-based dosing schedules are acceptable, including daily throughout, daily for 2 weeks then twice weekly for 6 weeks, and three times weekly throughout, according to the American Family Physician 1, 3, 2

The American Thoracic Society, Centers for Disease Control and Prevention, and Infectious Diseases Society of America guidelines emphasize the importance of performing drug susceptibility testing on all initial isolates before or immediately after starting treatment 6
Modify the regimen once susceptibility results become available, and if susceptibility results are pending after 2 months, continue all four drugs (including pyrazinamide and ethambutol) until full susceptibility is confirmed 6, 3, 5

The American Family Physician guidelines recommend using the same 6-month regimen for drug-sensitive TB in HIV-positive patients, and avoiding highly intermittent regimens (once or twice weekly) in patients with CD4+ counts <100 cells/mm³ due to increased risk of rifampin resistance 1, 2, 6
Most forms of extrapulmonary TB can be treated with the same 6-month regimen used for pulmonary disease, according to the Thorax journal 3, 5, 6

If isoniazid resistance is confirmed but rifampin susceptibility is maintained, use rifampin, ethambutol, pyrazinamide, and a fluoroquinolone (levofloxacin or moxifloxacin) for 6 months, according to the Praxis Medical Insights: Practical Summaries of Clinical Guidelines 6

Pyridoxine (vitamin B6) 25-50 mg daily should be added to prevent isoniazid-induced peripheral neuropathy in patients with diabetes, HIV infection, malnutrition, alcohol use disorder, chronic renal failure, or pregnancy, according to the Thorax journal and Praxis Medical Insights: Practical Summaries of Clinical Guidelines 3, 5, 7