Disposition kinetics of taxanes after intraperitoneal administration in rats and influence of surfactant vehicles.

Rats were intraperitoneally administered 40 mg x kg(-1) of paclitaxel or docetaxel dissolved in various drug solutions. The drug solutions were prepared using 20 mL of saline, adding 4.2% Cremophor EL (crEL) for paclitaxel (TXL), and 1.5% Polysorbate-80 (PS-80) (TXT), 7.5% PS-80 (TXT+PS-80) or 4.2% crEL (TXT+crEL) for docetaxel. The apparent first-order absorption rate constant from the peritoneal cavity (k(a)) of TXL was about one-twentieth of that of TXT. The ratio of the area under the concentration-time curve of drug in plasma over that in ascites for TXL was about one-third of that of TXT. The values of the above ratio and the k(a) of TXT+PS-80 and TXT+crEL were similar to those of TXL. After intraperitoneal administration, the values of the blood-to-plasma concentration ratio in the four groups were similar and independent of time. In the in-vitro study, PS-80 and crEL caused similar, concentration-dependent decreases of drug permeation into red blood cells after a 15-min incubation of rat blood with 10 microg x mL(-1) of TXL. We demonstrated that the disposition kinetics of taxanes after intraperitoneal administration to rats was strongly influenced, in a concentration-dependent manner, by the surfactant vehicle used, crEL or PS-80.