Present status of chemotherapy for tuberculosis.

For the treatment of smear-positive pulmonary tuberculosis, short-course chemotherapy of 6 months' duration (with the four-drug combination of isoniazid, rifampin, pyrazinamide, and either ethambutol or streptomycin given daily for a 2-month initial intensive phase followed by a 4-month daily continuation phase with isoniazid and rifampin) is as effective and as acceptable as the standard 9-month daily course of therapy (with isoniazid, rifampin, and ethambutol given for a 2-month initial intensive phase followed by a 7-month daily continuation phase with isoniazid and rifampin). The duration of short-course chemotherapy cannot be further reduced for smear-negative and culture-positive or smear-negative and culture-negative pulmonary tuberculosis or for extrapulmonary tuberculosis. Isoniazid has been demonstrated to be active as prophylactic therapy for tuberculosis at a daily dose of 300 mg (5-10 mg/kg in children) for 6-12 months. Prophylaxis of 2 months' duration with daily administration of isoniazid, rifampin, and pyrazinamide may be as effective as prophylactic therapy with isoniazid of 12 months' duration.