Antibiotic Better Than Cranberries for UTI Prevention

From Medscape Medical News

Laurie Barclay, MD

July 26, 2011 — Trimethoprim-sulfamethoxazole (TMP-SMX) is more effective than cranberry capsules for prevention of recurrent urinary tract infection (UTI) in premenopausal women, according to the results of a double-blind, double-dummy noninferiority trial reported in the July 25 issue of the Archives of Internal Medicine.
"The increasing prevalence of uropathogens resistant to antimicrobial agents has stimulated interest in cranberries to prevent recurrent ...UTIs," write Mariëlle A. J. Beerepoot, MD, from the Academic Medical Center in Amsterdam, the Netherlands, and colleagues.
"For premenopausal women with more than 2 UTIs per year, low-dose antibiotic prophylaxis is commonly recommended. However, this may lead to drug resistance not only of the causative microorganisms but also of the indigenous flora."
In this study, 221 premenopausal women with recurrent UTIs were randomly assigned to receive prophylaxis with TMP-SMX, 480 mg once daily, or cranberry capsules, 500 mg twice daily, for 12 months.
The main study outcomes were the mean number of symptomatic UTIs during the 12-month period of prophylaxis, the proportion of women who had 1 or more symptomatic UTIs, the median time to first UTI, and development of antibiotic resistance in indigenous Escherichia coli.
Compared with the TMP-SMX group, the cranberry group had a higher mean number of patients with at least 1 symptomatic UTI after 12 months (4.0 vs 1.8; P = .02) and a higher proportion of patients with at least 1 symptomatic UTI (78.2% vs 71.1%). In the cranberry group, median time to the first symptomatic UTI was 4 months, compared with 8 months in the TMP-SMX group.
TMP-SMX resistance after 1 month was present in 23.7% of fecal and 28.1% of asymptomatic bacteriuria E coli isolates in the cranberry group, compared with 86.3% and 90.5%, respectively, in the TMP-SMX group. Resistance rates for trimethoprim, amoxicillin, and ciprofloxacin in these E coli isolates after 1 month were also increased in the TMP-SMX group. When TMP-SMX was discontinued, resistance returned to baseline levels after 3 months.
In the cranberry group, antibiotic resistance did not increase. Participants tolerated cranberries and TMP-SMX equally well.
"In premenopausal women, TMP-SMX, 480 mg once daily, is more effective than cranberry capsules, 500 mg twice daily, to prevent recurrent UTIs, at the expense of emerging antibiotic resistance," the study authors write.
Limitations of this study include high withdrawal rates, lack of microbiological confirmation of all recurrent UTIs, inability to confirm that all women took the cranberry prophylaxis, and unclear optimal dosage of cranberries.
"From clinical practice and during the recruitment phase of this study, we learned that many women are afraid of contracting drug-resistant bacteria using long-term antibiotic prophylaxis and preferred either no or nonantibiotic prophylaxis," the study authors concluded.
"In those women, cranberry prophylaxis may be a useful alternative despite its lower effectiveness."
An invited commentary by Bill J. Gurley, PhD, from the University of Arkansas for Medical Sciences, Little Rock, notes that the comparison may not have been fair regarding dose and bioavailability of active ingredients.
"To date, few botanical dietary supplements have lived up to their claims as effective 'alternative' medicines, and until more is known about phytochemical disposition in humans, efficacy concerns will continue to plague these products," Dr. Gurley writes.
"Uncertainty regarding mechanisms of action and adequate dosing regimens underscore many of these concerns. It would appear, however, that cranberry has the potential to dispel some of this uncertainty."


Arch Intern Med. 2011;171:1270-1278, 1279-1280.