Abstract
Objective—To determine whether a glomerular filtration rate (GFR) assay based on serum iohexol clearance can be used to predict carboplatin clearance in cats.
Animals—10 cats with tumors.
Procedures—GFR was measured concurrently by use of plasma clearance of technetium Tc 99m–labeled diethylenetriaminepentaacetic acid (99mTc-DTPA) to yield GFR99mTc-DTPA and serum clearance of iohexol to yield GFRIohexol. 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 (AUCTarget) and estimation of platinum clearance (CLPT) derived from GFR99mTc-DTPA as follows: dose = AUCTarget × 2.6 × GFR99mTc-DTPA × body weight, where AUCTarget is 2.75 min·mg·mL−1. Plasma platinum concentrations were measured via atomic absorption spectrophotometry. Values for GFR99mTc-DTPA and GFRIohexol were compared by use of least-squares regression and Bland-Altman analysis. Least-squares regression was used to determine whether CLPT could be predicted from GFR99mTc-DTPA or GFRIohexol (or both).
Results—GFR99mTc-DTPA and GFRIohexol were strongly correlated (r = 0.90), but GFRIohexol values were significantly larger by a factor of approximately 1.4. Platinum clearance had a significant linear relationship to GFR99mTc-DTPA (CLPT = 2.5 × GFR99mTc-DTPA) and to GFRIohexol (CLPT = [1.3 × GFRIohexol] + 1.4).
Conclusions and Clinical Relevance—In cats, serum iohexol clearance was an accurate predictor of CLPT and can be used to calculate the carboplatin dose as follows: dose = AUCTarget × ([1.3 × GFRIohexol] + 1.4) × body weight.
