Double-blind multicenter trial of a rifampicin-trimethoprim combination and rifampicin alone in urinary tract infections.

A double-blind multicenter trial was carried out in 146 patients with urinary tract infections in order to compare the combination of rifampicin and trimethoprim (450 mg plus 120 mg twice daily) with rifampicin alone (450 mg twice daily). The success rate on the day after a 10-day course of treatment was significantly higher after the combination than after rifampicin alone (72% of 60 cases vs. 45% of 55 cases). The difference was still significant, and of the same order of magnitude, 1 week after the end of the treatment (53% of 51 vs. 24% of 45 cases). The subgroups of patients with organisms sensitive to both rifampicin and trimethoprim before treatment was considered separately in each treatment group: rifampicin-resistant strains were isolated after treatment in 27% of 26 patients treated with rifampicin alone, and in 7% of 27 patients in the other group. The tolerances of the two treatments were superimposable. The combination rifampicin-trimethoprim appears to overcome the problem of selection of rifampicin-resistant strains, with the concomitant therapeutic failures, in urinary tract infections.