Formulation of an ophthalmic lipid emulsion containing an anti-inflammatory steroidal drug, difluprednate

Preparation of oil-in-water (o/w) type lipid emulsion is one of the approaches to formulate drugs that are poorly water-soluble but can be dissolved in the oil phase of the emulsions. A synthetic glucocorticoid medicine, difluprednate (DFBA), is a water-insoluble compound. We formulated DFBA (0.05%, w/v) ophthalmic lipid emulsion containing 5.0% (w/v) caster oil and 4.0% (w/v) polysorbate 80. The appearance of the emulsion was blue and translucent lipid emulsion, and the median particle size of the lipid emulsion was 104.4 nm. Neither separation nor change in particle size was observed after 6 months at 40 °C. Furthermore, when compared with DFBA (0.05%, w/v) ophthalmic suspension, the lipid emulsion showed 5.7-fold higher concentration of DFB that was an active metabolite of DFBA in aqueous humor at 1 h after instillation. Ophthalmic lipid emulsion enhances the intraocular penetration of drugs, and it is useful as a delivery system for the ophthalmic preparations of lipophilic drugs.