Positively charged microemulsions of dexamethasone: comparative effects of two cosurfactants on ocular drug delivery and bioavailability

Background: The objective of this investigation was to evaluate the potential of mucoadhesive chitosan-coated positively charged microemulsions (CH-MEs) of dexamethasone with respect to the change in nonionic cosurfactants. Methods: CH-MEs were prepared with different concentrations of surfactant and cosurfactant using the water titration method and coated with low-molecular-weight chitosan. Results: All formulations displayed an average globule size between 85 and 187 nm and a positive surface charge. The optimized CH-MEs showed greater penetration of dexamethasone in the anterior segment of the eye, resulting in twofold and fourfold higher dexamethasone concentration than uncoated ME and drug suspension, respectively. Conclusion: The developed CH-MEs shows increases in ocular penetration and bioavailability.