133. Hypokalemia and Acute Kidney Injury Leading to Drug Discontinuation Occur More Commonly among Patients Receiving Nafcillin Compared to Oxacillin
Session: Poster Abstract Session: Antimicrobial Stewardship: Adverse Drug Events
Thursday, October 8, 2015
Room: Poster Hall
  • Nafcillin poster - FINAL.pdf (125.6 kB)
  • Background: Nafcillin (NAF) and oxacillin (OXA) are both recommended by consensus guidelines and used interchangeably at our center to treat MSSA infections. Based on clinical observations, we hypothesized that hypokalemia and other adverse events occur more often among patients (pts) receiving NAF.

    Methods: Retrospective cohort study of pts receiving 12g/day (d) of NAF or OXA for at least 24h between 4/2012 and 7/2013. Pts were followed until treatment discontinuation (DC) or discharge from the hospital. Those with pre-existing hypokalemia (K <3.4 mmol/L), liver disease (LFTs > 3x normal), or end-stage renal disease (requiring HD) were excluded.  

    Results: Of 224 pts included, 64% were male; median age was 64 yrs (range: 19 – 90). 71% and 29% received NAF and OXA, respectively. Charlson comorbidity scores, baseline serum creatinine (SCr), and receipt of concomitant medications did not differ between groups.  42% developed hypokalemia (defined as K ≤3.3) at a median of 4d (1 – 15) from start of therapy. Rates of hypokalemia were 51% and 17% for pts receiving NAF and OXA, respectively (P<0.0001). When defined as ≥ 0.5 mmol/L decrease in K, rates were 56% and 34%, respectively (P=0.005). Severe hypokalemia (K ≤ 2.9) was also more common among pts receiving NAF (20%) compared to OXA (3%, P=0.0008); by multivariable logistic regression, NAF was a predictor of K ≤2.9 (OR=6.74, 95% CI=1.45-31.2, P=0.02). There were no differences in rates of abnormal LFTs (P=0.45), hypersensitivity reactions (P=0.28), or leukopenia (P=0.49); however, 18% and 6% of pts developed acute kidney injury (AKI; increased SCr ≥ 1.5x baseline) after receipt of NAF and OXA, respectively (P=0.03).  Adverse events led to drug DC in 18% receiving NAF vs 2% receiving OXA (P=0.0004).  DC was secondary to AKI (50%), hypokalemia (40%), leukopenia (7%), and hypernatremia (3%). DC due to AKI and hypokalemia occurred exclusively among pts receiving NAF. Hypokalemia resolved in 86% of pts switched from NAF to OXA. Hospital re-admission within 30d did not vary by drug (28% vs 22%; P=0.38).   

    Conclusion: Comparing similar patient populations, those receiving NAF (compared to OXA) experienced higher rates of hypokalemia and AKI, which lead to treatment DC in 18%. Prospective studies validating these findings are warranted. Until such time, we recommend OXA as the preferred anti-staphylococcal penicillin.

    J. Alexander Viehman, MD1, Louise-Marie Oleksiuk, PharmD, BCPS2, Kathleen Sheridan, DO1,3, Karin Byers, MD, MS1,3, Peimei He, MD4, Bonnie Falcione, PharmD, BCPS AQ-ID1,2,3 and Ryan K. Shields, PharmD1,3, (1)Infectious Disease, University of Pittsburgh, Pittsburgh, PA, (2)Pharmacy and Therapeutics, UPMC, Pittsburgh, PA, (3)UPMC OPAT Program, Pittsburgh, PA, (4)Medicine, UPMC, McKeesport, PA


    J. A. Viehman, None

    L. M. Oleksiuk, None

    K. Sheridan, None

    K. Byers, None

    P. He, None

    B. Falcione, Hospira: Investigator , Co-investigator for an unrelated research study for which financial support was provided to the University of Pittsburgh

    R. K. Shields, Merck: Investigator , Research grant
    Astellas: Investigator , Research grant

    Findings in the abstracts are embargoed until 12:01 a.m. PDT, Wednesday Oct. 7th with the exception of research findings presented at the IDWeek press conferences.