- The first-line treatment for drug-sensitive tuberculosis consists of a four-drug regimen: rifampicin, isoniazid, pyrazinamide, and ethambutol.
- This combination is recommended because it provides effective bactericidal and sterilizing activity, preventing the development of drug resistance.
- Rifampicin and isoniazid are the most potent drugs, while pyrazinamide acts in acidic environments like macrophages, and ethambutol serves as a safeguard against resistance during the initial intensive phase.
- This regimen is administered for 2 months (intensive phase) followed by 4 months of isoniazid and rifampicin (continuation phase), ensuring cure in most cases of drug-sensitive tuberculosis.

Reference: Davidson’s Principles and Practice of Medicine, 23rd Edition, Chapter: Tuberculosis, Page 765.