Minimum effective dose of trimethoprim for urinary tract infection.

Non-pregnant women with urinary tract infection attending a health centre were treated with single doses of 400 mg, 200 mg or 100 mg of trimethoprim. The cure rates for these doses were 100%, 93% and 90%, respectively. In general practice the expected cure rate for this infection treated conventionally over five to seven days is 85-90%. Therefore, 100 mg of trimethoprim is the minimum effective dose for the treatment of urinary tract infection in general practice.