Controlled trial of 2, 4, and 6 months of pyrazinamide in 6-month, three-times-weekly regimens for smear-positive pulmonary tuberculosis, including an assessment of a combined preparation of isoniazid, rifampin, and pyrazinamide. Results at 30 months. Hong Kong Chest Service/British Medical Research Council.

In a study in Hong Kong 1,386 Chinese patients with sputum smear-positive pulmonary tuberculosis were allocated at random to four 6-month regimens of chemotherapy, all given three times weekly from the start and all containing isoniazid (H) and rifampin (R) throughout. Three contained streptomycin (S) for the first 4 months and pyrazinamide (Z) for 2 months (Z2), 4 months (Z4), or 6 months (Z6); the fourth contained pyrazinamide for 6 months but no streptomycin (Z6noS). Every dose of all four regimens was given under the direct supervision of clinic staff on a predominantly outpatient basis. During the later part of the intake patients were allocated at random to be given their HRZ either as a combined formulation (Rifater), each tablet containing 125 mg isoniazid, 100 mg rifampin, and 375 mg pyrazinamide, or as the three drugs separately. Among 892 assessable patients with drug-susceptible strains of tubercle bacilli pretreatment, bacteriologic failure during chemotherapy occurred in 4, all Z6noS (2% of 224; p less than 0.005 for the comparison with the S-containing regimens). During 30 months of follow-up after the end of chemotherapy, bacteriologic relapse occurred in 2 (3%) of 71 Z2, 2 (3%) of 72 Z4, 4 (6%) of 66 Z6, and 6 (9%) of 64 Z6noS patients allocated to Rifater, and in 4 (3%) of 149 Z2, 8 (6%) of 133 Z4, 2 (1%) of 142 Z6, and 6 (4%) of 135 Z6noS patients allocated to separate drugs. In the relapse rates there were no significant differences between the Rifater and separate drug regimens, the different durations of pyrazinamide, or the regimens with and without streptomycin.(ABSTRACT TRUNCATED AT 250 WORDS)