Prophylaxis of recurring urinary tract infection in females: a comparison of nitrofurantoin with trimethoprim-sulfamethoxazole.

Twenty-eight females with recurrent urinary tract infection were treated to eradicate their existing infections and then observed for recurrences while receiving one of the three following prophylactic regimens for 6 to 12 months: nitrofurantoin, 50 mg daily; one half tablet of trimethoprim-sulfamethoxazole (TMP-SMX) twice weekly; or one tablet of TMP-SMX once weekly. Preadolescent girls received half the adult doses. After completion of the course of prophylactic agent the patients were followed up at bimonthly intervals until infection recurred. After eradication of this new infection they were started on another prophylactic regimen. Six infections (1.0/patient-year) recurred in patients on nitrofurantoin, four infections (0.4/patients-year) reucrred in those receiving twice weekly TMP-SMX, and 12 infections (1.3/patient-year) in those receiving once weekly TMP-SMX. The mean interval between discontinuation of prophylaxis and recurrence of infection was 2.6 months. TMP-SMX in the doses used eliminated aerobic gram-negative rods from swabs from the anal canal in many patients. Gram-negative organisms resistant to trimethoprim did not cause infection either during or after therapy.