Program Schedule

392
Vancomycin Dosing and Concentrations at a Large University-Affiliated County Hospital

Session: Poster Abstract Session: PK/PD Studies
Thursday, October 9, 2014
Room: The Pennsylvania Convention Center: IDExpo Hall BC
Posters
  • IDWeek poster final.pdf (365.8 kB)
  • Background: According to the IDSA guidelines, vancomycin trough concentrations are the most accurate and practical method for therapeutic drug monitoring (TDM). Methods: As part of a prospective, 3-year, sequential cohort study of a novel Bayesian vancomycin therapeutic drug monitoring (TDM) strategy, to establish the baseline TDM practice we enrolled 83 patients at our tertiary-care, academic, county hospital during the first year from 2012-2013. Results: Patients were 9 months to 74 years old. The first vancomycin concentration was therapeutic per IDSA guidelines in only 26 (31%) patients, with sampling in 54 (65%) after the 3rd or 4th dose, and before (20%) or after (15%) these doses in the rest. The median sample time after start of therapy was 35 hours (range 8-93 hours). Only 34 (41%) of samples were true troughs drawn within 1 hour before the next planned dose based on the dose interval, and 31 (39%) of 79 were drawn within 1 hour before the next actual dose (4 patients stopped vancomycin). The median true trough was 14.7 mg/L in therapeutic patients and 6.3 mg/L in those that were not therapeutic (p=0.0008). The median vancomycin dose was 12.5 mg/kg in patients with therapeutic troughs and 13.0 mg/kg in those without (p=0.88). In 6 (7%) patients with nephrotoxicity, the median vancomycin concentration was 18.1 mg/L vs. 11.3 mg/L in patients without renal injury (p=0.0001). Conclusion: Measurement of true steady-state vancomycin troughs within one hour of the next dose does not happen for the majority of patients in our hospital setting, biasing interpretation from traditional TDM or nomograms that depend on accurate timing. Therapeutic concentrations cannot be predicted from dosing, and non-therapeutic patients are more likely to be underdosed than overdosed. To prevent underdosing and nephrotoxicity from overdosing, routine use of a TDM approach that can handle sample timing variability, such as a Bayesian algorithm, is strongly justified by our data. Testing of the algorithm is ongoing in years 2 and 3 of our study.
    Gilmer Youn, MD1, Emi Minejima, PharmD2, Lironn Kraler, BS1, Brenda Jones, MD1 and Michael Neely, MD3, (1)School of Medicine, University of Southern California, Los Angeles, CA, (2)School of Pharmacy, University of Southern California, Los Angeles, CA, (3)Division of Pediatric Infectious Diseases, Childrens Hospital Los Angeles, Los Angeles, CA

    Disclosures:

    G. Youn, None

    E. Minejima, None

    L. Kraler, None

    B. Jones, None

    M. Neely, Applied Pharmacometrics: Co-founder, Seeking to eventually license a Bayesian dosing software program developed by the Laboratory of Applied Pharmacokinetics, of which I am director

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