LAUSR

Abstract Background Antistaphylococcal penicillins including oxacillin and nafcillin are among the drugs of choice for severe and invasive MSSA infections. While alternative agents such as cefazolin are associated with improved safety compared with antistaphylococcal penicillins, comparative safety data between individual antistaphylococcal penicillins is limited and has shown possible improved safety with oxacillin among adults. The objective of this study was to determine the relative adverse events (AEs) reporting for these agents among the FDA Adverse Event Reporting System (FAERS) database. Methods We reviewed adverse events reports from the FAERS database from Q4/2003-Q1/2018 and performed a disproportionality analysis of safety events for nafcillin and oxacillin including ADEs related to acute kidney injury (AKI), rash, hypokalemia, and hepatotoxicity. Measures of association evaluated included reporting odds ratio (ROR) and proportion reporting ratio (PRR). Results Reports of AKI were substantially more common with nafcillin (PRR 23.2, 95% CI 18.4––29.3) than oxacillin (PRR 10.9, 95% CI 7.6––15.5). Rash was slightly higher with nafcillin than oxacillin (PRR 3.7, 95% CI 2.8––5.1 vs. 2.6, 95% CI 1.8––3.8). Hypokalemia was substantially more common with nafcillin than oxacillin (PRR 11.8, 95% CI 7.1––19.4 vs. 1.6, 95% CI 0.4––6.4). Hepatotoxcitiy was slightly higher reported among nafcillin than oxacillin (PRR 25.3, 95% CI 14.5––44.3 vs. 12.9, 95% CI 5.8––28.6). Similar observations were seen with RORs (Figure 1).Figure 1. Reporting Odds Ratios of AEs with Nafcillin and Oxacillin Conclusion Oxacillin may be associated with overall improved safety compared with nafcillin based on reporting signals from FAERS. Our results support previous limited observational data. With the likely equal efficacy of these agents, clinicians may want to consider prescribing oxacillin over nafcillin if an antistaphylococcal penicillin is indicated for an invasive MSSA infection. However, given the limitations of reporting systems, further evaluation is warranted. Disclosures All authors: No reported disclosures.