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Antimicrobial treatment of cystitis

Bandolier #13 carried a report [1] from a recent issue of JAMA concerning a randomised controlled trial of various antimicrobial drugs in the treatment of cystitis in young women. The study, which included an interesting economic analysis, concluded that trimethoprim-sulfamethoxazole produced the highest cure rate of drugs tested and was cheapest. Trimethoprim alone was not tested.

A number of readers have pointed out that there is no convincing evidence that this combination is any more effective than trimethoprim alone, and that the combination may carry a higher rate of adverse effects, especially in the elderly. They also point out that present prescribing policies in the UK favour trimethoprim alone rather than the combination, and that prescribing advice to GPs is to restrict their use of Co-trimoxazole on the grounds of safety.

Trimethoprim vs. Co-trimoxazole

A randomised controlled double blind trial of trimethoprim alone versus co-trimoxazole [2] showed no difference in efficacy between the two treatments in the urinary tract infection. Overall results in general practice patients, hospital patients and pregnant women gave an overall cure rate for trimethoprim of 89% (59 of 66 patients) and 84% (58 of 69 patients) with Co-trimoxazole.

Adverse effects were worse for Co-trimoxazole, where 17 of 83 patients treated (21%) had unwanted effects. With trimethoprim only 7 of 84 patients treated (8%) had unwanted effects.

More adverse effects with Co-trimoxazole

DTB in 1986 [3] indicated that deaths from Co-trimoxazole and trimethoprim were rare - about 1 per million prescriptions. About 80% were due to blood dyscrasias and 20% to skin reactions. With Co-trimoxazole deaths per million were 15 times higher in patients aged 65 or over than in those under 40 years.

With trimethoprim, DTB indicated that there were no reports of toxic epidermal necrolysis.

First choice

The MeReC Bulletin [4] looked at simple urinary tract infections in 1990. It concluded that trimethoprim is an appropriate first choice treatment, a view confirmed by more recent reviews [5].

Pharmaceutical advisers to FHSAs throughout the UK have been attempting to persuade GPs to restrict their use of Co-trimoxazole. Bandolier > is indebted to Dr Bryn Davies of the South Glamorgan Health Authority for pointing out that this is one topic where pharmaceutical advisers have been successful, with prescriptions by GPs in wales dropping significantly in 1994.

Bandolier thanks all those who wrote about this topic and pointed out what one correspondent called "a fall from grace"!


  1. 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.
  2. W Brumfitt, R Pursell. Double-blind trial to compare ampicillin, cephalexin, co-trimoxazole, and trimethoprim in treatment of urinary infection. British Medical Journal 1972 2: 673-6.
  3. Co-trimoxazole, or just trimethoprim? Drug and Therapeutics Bulletin 1986 24: 17-19.
  4. Simple urinary tract infections. MeReC Bulletin 1990 1: 21-3.
  5. M Gill. Use of sulphonamides and trimethoprim today. Prescriber 1995 Feb 5: 55-62.

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