Carbopol/pluronic phase change solutions for ophthalmic drug delivery

The major purpose of this study is to develop and characterize a series of carbopol- and pluronic-based solutions as the in situ gelling vehicles for ophthalmic drug delivery. The rheological properties, in vitro release as well as in vivo pharmacological response of various polymer solutions, including carbopol, pluronic and carbopol/pluronic solution, were evaluated. It was found that the optimum concentration of carbopol solution for the in situ gel forming delivery systems was 0.3% (w/w), and that for plutonic solution was 14% (w/w). The mixture of 0.3% carbopol and 14% pluronic solutions showed a significant enhancement in gel strength in the physiological condition; this gel mixture was also found to be free flowing at pH 4.0 and 25 degreesC. The rheological behaviors of carbopol/pluronic solution were not affected by the incorporation of pilocarpine hydrochloride. Both the in vitro release and in vivo pharmacological studies indicated that the carbopol/ pluronic solution had the better ability to retain drug than the carbopol or pluronic solutions alone. The results demonstrated that the carbopol/pluronic mixture can be used as an in situ gelling vehicle to enhance the ocular bioavailability. (C) 2000 Elsevier Science B.V. All rights reserved.