Purpose: Carboplatin dose is calculated based on kidney function, commonly estimated with imperfect creatinine-based formulae. Iohexol is used to measure glomerular filtration rate (GFR) and allows calculation of a more appropriate carboplatin dose. To address potential concerns that iohexol administered during a course of chemotherapy impacts that therapy, we performed in vitro and in vivo pharmacokinetic drug-drug interaction evaluations of iohexol.Methods: Carboplatin was administered IV to female mice at 60 mg/kg with or without iohexol at 300 mg/kg. Plasma ultrafiltrate, kidney and bone marrow platinum was quantitated by atomic absorption spectrophotometry. Paclitaxel microsomal and gemcitabine cytosolic metabolism as well as metabolism of CYP and UGT probes was assessed with and without iohexol at 300 μg/mL by LC-MS/MS.
Results:In vivo carboplatin exposure was not significantly affected by iohexol co-administration (platinum AUC combination vs alone: plasma ultrafiltrate 1,791 vs 1,920 μg/mL•min; kidney 8,367 vs 9,757 μg/g•min; bone marrow 12.7 vs 12.7 μg/mg-protein•min). Paclitaxel microsomal metabolism was not impacted (combination vs alone: 6-α-OH-paclitaxel 38.3 versus 39.4 ng/mL/ 60min; 3-p-OH-paclitaxel 26.2 versus 27.7 ng/mL/60min). Gemcitabine human cytosolic elimination was not impacted (AUC combination vs gemcitabine alone: dFdU 24.1 versus 23.7