A Cochrane review included 15 trials involving a total of 1 644 elderly women. 5 trials compared single dose with short-term treatment (3–6 days), 3 studies single dose with long-term treatment (7–14 days) and 6 trials short-term with long-term treatment. Only 7 trials compared the same antibiotic given for a different length of time.
There was a significant difference for persistent UTI between single dose and short-course treatment (RR 2.01, 95% CI 1.05 to 3.84) and single versus long-course treatment (RR 1.93, 95% CI 1.01 to 3.70), in the short-term (< 2 weeks post-treatment) but not at long-term follow-up or on clinical outcomes. Patients preferred single dose treatment (RR 0.73, 95% CI 0.66 to 0.88), however this was based on only one trial comparing the same antibiotic. The comparison of short (3–6 days) and longer treatments (7–14 days) did not show any significant difference. Rate of adverse drug reactions increased significantly with longer treatment durations in only one study.
Comment: The quality of evidence is downgraded by study quality (different shortcomings in original studies) and by indirectness (differences in studied patients).