Comparison of renal function parameters and acute kidney injury incidence between vancomycin monotherapy and vancomycin-fosfomycin combination therapy in patients: a propensity score-matched analysis

Vancomycin (VAN) is a first-line agent for methicillin-resistant Staphylococcus aureus (MRSA) infections, but it poses nephrotoxicity risks. While VAN-fosfomycin (FOS) combination shows synergistic efficacy and lower mutant prevention concentrations, its renoprotective effects compared to VAN alone remain unclear. This study aims to directly compare renal function parameters and acute kidney injury incidence between VAN monotherapy and VAN + FOS combination therapy. After propensity score matching of the initial 156 patients, 76 individuals were included in the final analysis; 38 were assigned to the vancomycin monotherapy group and 38 in the VAN + FOS combination group. Renal function parameters were recorded at 48 h and 72 h post-treatment, and the incidence of acute kidney injury (AKI) was compared between the two groups. Univariate analyses were performed to identify baseline factors associated with AKI. The VAN + FOS group had a significantly lower incidence of AKI compared to the VAN-alone group (5.26% vs. 21.05%, P = 0.04). Due to the limited number of AKI cases, multivariate adjustment was not possible. Univariate analysis revealed significant associations between AKI incidence and FOS combination therapy, age, and vancomycin trough concentration (P = 0.04, P = 0.00, and P = 0.02, respectively). These findings warrant validation in larger, prospective studies. Fosfomycin adjunct therapy was associated with a lower incidence of vancomycin-induced AKI. However, these associations should be interpreted cautiously and require validation in larger cohorts.