ABSTRACT
Ninety-six elderly patients (mean age 80 years) with acute urinary infections were treated in a single-blind trial, with either one 200 mg dose of trimethoprim or 200 mg b.d. for five days. After one week the initial pathogen was eliminated in 67% of patients who had received the single dose and in 94% who received the drug for five days. These differences were highly significant (P less than 0.01). After two weeks, the patients who had received trimethoprim for five days were significantly freer from infection than those who had received the single dose. The level of acquired resistance following trimethoprim was small. The single dose of trimethoprim was associated with less suppression of the faecal Enterobacteriaceae and the selection of less resistance in these organisms than the five-day course. Interrupted antibiotic courses may not be particularly prone to select resistance. Trimethoprim was well tolerated in the great majority of patients; only three patients suffered possible side-effects.
