Aim:To investigate the preparation,in vitro release,in vivo pharmacokineticsand tissue distribution of a novel polymeric micellar formulation of paclitaxel(PTX)with Pluronic P123.Methods:The polymeric micelles of paclitaxel with PluronicP123 were prepared by a solid dispersion method.The characteristics of micellesincluding particle size distribution,morphology and in vitro release of PTX frommicelles were carried out.FFX-loaded micellar solutions were administered throughthe tail vein to healthy Sprague-Dawley rats and Kunming strain mice to assessthe pharmacokinetics and tissue distribution of PTX,respectively.Taxol,thecommercially available intravenous formulation of PTX,was also administered ascontrol.Results:By using a dynamic light scattering sizer and a transmissionelectron microscopy,it was shown that the PTX-loaded micelles had a mean sizeof approximately 25 nm with narrow size distribution and a spherical shape.PTXwas continuously released from Pluronic P 123 micelles in release medium contain-ing 1 mol/L sodium salicylate for 24 h at 37℃.In the pharmacokinetic assessment,t_(1/2β)and AUC of micelle formulation were 2.3 and 2.9-fold higher than that of Taxolinjection.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 inthe biodistribution study.Conclusion:Polymeric micelles using Pluronic P123can effectively solubilize PTX,prolong blood circulation time and modify thebiodistribution of PTX. 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. of micellesincluding particle size distribution, morphology and in vitro release of PTX frommicelles were carried out. FFX-loaded micellar solutions were administered through the tail vein to healthy Sprague-Dawley rats and Kunming strain mice to assessthe pharmacokinetics and tissue distribution of PTX, respectively. Taxol , the commercially available available 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 P 123 micelles in rele ase medium contain 1 mol / L sodium salicylate for 24 h at 37 ° C. In the pharmacokinetic assessment, t 1/2 (1/2 β) and AUC of micelle formulation were 2.3 and 2.9-fold higher than that of Taxolinjection. 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 inthe biodistribution study. Conlusion: Polymeric micelles using Pluronic P123can effectively solubilize PTX, prolong blood circulation time and modify thebiodistribution of PTX.