Comparative effects of different cosurfactants on sterile prednisolone acetate ocular submicron emulsions stability and release.

Pluronic F68 is a nonionic, thermogelling block copolymer showing a high dehydration resistance during autoclaving due to its high cloud point (>100 degrees C). Tween 80 (with cloud point of 72.5 degrees C), is a polyoxyethylene-based cosurfactant, susceptible to temperature because of a decrease in its solubility by temperature increase. This study was done to explore whether or not, when compared with Tween 80, Pluronic F68 could be used blindly as a suitable cosurfactant for the preparation of terminally sterilized ocular submicron emulsions containing a lipid soluble drug, prednisolone acetate (PA). Various oils of variable viscosities were also tried. The results proved that no prediction can be made based on previously known physico-chemical properties alone and that emulsion stability depends on the contribution of the various emulsion components including: oil, surfactant and cosurfactant, in addition to the drug properties.