Abstract
Purpose:
Microemulsions provide an attractive means of delivering certain therapeutic molecules to the posterior segment via topical administration. We aim to develop a library of microemulsions from which hydrophobic drugs can be screened and compatible formulations identified.
Methods:
A microemulsion is a system of water, oil and surfactant. It is a single optically isotropic and thermodynamically stable, self-assembled liquid solution. Surfactants and other excipients were selected from the USFDA inactive ingredient database for all formulations. Combinations of the water, oil and surfactant were systematically evaluated for the formation of microemulsions. The resulting formulations were topically applied bilaterally in a volume of 10 µl, 4 times/day to C57Bl/6 mice for a total of 5 days. They were scored once a day for hyperemia, chemosis and discharge.
Results:
To date, >20,000 emulsions have been formulated, from which we have identified 500 microemulsions, and 47 microemulsions were chosen randomly and evaluated for ocular tolerability. Twenty-three of the formulations showed no hyperemia, chemosis or discharge over the 5 days of QID dosing.
Conclusions:
Approximately 50% of the formulations were shown to be well tolerated in this acute study. Current studies to quantify the capability of these microemulsions to deliver various therapeutic molecules to the posterior segment will yield valuable insight towards the development of new topical formulations. Since interactions are unique to the molecule and unpredictable, a large data base is needed because the very presence of the drug can destabilize the emulsion. These results have formed the basis for our formulation screening platform in which we intend to further expand our library to include more oil and surfactants.
Keywords: 607 nanotechnology •
608 nanomedicine •
688 retina