Incidence of Acute Kidney Injury With the Use of Nafcillin Versus Oxacillin

BACKGROUND: Antistaphylococcal penicillins (ASPs) are highly effective against infections caused by methicillin-susceptible Staphylococcus aureus (MSSA). Nafcillin and oxacillin are ASPs with similar spectra of activity, rates of efficacy, pharmacokinetic profiles, and cost. However, there is a growing body of evidence suggesting key distinctions between the safety profiles of nafcillin and oxacillin, including a higher rate of acute kidney injury (AKI) with nafcillin. This retrospective study aims to compare the rate of AKI with nafcillin versus oxacillin at a large academic medical center. METHODS: A retrospective cohort study was conducted including adult inpatients who were treated with at least six doses of oxacillin or nafcillin. The primary outcome was the incidence of AKI during treatment. Secondary outcomes included change in serum creatinine from baseline, AKI stage, duration of therapy, duration of hospitalization, and in-hospital mortality. Exploratory outcomes included the incidence of moderate hypokalemia, severe hypokalemia, and hepatotoxicity. RESULTS: Among 638 patients (171 on nafcillin, 467 on oxacillin), AKI occurred in 33.3% of patients in the nafcillin group compared to 19.5% in the oxacillin group (adjusted risk ratio 1.55, 95% confidence interval 1.16-2.06; p < 0.01). Nafcillin was associated with a greater incidence of AKI at each stage, longer duration of hospitalization, higher in-hospital mortality rate, and increased rates of moderate and severe hypokalemia compared to oxacillin. CONCLUSION: In this study, nafcillin was associated with a significantly higher incidence of AKI than oxacillin.