[Pharmacokinetics of cisplatin and the effect of sodium thiosulfate]

The pharmacokinetics of cisplatin (cis-dichlorodiammineplatinum (II), CDDP) have been studied in 11 patients. Plasma and urine CDDP concentrations were determined by flameless atomic absorption spectrophotometry. The treatment schedule was administered either by a 3-hour and 4-hour i.v. infusion or a 1.5-hour i.a. infusion. In the 3-hour i.v. infusion, the peak level of plasma total CDDP was 4.09 micrograms/ml after the end of infusion and non-protein-bound CDDP was 0.78 microgram/ml. Plasma total CDDP level declined with two peaks, the half-life of the alpha phase being 3.3 hours and that of the beta phase being 5.29 days. The half-life of non-protein-bound CDDP was 1.6 hours. CDDP might have remained for a long time, because CDDP values were obtained 3 weeks after infusion and urinary recovery of CDDP showed low values. Its urinary recovery was 40.3% of the dose infusion in the first 24 hours and 48.0% in 96 hours. The protein-binding of CDDP was inhibited by sodium thiosulfate(STS) and renal urinary excretion was enhanced. Our data suggest that STS can be applied as a neutralizer of CDDP.