Postcoital antimicrobial prophylaxis for recurrent urinary tract infection. A randomized, double-blind, placebo-controlled trial.

We conducted a randomized, double-blind, placebo-controlled study to determine the efficacy of postcoital antibiotic prophylaxis in healthy young women prone to recurrent urinary tract infections. Sixteen patients were randomized to receive postcoital administration of a combination product of trimethoprim and sulfamethoxazole, while 11 received postcoital placebo. The treatment groups were similar with respect to age, parity, diaphragm use, history of lifetime urinary tract infections, frequency of intercourse, and number of lifetime sexual partners. In over 6 months of observation, postcoital administration of trimethoprim-sulfamethoxazole was highly effective in preventing recurrent urinary tract infections. Nine of 11 patients who took the placebo developed urinary tract infections (infection rate, 3.6 per patient-year), compared with only two of 16 patients who received postcoital trimethoprim-sulfamethoxazole (infection rate, 0.3 per patient-year). Postcoital administration of trimethoprim-sulfamethoxazole was effective in patients with both low (two or fewer times per week) and high (three or more times per week) intercourse frequencies. Side effects were few and compliance was excellent. We conclude that postcoital trimethoprim-sulfamethoxazole is a safe, effective, and inexpensive approach to management of recurrent urinary tract infections in young women.