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Premenopausal women who experience recurrent urinary tract infections (UTIs) are sometimes prescribed low-dose antibiotic prophylaxis. Growing concern about antibiotic resistance, coupled with many patients' desire for nonpharmacologic remedies, has led to renewed interest in cranberry consumption for UTI prophylaxis. The presumed mechanism is prevention of bacterial adhesion to uroepithelial cells by proanthocyanidins, a constituent of cranberries.
In a double-blind study, Dutch investigators randomized 221 women (median age, 35) who reported having a median of 6 to 7 UTIs in the previous year to receive either cranberry extract (500 mg twice daily) or trimethoprim-sulfamethoxazole (TMP-SMX; 480 mg nightly). During 12 months of treatment, cranberry-extract recipients had a mean of 4 symptomatic UTIs compared with a mean of 1.8 in the TMP-SMX group — a significant difference; the median time to first recurrence was 4 months in the cranberry group and 8 months in the antibiotic group. Adverse events did not differ between groups, but the dropout rate was about 50% in both.
Beerepoot MAJ et al. Cranberries vs antibiotics to prevent urinary tract infections: A randomized double-blind noninferiority trial in premenopausal women. Arch Intern Med 2011 Jul 25; 171:1270. (http://dx.doi.org/10.1001/archinternmed.2011.306)
Gurley BJ. Cranberries as antibiotics? Arch Intern Med 2011 Jul 25; 171:1279. (http://dx.doi.org/10.1001/archinternmed.2011.332)
Comment
Whereas cranberry extract recipients had fewer UTIs than they did in the preceding year, TMP-SMX was more effective. However, antibiotic resistance to TMP-SMX developed in >85% of Escherichia coli strains in women taking the antibiotic, compared with <30% in those taking cranberry extract. Unfortunately, cranberry juice was no better than placebo for preventing UTIs in a recent study (JW Gen Med Jan 20 2011); whether cranberry or one of its constituents ultimately will prove to be clinically useful remains unclear.