Comparison of 4 and 10 days of doxycycline treatment for urinary tract infection.

A total of 105 ambulatory patients presenting with symptoms suggestive of cystitis was allocated randomly to a 4 or a 10-day course of doxycycline therapy. Of these patients 62 (59 per cent) had documented infections and 41 (66 per cent) were infected with doxycycline-sensitive organisms: 24 were randomized to a 4-day course and 17 to a 10-day course of antibiotic. The groups were similar with respect to age, history of urinary tract infection, bacteriology and site of infection. Of the 4-day treatment group 90 per cent were free of infection 42 days after completion of therapy, compared to 92 per cent in the 10-day treatment group. Thus, patients with symptoms of cystitis may be treated with a short course of an appropriate antibiotic, provided careful followup is made 4 to 6 weeks after cessation of therapy. The site of urinary infection of doxycycline-resistant and sensitive organisms was determined by the antibody-coated bacteria techniques in 56 episodes: 13 (23 per cent) originated in kidneys, 34 (61 per cent) originated in bladder foci and the results in 9 (16 per cent) were indeterminate. Results of the antibody-coated bacteria technique did not predict therapeutic outcome.