In this episode, I’ll discuss an article about the incidence of acute kidney injury with the use of nafcillin versus oxacillin.
Nafcillin and oxacillin are both antistaphylococcal penicillins used for the treatment of MSSA infections. Efficacy, cost, spectrum of activity, and pharmacokinetics are all similar between these two antibiotics. So much so that they are considered interchangeable and hospital formularies routinely only include one of these agents.
However, evidence has been building for some time that suggests the safety profiles of these two antibiotics are not identical, especially when it comes to rates of acute kidney injury, which may be higher with nafcillin. A group of authors published in Pharmacotherapy a retrospective cohort study looking at the incidence of acute kidney injury with the use of nafcillin versus oxacillin.
Data from over 600 patients were analyzed. About 25% of the patients received nafcillin and the rest oxacillin. 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.
Acute kidney injury occured in one-third of the patients who received nafcillin compared with just one-fifth of those who received oxacillin. This difference was statistically significant. The adjusted risk ratio for those receiving nafcillin was 1.55. 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.
The authors concluded:
In this study, nafcillin was associated with a significantly higher incidence of AKI than oxacillin.
This data in addition to other studies suggest that the two antibiotics are not interchangeable from an adverse effect point of view, and while the data is retrospective in nature, since efficacy is the same it would seem that this is enough evidence for a formulary change in those hospitals still using nafcillin.
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