Assessment of a daily combined preparation of isoniazid, rifampin, and pyrazinamide in a controlled trial of three 6-month regimens for smear-positive pulmonary tuberculosis. Singapore Tuberculosis Service/British Medical Research Council.

In a study in Singapore 310 patients with sputum smear-positive pulmonary tuberculosis were allocated at random to daily chemotherapy with streptomycin, isoniazid, rifampin, and pyrazinamide (1) for 2 months (2SHRZ), (2) for 1 month (1SHRZ), or (3) for 2 months without streptomycin (2HRZ). This was followed for all patients by three times weekly isoniazid and rifampin to a total duration of 6 months. During the initial period of daily chemotherapy the patients were also allocated at random to be given their HRZ either as a combined formulation (Rifater), each tablet containing 50 mg isoniazid, 120 mg rifampin, and 300 mg pyrazinamide, or as three separate drugs. During the Rifater versus separate drugs comparison the most common spontaneous complaints were of nausea and vomiting, reported by 8% of 155 patients receiving Rifater and 7% of 155 separate drugs. Other adverse effects were also reported in similar proportions in the two series. Among 271 patients with drug-susceptible strains of tubercle bacilli pretreatment there were no bacteriologic failures during chemotherapy. During 18 months of subsequent follow-up bacteriologic relapse occurred in 3 (7%) of 46 2SHRZ, 2 (5%) of 42 1SHRZ, and 3 (8%) of 40 2HRZ patients allocated to Rifater and in 0 of 47 2SHRZ, 1 (2%) of 46 1SHRZ, and 1 (2%) of 44 2HRZ patients allocated to separate drugs. There was no evidence of therapeutic benefit from continuing SHRZ administration beyond 1 month or from adding streptomycin to HRZ. The relapse rates were slightly higher in the Rifater series (p = 0.04). Further follow-up and results from other studies are therefore needed fully to assess the combined preparation.