729. Probabilities of Achieving Therapeutic Vancomycin Trough Concentration in Obese versus Non-Obese Patients
Session: Poster Abstract Session: Antimicrobials: PK/PD Studies
Friday, October 4, 2013
Room: The Moscone Center: Poster Hall C
Posters
  • IDWeekPoster#729-Javaid.pdf (244.5 kB)
  • Background:

    Vancomycin (VAN) continues to be a commonly-used antibiotic for the treatment of methicillin-resistant Staphlococcus aureus (MRSA) infections.  Contemporary “therapeutic” trough concentrations are 10-20 mg/L (but ideally 15-20 mg/L), and sub- or supra-therapeutic concentrations have been associated with decreased efficacy or increased nephrotoxicity.  Obesity can significantly alter the pharmacokinetics of VAN, but conflicting data exist on the magnitude of the alterations, and minimal data exist on how to “best” dose VAN in patients with obesity. The goal of our investigation was to determine if current VAN dosing strategies at our hospital result in a significant difference in the % achievement of therapeutic VAN troughs for obese versus non-obese patients.

    Methods:

    This was a retrospective cohort study of adult inpatients (> 18 years of age) who were treated with VAN for at least 3 days and who had at least 1 serum vancomycin trough concentration obtained during the course of therapy.  Standard clinical and laboratory data were collected, and patients were classified as obese or non-obese based body-mass index (BMI) values.

    Results:

    Data were collected for a total of 56 patients (30 male, 26 female).  The average patient age was 63 years (range 26-102), 27% of patients had renal dysfunction (defined as a creatinine clearance of <40 ml/min at the start of VAN therapy), and 30% of patients were considered obese (BMI > 29.9).  Using a therapeutic range of 10-20 mg/L, the % of initial VAN troughs considered therapeutic / subtherapeutic / supratherapeutic were 46/46/8, respectively.  The % of initial VAN troughs considered therapeutic did not significantly differ between non-obese and obese patients (42% versus 47%), but obese patients had a higher % of supratherapeutic initial troughs than non-obese patients (23.5% versus 0%, P<0.01).  There also was a non-significant trend towards higher rates of nephrotoxicity in extremely-obese patients (BMI >39.9) versus non-obese patients (37.5% versus 11.1%, P=0.09).

    Conclusion:

    Current dosing strategies at our hospital appear to put obese patients at higher risk of supratherapeutic VAN troughs and may also increase risks of nephrotoxicity.  Further investigation into improved VAN dosing strategies for our patients is warranted.

    Hana Javaid, MD1, Lisa M. Chirch, MD2 and Jeffrey R. Aeschlimann, Pharm.D.2,3, (1)Infectious Diseases, University of Connecticut Health Center, Farmington, CT, (2)Division of Infectious Diseases, Department of Medicine, University of Connecticut, Farmington, CT, (3)Dept. of Pharmacy Practice, Univ. of Connecticut School of Pharmacy, Farmington, CT

    Disclosures:

    H. Javaid, None

    L. M. Chirch, None

    J. R. Aeschlimann, None

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