Antituberculosis agents: isoniazid, rifampin, streptomycin, ethambutol

Effective antituberculosis drugs have radically improved the prognosis of the patient with active tuberculosis. Surgical therapy is rarely needed, and sanatoria have largely vanished. Initially, triple-drug therapy is indicated in cavitary pulmonary disease and severe renal disease and it is generally used in miliary tuberculosis and meningitis. Use of one of the three drugs may be discontinued after there is evidence that the bacillary population has been decreased. Two-drug therapy is indicated for other active disease. Isoniazid alone is adequate for prophylaxis. The major cause of therapeutic failure is failure of the patient to take the antituberculosis medication regularly. The second major cause of treatment failure is resistance of tubercle bacilli to the antimicrobials used. When treatment failure is apparent, careful reassessment by experienced physicians is indicated. A single drug should never be added to a failing regimen.