Retrospective Analysis of Adverse Drug Events Between Nafcillin Versus Cefazolin for Treatment of Methicillin-Susceptible Infections.

Nafcillin or cefazolin are drugs of choice for methicillin-susceptible (MSSA) infections. Prior studies indicate a higher incidence of acute kidney injury (AKI) with nafcillin, although AKI classification and time to occurrence is not well described. To characterize the incidence and time to adverse drug events for nafcillin versus cefazolin in the inpatient setting. A retrospective cohort study evaluated hospitalized, adult patients receiving intravenous nafcillin or cefazolin for treatment of MSSA infection. Incidence and time to AKI based on RIFLE criteria were measured. Secondary end points included antibiotic discontinuation and incidence of neutropenia, thrombocytopenia, elevated transaminases, and infection (CDI). Of 324 patients who received nafcillin (n = 119) or cefazolin (n = 205), higher rates of AKI were found for nafcillin versus cefazolin (19% vs 2%, respectively; < 0.0001). Median time to AKI with nafcillin was 6.5 days (range, 3-14 days). The majority of patients were classified as RIFLE "Risk" stratum. Nafcillin treatment discontinuations were more frequent than for cefazolin (17.6% vs 0.9%, respectively; < 0.0001). Nafcillin was an independent predictor of AKI (odds ratio = 12.4; 95% CI = 4.14-47.60, < 0.0001). No differences in neutropenia, thrombocytopenia, elevated transaminases, or CDI were observed. Nafcillin displayed higher rates of AKI at a median of 1 week of therapy, which provides a framework for clinician monitoring and consideration of antibiotic modification. Most patients developed "Risk" class AKI (RIFLE classification), which may be reversible with prompt intervention.