Evaluation of iohexol clearance used to estimate glomerular filtration rate in clinically normal foals.
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.
Gonda
Kathleen C
KC
Department of Large Animal Clinical Science, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, VA 24060, USA.
Wilcke
Jeff R
JR
Crisman
Mark V
MV
Ward
Daniel L
DL
Robertson
John L
JL
Finco
Delmar R
DR
Braselton
W Emmett
WE
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*
D003287:Contrast Media; D007472:Iohexol; D003404:Creatinine