We studied 30 women with a history of at least 3 documented urinary tract infections within the previous year who were treated with 500 mg. cinoxacin or a placebo nightly for 6 months. Of the 17 patients on cinoxacin therapy 12 remained abacteriuric for 6 months and 2 remained abacteriuric for 1 and 5 months, respectively, but were withdrawn from the study because an allergic skin rash developed. In 3 patients recurrent urinary tract infections developed within 2 months with strains resistant to cinoxacin. Of the 13 patients in the placebo group 9 remained abacteriuric for 6 months and recurrent urinary tract infections developed in 4 within 3 months. After cinoxacin therapy recurrent infections occurred in 10 of 17 patients compared to 5 of 13 for placebo. The incidence of infection in the group treated with cinoxacin was not significantly different from the incidence in the placebo group. During cinoxacin treatment 32.2 per cent of monthly vaginal and 62.2 per cent of monthly fecal cultures yielded Enterobacteriaceae compared to 49.6 and 92.8 per cent, respectively, for placebo. Enterobacteriaceae resistant to cinoxacin occurred in no vaginal cultures during and for 30 days after therapy, while 5 of 98 (5.1 per cent) fecal cultures from 3 patients yielded new resistant bacteria. These results are at variance with the reported efficacy of cinoxacin for prevention of recurrent urinary tract infections. The low order of bacterial resistance suggests that further controlled studies are warranted to establish the role of cinoxacin in the prevention of recurrent urinary tract infections.
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