Clinical question: Does antibiotic prophylaxis prevent future episodes of urinary tract infections?
Background: Recurrent urinary tract infections (UTI) in children might be associated with renal scarring and subsequent clinical consequences associated with long-term morbidity. Historically, antibiotic prophylaxis has been recommended for children who might have risk factors for recurrent infection, most commonly vesicoureteral reflux. However, scars may be present in the absence of known risk factors and upon first UTI. The efficacy of antibiotic prophylaxis in preventing recurrent UTIs is unclear.
Study design: Randomized, double-blind, placebo-controlled trial.
Setting: Four centers in Australia.
Synopsis: The study looked at 576 children under the age of 18 with a history of at least one symptomatic UTI. The patients were randomized to receive trimethoprim-sulfamethoxazole (TMP-SMX) or placebo for 12 months. Children with vesicoureteral reflux were included, but those with known neurologic, skeletal, or urologic predispositions were excluded.
Thirteen percent of patients in the antibiotic group developed a UTI compared with 19% of patients in the placebo group (P=0.02). The authors calculate that at 12 months, 14 patients would need to be treated to prevent one UTI.
This study was unable to enroll the planned number of children but remained adequately powered to show a reduction in the primary outcome (rate of symptomatic UTI). However, a significant number of patients (approximately 28%) in each arm stopped taking the medication, the majority for undisclosed reasons. Despite an intention-to-treat analysis, this degree of dropout raises questions about the true effect size. Additionally, this study does not answer the more important clinical question regarding the effect of prophylaxis on potential future renal damage, specifically in children with vesicoureteral reflux.
Bottom line: Antibiotic prophylaxis might be modestly effective in preventing recurrent UTIs.
Citation: Craig JC, Simpson JM, Williams GJ, et al. Antibiotic prophylaxis and recurrent urinary tract infection in children. N Engl J Med. 2009;361(18):1748-1759.