A Cochrane review included 8 studies with a total of 618 subjects. The duration of antibiotic prophylaxis treatment varied from 10 weeks to 12 months.
Compared to placebo/no treatment (5 studies, n=406), antibiotics reduced the risk of repeat positive urine culture (RR 0.44, 95% CI 0.19 to 1.00; RD –30%, 95% CI –56% to –4%). One study reported that nitrofurantoin was more effective than trimethoprim in preventing recurrent UTI over a six month period (RR 0.48, 95% CI 0.25 to 0.92; RD –18%, 95% CI –34% to –3%). However, patients receiving nitrofurantoin were more likely to discontinue the antibiotic due to side effects (mainly gastrointestinal) (RR 3.17, 95% CI 1.36 to 7.37; RD 22%, 95% CI 8% to 36%). The other study found cefixime was more effective in preventing recurrent UTI than nitrofurantoin (RR 0.74, 95% CI 0.13 to 4.10; RD –3%, 95% CI –17% to –12%). However, 62% of patients receiving cefixime experienced an adverse reaction during the first six months of treatment (18/29) while only 26% (8/31) of patients receiving nitrofurantoin reported an adverse reaction.
Comment: The quality of evidence is downgraded study quality (inadequate or unclear allocation concealment, inadequate intention-to-treat adherence) and by possibility of reporting bias.