title: Plasma Peak and Trough Gentamicin Concentrations in Hospitalized Horses Receiving Intravenously Administered Gentamicin.
abstract: BACKGROUND
  Gentamicin is an aminoglycoside antimicrobial commonly used in horses at 6.6 mg/kg IV once daily. Therapeutic drug monitoring (TDM) can confirm desired peak concentration is reached for common bacterial isolates, and detect toxicosis associated with high trough values.
  
  
  OBJECTIVE
  Determine the relationship between gentamicin dose and plasma concentration in hospitalized horses, and identify a starting dose range to achieve peaks > 32 μg/mL.
  
  
  METHODS
  Sixty-five horses (2002-2010) receiving once-daily gentamicin with TDM performed (N = 99 sets).
  
  
  METHODS
  Retrospective study. Data from hospitalized horses including weight, dose, plasma peak, and trough gentamicin concentration, creatinine concentrations and presence of focal or systemic disease were collected from medical records. Peak concentrations measured 25-35 minutes after administration were included (N = 77). Data were divided into low (<7.7 mg/kg), medium (7.7-9.7 mg/kg) and high (>9.7 mg/kg) dose groups, and were grouped by the horse having focal or systemic disease.
  
  
  RESULTS
  Peak concentrations resulting from doses ≥7.7 mg/kg were 5.74 μg/mL (SE 2.1 μg/mL) greater than peaks from doses <7.7 mg/kg (P = .007). Peak concentrations was 3.6 times more likely to be >32 μg/mL if dose was ≥7.7 mg/kg (P = .04). There were no significant effects of dose on trough or creatinine concentration. At a given dose, horses with focal disease had higher peaks than those with systemic disease (P = .039).
  
  
  CONCLUSIONS
  These data suggest gentamicin dosage should be individually determined in horses using TDM, but support an initial once-daily dose of 7.7-9.7 mg/kg IV to achieve peaks >32 μg/mL and trough concentrations <2 μg/mL. Further studies evaluating the safety of doses >6.6 mg/kg are required.
authors.affiliation: Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA.
authors.forename: J R
authors.initials: JR
authors.lastname: Bauquier
authors.affiliation: Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA.
authors.forename: R C
authors.initials: RC
authors.lastname: Boston
authors.affiliation: Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA.
authors.forename: R W
authors.initials: RW
authors.lastname: Sweeney
authors.affiliation: Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA.
authors.forename: P A
authors.initials: PA
authors.lastname: Wilkins
authors.affiliation: Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA.
authors.forename: R D
authors.initials: RD
authors.lastname: Nolen-Walston
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000627:therapeutic use*; D005260:Female; D005839:Gentamicins / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000627:therapeutic use*; D006734:Horse Diseases / Q000097:blood / Q000188:drug therapy*; D006736:Horses; D006762:Hospitals, Animal; D008297:Male; D012189:Retrospective Studies
chemical_list: D000900:Anti-Bacterial Agents; D005839:Gentamicins
keywords: Aminoglycoside; Equine; Pharmacokinetics; Therapeutic drug monitoring