Hydrotropic agents for study of in vitro paclitaxel release from polymeric micelles

A new experimental method for in vitro release studies of poorly soluble drugs from polymeric micelle systems was developed using a hydrotropic agent, sodium salicylate. It is difficult to maintain a good sink condition for poorly water-soluble drugs, such as paclitaxel (PTX), because of their low aqueous solubility. In this study, a good sink condition for PTX was achieved by using aqueous sodium salicylate solution which solubilized more than 10 times the total amount of PTX incorporated in polymeric micelles. Sodium salicylate at 1 M concentration increased the aqueous PTX solubility by 100 times without destroying the micellar structure of poly(ethylene glycol)-block-poly(phenylalanine) (PEG-b-PPhe) copolymer. PTX was continuously released from PEG-b-PPhe micelles in the hydrotropic release medium. The hydrotropic solution presents a simple method for studying in vitro release behavior of poorly soluble drugs from polymeric micelles in aqueous media.