Pharmacokinetics of oxaliplatin in patients with normal versus impaired renal function

The pharmacokinetics (PK) of platinum was investigated and compared in patients with normal (NRF) and impaired renal function (IRF), after they had received oxaliplatin at the recommended dose and delivery modality.

Oxaliplatin was administered at 130 mg/m(2) as a 2-h infusion without hydration. Patients were recruited and classified according to their creatinine clearance (CrCl > or < 60 ml/min), calculated using the Cockcroft and Gault formula. Blood was taken for PK analysis during and after the infusion. Twenty-three patients were included in the PK analysis (13 NRF and 10 IRF). At inclusion, the median CrCls were 70.5 ml/min (range 63-136) for the NRF group and 42 ml/min (range 27-57) for the IRF group. Three patients underwent a second course of treatment and additional blood sampling for analysis. Platinum levels in the plasma, ultrafiltrate and red blood cells (RBCs) were measured using flameless atomic absorption spectrophotometry (FAAS).

Following the administration of oxaliplatin, platinum binding to plasma proteins and RBCs was rapid and extensive; at the end of the 2-h infusion, 27% of the platinum in the plasma remained free (40% bound to RBCs, 33% bound to plasma proteins). Neither the mean maximal concentration (C(max)) of total platinum in the plasma, the mean C(max) of ultrafilterable platinum in the plasma, nor the maximal platinum content in the RBCs differed significantly between the two groups (2.59 vs 2.58 microg/ml, 1.09 vs 1.28 microg/ml and 2. 06 vs 2.17 microg/ml, respectively, for patients with NRF vs IRF). After the end of the infusion, levels of total and free (ultrafilterable) platinum in the plasma declined biexponentially. The plasma clearance of both total and free platinum as well as the area under the curve (AUC) of the free platinum fraction correlate with the calculated CrCl (P=9 x 10(-3), P=3.1 x 10(-5) and P=9 x 10(-6), respectively). After a single course of oxaliplatin, toxicities reported in the two groups of patients were similar.

Our results are in agreement with the in vitro data concerning the extensive binding of oxaliplatin to plasma proteins and RBCs. They also reveal a strong negative correlation between free drug plasma availability and renal function, with a corresponding positive correlation between clearance of the plasmatic platinum and renal function. Thus, renal impairment entails a greater overall exposure to platinum in the plasma. However, this study failed to elicit any relationship between moderate renal impairment and the acute toxicity associated with oxaliplatin.