title: Evaluation of a New Vancomycin Dosing Protocol in Morbidly Obese Patients.
abstract: BACKGROUND
  Optimal dosing of vancomycin in morbidly obese patients (>100 kg and at least 140% of their ideal body weight) has not been determined. Conventional dosing strategies have led to the observation of supratherapeutic trough concentrations (>20 mcg/mL).
  
  
  OBJECTIVE
  To evaluate the effectiveness of a new vancomycin dosing protocol in morbidly obese patients in achieving therapeutic trough concentrations between 10 and 20 mcg/mL and to determine patient-specific factors influencing the trough concentration attained.
  
  
  METHODS
  A single-center, retrospective chart review included morbidly obese adult patients with a pharmacy-to-dose vancomycin consult and at least 1 trough concentration obtained at steady state. Patients were excluded if they had a creatinine clearance (CrCl) less than 35 mL/min or unstable renal function, were not dosed according to the revised protocol, or received vancomycin prior to initiation of the protocol.
  
  
  RESULTS
  Of the 48 patients included, 17 (35.4%) achieved a therapeutic vancomycin trough concentration. Subtherapeutic concentrations (<10 mcg/mL) were observed in 27 patients (56.3%) and supratherapeutic concentrations were observed in 4 (8.3%) patients. Age less than 45 years and CrCl greater than 100 mL/min were associated with subtherapeutic trough concentrations.
  
  
  CONCLUSIONS
  This study demonstrates that the revised vancomycin dosing protocol led to the attainment of therapeutic trough concentrations in 35.4% of patients. The majority had subtherapeutic concentrations, which increases the risk of treatment failures and resistance. Further study is needed to determine the optimal dosing strategy in this patient population.
authors.affiliation: Critical Care Pharmacy Specialist, Carolinas Healthcare System , Charlotte, North Carolina.
authors.forename: Desiree E
authors.initials: DE
authors.lastname: Kosmisky
authors.affiliation: Medical ICU Clinical Pharmacy Specialist, Carolinas Medical Center, Charlotte, North Carolina; Assistant Professor of Pharmacy, Wingate University School of Pharmacy, Wingate, North Carolina.
authors.forename: Carrie L
authors.initials: CL
authors.lastname: Griffiths
authors.affiliation: Statistician, Dickson Advanced Analytics Group, Carolinas Healthcare System , Charlotte, North Carolina.
authors.forename: Megan A
authors.initials: MA
authors.lastname: Templin
authors.affiliation: Director of Biostatistics, Carolinas Healthcare System, Charlotte , North Carolina.
authors.forename: James
authors.initials: J
authors.lastname: Norton
authors.affiliation: Infectious Diseases and Antimicrobial Stewardship Clinical Pharmacy Specialist, Carolinas Medical Center, Charlotte , North Carolina .
authors.forename: Kelly E
authors.initials: KE
authors.lastname: Martin
keywords: dosing; obesity; therapeutic drug monitoring; vancomycin