Kinetics of platinum in cancer patients treated with cisplatin at different doses.
In previous work the authors observed that platinum (free and bound) does not seem to accumulate in the peripheral compartment following the administration of two courses of cisplatin (cis-DDP) therapy (65 mg/m2) in patients with mammary and ovarian cancer. The aim of the present work was to study the disposition of platinum (Pt) after a higher dose of cis-DDP, to verify the rate of free drug penetration into the tissue and to observe changes in protein binding relative to the dose. cis-DDP, at the dose of 100 mg/m2, was administered i.v. over 60 min to patients with lung cancer. Serum and urine were collected before infusion and at various intervals afterwards. The plasma and urine levels of Pt were determined by flameless atomic absorption spectrophotometry, using a Varian model AAS 1475-GTA 95. Serum levels were analysed by a two-compartment open pharmacokinetic model. After the higher dose there was a substantial increase in central volume Pt and slight increase in peripheral volume Pt as compared with levels observed previously at the lower dose. In some subjects receiving high doses elimination half-life decreased and total body clearance increased, while in others these kinetic parameters were unchanged in comparison with those observed after a low dose. Protein binding seems to influence the persistence of platinum in the vascular space, modifying to a minor degree tissue penetration of the drug.