Corneal permeation studies of everolimus microemulsion

Purpose: To prevent corneal-graft rejection, the topical application of an immunosuppressive drug is an alternative to the systemic application of immunosuppressive drugs or corticosteroids, which may have adverse side effects. The aim of this study was to determine the permeation rate of everolimus through freshly isolated pig cornea (ex vivo). Methods: A fluorescence polarization immunoassay with a commercially available assay system was used to quantify everolimus in the acceptor samples of the permeation tests. Results: Everolimus is a poorly soluble drug and was, therefore, incorporated in an eye-administrable microemulsion. The stability of this microemulsion containing 0.1% (1 mg/mL) of the drug was satisfying over a period of 12 months. A concentration of 8.64 ng/mL was already reached 30 min after administration of the microemulsion to the cornea. Conclusions: This everolimus-containing microemulsion is a promising ocular formulation for preventing corneal-graft rejection.