Short-course tuberculosis chemotherapy studies conducted in Poland during the past decade

During the past decade, six short-course (6-month) chemotherapy regimens were studied in which drugs were given daily and intermittently. Four regimens containing isoniazid, rifampin, and ethambutol caused little toxicity but yielded relapse rates (8-21%) which were unacceptably high. The safety of giving rifampin (450 or 600 mg) twice weekly was confirmed, however, and there was evidence that daily therapy during the 4-month continuation phase was no more effective than twice weekly isoniazid and rifampin. Once weekly therapy during the continuation phase was clearly inadequate. The use of four drugs (isoniazid, rifampin, pyrazinamide, and streptomycin) given daily during the initial 2 months of therapy followed by 4 months of twice weekly isoniazid and rifampin resulted in a nearly 100% cure rate. However, this regimen was not well tolerated by patients. Deleting streptomycin improved the tolerability of the regimen but appears to have slightly increased the frequency of treatment failure and relapse. A suggested model for choosing treatment regimens is presented.