Renal safety of amikacin compared with ceftriaxone in patients treated for urinary tract infection: an observational cohort study.

PURPOSE: Aminoglycosides are broad-spectrum antibiotics commonly used as monotherapy for urinary tract infections (UTIs). However, their use is often limited by concerns regarding nephrotoxicity. We compared the renal safety of amikacin with ceftriaxone in patients treated for UTI with or without bloodstream infection. METHODS: We conducted a single-center retrospective cohort study including adult patients hospitalized between April 2018 and March 2022 who received amikacin or ceftriaxone for UTI for 3-10 days. Patients were matched 1:1 according to age, duration of therapy, and baseline renal function. The primary outcome was acute kidney injury (AKI), defined according to KDIGO criteria. Analyses included Kaplan-Meier time-to-event analysis, propensity score-adjusted Cox regression, and multivariable logistic regression. Alternative etiologies for AKI were also assessed. RESULTS: A total of 138 matched pairs were included. Overall, 15 patients (5.4%) developed AKI: 9 (6.5%) in the amikacin group and 6 (4.3%) in the ceftriaxone group (P = 0.597), and Kaplan-Meier analysis likewise showed no difference between groups (log-rank P = 0.962). In propensity score-adjusted analysis of the total cohort, amikacin was not associated with increased risk of AKI (aHR 1.305, 95% CI 0.448-3.802, P = 0.626). Independent risk factors for AKI included institutional residence, higher Charlson comorbidity index, and bloodstream infection. Most AKI cases were mild and had alternative explanations. CONCLUSIONS: In this matched cohort, amikacin was not associated with a higher risk of AKI compared with ceftriaxone. These findings suggest that, in selected patients, amikacin may represent a safe carbapenem-sparing option. Further studies are needed to confirm these findings.