Oxaliplatin is a novel platinum complex used for the treatment of metastatic colorectal carcinoma. The pharmacokinetics of the free fraction of oxaliplatin in blood were evaluated in 10 patients given 85 mg/m2 of oxaliplatin using an infusion time of 2 h. Blood samples were collected during and after the infusion and immediately placed on ice. The samples were ultrafiltrated centripetally and the concentration of oxaliplatin in the ultrafiltrate was determined by liquid chromatography in combination with postcolumn derivatization. The in vitro degradation rate was determined in blood from the patients taken immediately before drug administration. The maximal blood concentration (C(max)) and terminal half-life (t1/2) were 1.44 +/- 0.20 (SD) microg/mL and 14.1 min (range: 10.2-24.5), respectively. The area under the blood concentration time curve (AUC), clearance (CL), and distribution volume (V(ss)) were (means +/- SD) 161 +/- 22 microg min/mL, 32.1 +/- 4.2 L/h/m2, and 0.26 +/- 0.06 L/kg, respectively. There was a significant correlation between the clearance of oxaliplatin in the patients and the degradation rate in whole blood (r = 0.746; p = 0.017). Oxaliplatin has a short elimination half-life, which is in a sharp contrast to previously reported elimination half-lives obtained by analysis of the platinum content in plasma and ultrafiltrate. The correlation between in vivo and in vitro data suggests that the degradation in whole blood plays a role for the elimination of the drug.