title: Evaluation of iohexol clearance used to estimate glomerular filtration rate in clinically normal foals.
abstract: OBJECTIVE
  To determine whether pharmacokinetic analysis of data derived from a single i.v. dose of iohexol could be used to predict creatinine clearance and evaluate simplified methods for predicting serum clearance of iohexol with data derived from 2 or 3 blood samples in clinically normal foals.
  
  
  METHODS
  10 healthy foals.
  
  
  METHODS
  Serum disposition of iohexol and exogenous creatinine clearance was determined simultaneously in each foal (5 males and 5 females). A 3-compartment model of iohexol serum disposition was selected via standard methods. Iohexol clearance calculated from the model was compared with creatinine clearance. Separate limited-sample models were created with various combinations of sample times from the terminal slope of the plasma versus time profile for iohexol. Correction factors were determined for the limited-sample models, and iohexol clearance calculated via each method was compared with exogenous creatinine clearance by use of method comparison techniques.
  
  
  RESULTS
  Mean exogenous creatinine clearance was 2.17 mL/min/kg. The disposition of iohexol was best described by a 3-compartment open model. Mean clearance value for iohexol was 2.15 mL/min/kg and was not significantly different from mean creatinine clearance. A method for predicting serum iohexol clearance based on a 2-sample protocol (3- and 4-hour samples) was developed.
  
  
  CONCLUSIONS
  Iohexol clearance can be used to predict exogenous creatinine clearance and can be determined from 2 blood samples taken after i.v. injection of iohexol. Appropriate correction factors for adult horses and horses with abnormal glomerular filtration rate need to be determined.
authors.affiliation: Department of Large Animal Clinical Science, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, VA 24060, USA.
authors.forename: Kathleen C
authors.initials: KC
authors.lastname: Gonda
authors.forename: Jeff R
authors.initials: JR
authors.lastname: Wilcke
authors.forename: Mark V
authors.initials: MV
authors.lastname: Crisman
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Ward
authors.forename: John L
authors.initials: JL
authors.lastname: Robertson
authors.forename: Delmar R
authors.initials: DR
authors.lastname: Finco
authors.forename: W Emmett
authors.initials: WE
authors.lastname: Braselton
mesh_terms: D000818:Animals; D003287:Contrast Media / Q000493:pharmacokinetics*; D003404:Creatinine / Q000097:blood / Q000378:metabolism; D005919:Glomerular Filtration Rate / Q000502:physiology* / Q000662:veterinary*; D006736:Horses / Q000502:physiology*; D007472:Iohexol / Q000493:pharmacokinetics*
chemical_list: D003287:Contrast Media; D007472:Iohexol; D003404:Creatinine