USPHS Tuberculosis Short-Course Chemotherapy Trial 21: effectiveness, toxicity, and acceptability. The report of final results.

<bold>Study Objective: </bold>To determine the effectiveness, toxicity, and acceptability of a 6-month antituberculous regimen compared with a 9-month regimen.<bold>Design: </bold>A nonblinded, unbalanced, randomized, multicenter clinical trial.<bold>Setting: </bold>Twenty-two tuberculosis clinics in public health departments and hospitals in the United States.<bold>Patients: </bold>Patients were eligible if Mycobacterium tuberculosis, isolated from sputum cultures, was susceptible to study drugs. Of 1451 patients enrolled, 75% (617 of 823) assigned to the 6-month regimen and 71% (445 of 628) assigned to the 9-month regimen were eligible.<bold>Interventions: </bold>Patients took self-administered isoniazid and rifampin daily for 24 weeks (6-month regimen) or 36 weeks (9-month regimen). In addition, patients assigned to the 6-month regimen took self-administered pyrazinamide daily during the first 8 weeks.<bold>Results: </bold>Patients on the 6-month regimen converted more rapidly than patients on the 9-month regimen (94.6% compared with 89.9% after 16 weeks of therapy, with a difference of 4.7% [95% CI, 0.7% to 8.7%]); had similar rates of adverse drug reactions (7.7% compared with 6.4%, with a difference of 1.3% [95% CI, 0.0% to 4.6%]); had lower noncompliance rates (16.8% compared with 29.2%, with a difference of 12.4% [95% CI, 6.8% to 18.0%]); and had similar relapse rates 96 weeks after completing therapy (3.5% compared with 2.8%, with a difference of 0.7% [95% CI, 0.0% to 3.9%]). A significantly greater proportion of patients assigned to the 6-month regimen successfully completed therapy (61.4% compared with 50.6%; chi 2 = 11.976).<bold>Conclusions: </bold>Our results suggest that this 6-month regimen is similar in effectiveness, toxicity, and acceptability to the 9-month regimen for treating pulmonary tuberculosis. [ABSTRACT FROM AUTHOR]