A Controlled Study of Antimicrobial Prophylaxis of Recurrent Urinary Infection in Women

Twenty-seven adult women and thirteen girls with recurrent urinary infections were treated to eradicate their infection and then observed for recurrences while sequentially receiving three prophylactic drug regimens and a period with no drug therapy. The prophylactic regimens consisted of sulfamethoxazole, 500 mg daily, methenamine mandelate, 2 g daily, together with ascorbic acid 2 g daily, or trimethoprim, 40 mg, in combination with sulfamethoxazole, 200 mg daily. Children received half the adult doses. Thirty-three infections (3.6 per patient-year) occurred in patients on no drug therapy, 22 (2.5 per patient-year) in those taking sulfamethoxazole, 13 (1.6 per patient-year) in those taking methenamine mandelate and ascorbic acid, and 1 (0.1 per patient-year) in those taking trimethoprim–sulfamethoxazole. Trimethoprim–sulfamethoxazole was also the most effective in preventing colonization of the periurethral area with enterobacteriaceae. These results suggest that a daily low dose of trimethoprim–sulfamethoxazole is effective in preventing reinfections of the urinary tract in females. (N Engl J Med 291:597–601, 1974)