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Drug Watch: Antimicrobial Treatment of Cystitis

Urinary tract infections in women are a common reason for GP visits, and GPs use a large number of different antimicrobials for widely different times. A randomised controlled trial of four antimicrobial three-day regimens may help to put some evidence behind treatment.

The setting

The study was carried out in Seattle among young women presenting to the University of Washington Student Health Centre. They had symptoms of acute cystitis including dysuria, frequency, urgency and/or suprapubic pain. E coli was the most common pathogen (85%), and no patient had chlamydia or gonorrhoea at enrolment.

The design

Treatments were randomised but not blind. Each was for three days, and they were:-
  • trimethoprim-sulphamethoxazole, 160 mg/800 mg, twice daily (co-trimoxazole in the UK).
  • macrocrystalline nitrofurantoin, 100 mg four times a day.
  • cefadroxil, 500 mg twice daily
  • amoxycillin, 500 mg three times daily

Patients were seen before treatment began, at 4-6 days, 2 weeks after treatment and 4-6 weeks after treatment.

A genitourinary history was taken on each occasion and a mid-stream urine was collected for culture.

The Results

Trimethoprim-sulphamethoxazole proved to be the best treatment, with 82% of women cured at the six-week visit, and with the lowest remaining incidence of vaginal E coli (21%). Adverse events were reported by 35% of patients treated with trimethoprim-sulphamethoxazole, similar to other treatments.

The study also performed an economic analysis, showing that treatment with trimethoprim-sulphamethoxazole was the least costly. Though drug costs will be different in the UK, the higher costs of the less effective treatments were associated with more frequent visits to the clinic for treatment of recurrent urinary tract infection.

In the UK, the cost of three-days course of the drugs is lowest for trimethoprim-sulphamethoxazole(co-trimoxazole; £0.42); for nitrofurantoin it is £0.48, for amoxycillin £0.75 and for cephadroxil £1.69), without dispensing fees.


The cheapest drug works best - and probably results in fewer women returning because of inefficacy.


TM Hooton, C Winter, F Tiu, WE Stamm. Randomized comparative trial and cost analysis of 3-day antimicrobial regimens for treatment of acute cystitis in women. Journal of the American Medical Association 1995 273: 41-5.

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