Carboplatin and cisplatin pharmacokinetics after intrapleural combination treatment in patients with malignant pleural effusion

Background. Cisplatin (DDP) and carboplatin (CBDCA) are two of the most effective drugs in a locoregional approach. Since simultaneous combined treatment with intrapleural DDP and CBDCA has not been reported in humans; we investigated its use in patients with malignant effusions, focusing on pharmacokinetics. Patients and methods. The pharmacokinetics of DDP and CBDCA were studied in 10 patients with malignant pleural effusion treated intrapleurally with a combination of DDP (60 mg/m(2)) and CBDCA (270 mg/m(2)) and in additional patients who received the same doses of drugs administered intravenously as single agents or in combination. Platinum (Pt) species originating from DDP (metabolites plus unchanged DDP) and intact CBDCA in plasma and pleural fluid ultra-filtrates were measured by means of high performance liquid chromatography and atomic absorption spectrometry. Results: Both in the plasma and pleural fluid, the total levels of free Pt represented the additive result of the individual concentrations of CBDCA and Pt-species derived from DDP. After intrapleural combination, high pleural-plasma ratios of the peak concentrations and AUCs were observed both for CBDCA and DDP-derived Pt species, highlighting a distinct local pharmacological advantage. However, the Pt species originating from DDP were absorbed more rapidly from the pleural cavity than CBDCA (K-a = 86 x 10(-3) vs. 37 x 10(-3) min(-1), P < 0.05). Intrapleural combination of CBDCA and DDP produced therapeutic plasma levels of reactive (free) DDP species and increased the extent of their residence time (MRT) compared with single intravenous DDP treatment [peak concentration: 1.1 +/- 0.1 (SD) vs. 1.6 +/- 0.2 mu g/ml; MRT: 5.2 +/- 1.9 vs. 0.5 +/- 0.06 h]. Furthermore, the plasma AUC of free CBDCA after intrapleural combined treatment (2.1 +/- 0.5 mg/ml x min) was similar to that after intravenous administration of CBDCA alone (2.1 +/- 0.2 mg/ml x min). The intrapleural treatment was well tolerated by all patients. Toxicity consisted of mild nausea and vomiting (grade 1-2 according to the WHO scale) in four patients. Myelosuppression (grade 1-2) was remarkable only in two heavily pretreated patients. No evidence of recurrence of the pleural effusion was observed in six patients (complete response), while an asymptomatic minimal fluid reaccumulation not requiring drainage (partial response) was observed in four patients. Conclusions. The pharmacologic results seem to exclude a pharmacokinetic interaction between CBDCA and DDP and suggest that a dose of CBDCA 2-fold higher than that used in this study associated intrapleurally with 60 mg/m(2) DDP could induce an acceptable and predictable myelosuppression.