Acta Pharmacologica Sinica 2006 June; 27 (6): 747-753; doi: 10.1111/j.1745-7254.2006.00340.x

Aim: To investigate the preparation, in vitro release, in vivo pharmacokinetics and tissue distribution of a novel polymeric micellar formulation of paclitaxel (PTX) with Pluronic P123.

Methods: The polymeric micelles of paclitaxel with Pluronic P123 were prepared by a solid dispersion method. The characteristics of micelles including particle size distribution, morphology and in vitro release of PTX from micelles were carried out. PTX-loaded micellar solutions were administered through the tail vein to healthy Sprague-Dawley rats and Kunming strain mice to assess the pharmacokinetics and tissue distribution of PTX, respectively. Taxol, the commercially available intravenous formulation of PTX, was also administered as control.

Results: By using a dynamic light scattering sizer and a transmission electron microscopy, it was shown that the PTX-loaded micelles had a mean size of approximately 25 nm with narrow size distribution and a spherical shape. PTX was continuously released from Pluronic P123 micelles in release medium containing 1 mol/L sodium salicylate for 24 h at 37 °C. In the pharmacokinetic assessment, t_1/2b and AUC of micelle formulation were 2.3 and 2.9-fold higher than that of Taxol injection. And the PTX-loaded micelles increased the uptake of PTX in the plasma, ovary and uterus, lung, and kidney, but decreased uptake in the liver and brain in the biodistribution study.

Conclusion: Polymeric micelles using Pluronic P123 can effectively solubilize PTX, prolong blood circulation time and modify the biodistribution of PTX.

Keywords: paclitaxel; micelle; Pluronic P123; pharma-cokinetics; biodistribution