Evaluation of serum iohexol clearance for use in predicting carboplatin clearance in cats.
OBJECTIVE
To determine whether a glomerular filtration rate (GFR) assay based on serum iohexol clearance can be used to predict carboplatin clearance in cats.


METHODS
10 cats with tumors.


METHODS
GFR was measured concurrently by use of plasma clearance of technetium Tc 99m-labeled diethylenetriaminepentaacetic acid ((99m)Tc-DTPA) to yield GFR(99mTc-DTPA) and serum clearance of iohexol to yield GFR(Iohexol). A single dose of carboplatin was administered IV as a bolus. Dose was calculated by use of a target value for the area under the plasma platinum concentration-versus-time curve (AUC(Target)) and estimation of platinum clearance (CL(PT)) derived from GFR(99mTc-DTPA) as follows: dose = AUC(Target) x 2.6 x GFR(99mTc-DTPA) x body weight, where AUC(Target) is 2.75 min.mg.mL(-1). Plasma platinum concentrations were measured via atomic absorption spectrophotometry. Values for GFR(99mTc-DTPA) and GFR(Iohexol) were compared by use of least-squares regression and Bland-Altman analysis. Least-squares regression was used to determine whether CL(PT) could be predicted from GFR(99mTc-DTPA) or GFR(Iohexol) (or both).


RESULTS
GFR(99mTc-DTPA) and GFR(Iohexol) were strongly correlated (r = 0.90), but GFR(Iohexol) values were significantly larger by a factor of approximately 1.4. Platinum clearance had a significant linear relationship to GFR(99mTc-DTPA) (CL(PT) = 2.5 x GFR(99mTc-DTPA)) and to GFR(Iohexol) (CL(PT) = [1.3 x GFR(Iohexol)] + 1.4).


CONCLUSIONS
In cats, serum iohexol clearance was an accurate predictor of CL(PT) and can be used to calculate the carboplatin dose as follows: dose = AUC(Target) x ([1.3 x GFR(Iohexol)] + 1.4) x body weight.
Bailey
Dennis B
DB
Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Rassnick
Kenneth M
KM
Prey
Joshua D
JD
Dykes
Nathan L
NL
D000818:Animals; D019540:Area Under Curve; D001830:Body Surface Area; D001835:Body Weight; D016190:Carboplatin / Q000097:blood / Q000378:metabolism*; D002277:Carcinoma / Q000188:drug therapy / Q000503:physiopathology / Q000662:veterinary; D002371:Cat Diseases / Q000188:drug therapy / Q000503:physiopathology; D002415:Cats / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D005919:Glomerular Filtration Rate / Q000502:physiology*; D007472:Iohexol / Q000378:metabolism*; D008657:Metabolic Clearance Rate; D012509:Sarcoma / Q000188:drug therapy / Q000503:physiopathology / Q000662:veterinary; D016284:Technetium Tc 99m Pentetate / Q000493:pharmacokinetics
D007472:Iohexol; D016190:Carboplatin; D016284:Technetium Tc 99m Pentetate