isoniazid + rifampin + ethambutol + streptomycin

This drug is a fixed-dose combination of four first-line antitubercular agents—isoniazid, rifampin, ethambutol, and streptomycin—used primarily in the initial intensive phase of tuberculosis (TB) treatment. Each component has a distinct mechanism of action against Mycobacterium tuberculosis: - Isoniazid inhibits mycolic acid synthesis, disrupting cell wall formation. - Rifampin inhibits DNA-dependent RNA polymerase, blocking RNA synthesis. - Ethambutol impairs arabinosyl transferases involved in cell wall biosynthesis. - Streptomycin binds to the 30S ribosomal subunit, inhibiting protein synthesis. The combination is used to prevent resistance development and ensure effective bactericidal activity. It is indicated for active TB disease (including pulmonary and extrapulmonary forms), especially when drug susceptibility patterns are unknown or resistance risk is high. The regimen may be adjusted based on susceptibility testing results[1][2][6].