Clinical pharmacokinetics and metabolism of paclitaxel after polychemotherapy with the cytoprotective agent amifostine.

BACKGROUND: Cytoprotection of healthy cells represents a new approach in cancer chemotherapy, but a pharmacokinetic drug interaction between the cytostatic and the cytoprotectant is undesired. METHODS: The purpose was to evaluate the clinical pharmacokinetics (PHK) of paclitaxel (PACLI) and its metabolites under cytoprotection in patients suffering from breast cancer. PACLI was administered alone and in a second cycle in combination with amifostine (AMI) as a paired cross over. RESULTS: In both treatment schedules the steady state of PACLI occurred after 3 hours, the tmax of metabolites between 3 and 4 hours. The mean steady-state concentration was cmax = 5432 +/- 1238 ng/ml in the control group and cmax = 5140 +/- 2407 ng/ml in the AMI group. For the serum metabolites, the findings were very similar: 6-OH-PACLI: cmax 413 +/- 153 ng/ml versus 432 +/- 304 ng/ml, 3"-OH-PACLI: cmax 99 +/- 103 ng/ml versus 123 +/- 98 ng/ml, 3",6-DiOH-PACLI: cmax 43 +/- 55 ng/ml versus 75 +/- 85 ng/ml. AUC values of metabolites were slightly higher in the AMI group, but PHK seemed equal. CONCLUSION: The results gave evidence, that cytoprotection with AMI has no clinical consequences on PACLI pharmacokinetics and biotransformation.

Long-term pharmacokinetics of doxorubicin HCl stealth liposomes in patients after polychemotherapy with vinorelbine, cyclophosphamide and prednisone (CCVP).

The concentration-time profiles of Doxorubicin (DOXO) from day 0 to day 21 after i.v. infusion of 25 or 30 mg/m2 doxorubicin HCI stealth liposomes (Caelyx) were investigated in 9 patients receiving combination polychemotherapy with cyclophosphamide, vinorelbine and prednisone. Peak serum concentrations occurred from 0.04 to 4.0 days after infusion (mean tmax = 1.79 +/- 1.55 d) with a mean cmax of 4,595 +/- 2,849 ng/ml. A total amount of 12.84 +/- 2.47 mg liposomal DOXO in the plasma volume (Vp = 2,794 + 537 ml) could be estimated at tmax (= 27 % of the mean dose of 47.6 mg). Stealth liposomes were eliminated slowly from the blood with a mean t 1/2el of 1.9 + 0.5 days (MRT was 4.6 + 2.5 days). AUClast values ranged from 8,070 to 33,446 ng/ml*d (mean 10,987 +/- 9,339 ng/ml*d). The low plasma clearance (Cltot = 4,681 +/- 2,835 ml/day) and the small volume of distribution (Vz = 11.7 +/- 6.31) suggested that stealth-liposomes were stable in the blood at least for 14 days. Polychemotherapy with Hyper-CCVP schedule did not alter the stability of stealth liposomes, but peak levels of DOXO seemed to be somewhat lower compared to regression analysis of literature data (cmax versus dosage range from 20 to 60 mg/m2). Due to clast occurring between day 12 to 18, no indices for an accumulation of the drug in the blood could be found, when liposomes were given every four weeks.