Urinary prophylaxis with trimethoprim and trimethoprim-sulfamethoxazole: efficacy, influence on the natural history of recurrent bacteriuria, and cost control

Abstract

Low-dose trimethoprim (TMP), trimethoprim-sulfamethoxazole (TMP-SMZ), and nitrofurantoin macrocrystals were found to be safe and effective as prophylaxis against recurrent urinary tract infections. Women given placebo had 2.8 infections per patient-year during the six-month study period, while women given TMP, TMP-SMZ, or nitrofurantoin had significantly lower infection rates (0.015 per patient-year). The effect of prophylaxis appeared to be limited to the period when the agents were taken. Only one patient had a TMP-resistant coliform isolated from cultures obtained during prophylaxis and six months afterwards. The sole factor associated with the recurrence of infection after prophylaxis was a history of three or more infections in the year preceding prophylaxis. Thirty-one of the 60 women in the trial were monitored for a mean of 6.1 years before and 3.2 years after they entered the study. Analysis of infection rates indicated that about half these women were experiencing an infection cluster when they entered the study and that the prestudy baseline infection rate correlated with the poststudy rate. Thus, prophylaxis did not appear to exert a long-term effect on the baseline infection rate. Urinary prophylaxis generally appears to become cost-effective when the baseline infection rate exceeds two per patient-year.