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Cranberry extract an option in recurrent UTI

Urology

Urology

Cranberry should be considered for older women with recurrent UTIs who wish to avoid antibiotic therapy, the results of a small trial suggest.

Recurrent UTI is a common problem, currently managed with either repeated courses of antibiotics or long-term, low-dose antibiotic prophylaxis. Existing evidence suggests antibiotic prophylaxis is highly effective in older women, however, side-effects are relatively common, especially oral or vaginal thrush, and there is increasing interest in the role of cranberry in preventing infection.

This RCT looked at a population of women aged 45 or older with at least two episodes of UTI treated with antibiotics in the previous 12 months.

A total of 137 women were randomised, to one capsule of 500mg of cranberry extract at bedtime for 6 months (69) or one capsule of 100mg trimethoprim (68).

Thirty nine patients had a symptomatic UTI during the trial, 25 in the cranberry group, 14 in the trimethoprim group (RR 1.6, p=0.084). This was not statistically significant as the numbers were small but showed a convincing trend towards more infections in the cranberry group. Median time to recurrence of UTI was 84.5 days for cranberry versus 91 days for trimethoprim (p=0.48). Withdrawals from the trial were greater in the trimethoprim group (16%) than the cranberry group (9%) but this was again not statistically significant (p=0.20). The number of gastrointestinal upsets was the same in both groups.

The study did not demonstrate a significant difference between trimethoprim and cranberry in preventing UTIs. However the small size of this study and the 60% greater risk of developing a UTI in the cranberry group indicates that a larger study may well show statistical significance.

Although cranberry is likely to be less effective than antibiotic therapy, it is clearly an option for recurrent UTI in older women who prefer to avoid antibiotics, or who have been affected by oral or vaginal thrush as a side-effect of antibiotic treatment. Research suggests capsules to be at least as effective as juice, but capsules usually prove to be cheaper and more convenient.

While this is a useful small study, it would be interesting to see a large RCT comparing placebo versus cranberry versus antibiotic versus a combination of cranberry and antibiotic for a definitive comparison of the respective benefits of these treatment options.

McMurdo MET, Argo I, Phillips G et al. Cranberry or trimethoprim for the prevention of recurrent urinary tract infections? A randomized controlled trial in older women. J Antimicrob Chemoth 2009;63:389-395

Reviewer

Dr Jonathan Rees
GPwSI Urology, Bristol

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