Selective Tissue Penetration of the Corneal Layers of Cyclosporin 2% Associated with Miglyol in Rabbits

Purpose: Cyclosporin A (CsA) is a drug used to prevent immune rejection in corneal transplantation. Most grafts performed today are endothelial grafts which are complicated with poor penetration of CsA into the endothelium due to its hydrophobicity. To improve CsA penetration into the corneal a new ocular formulation of CsA 2% with Miglyol was developed and is commercially available. The purpose of this pharmacokinetic study was to determine the concentrations of CsA in all layers of the cornea, in particular in the endothelium after topical administration of CsA 2%-Miglyol in rabbits. Methods: Sixteen rabbits were divided in 4 groups according to the time from the last instillation of CsA 2%-Miglyol to corneal sampling. Rabbit eyes received one drop of CsA twice a day for 5 days. Corneal tissue and plasma samples were collected at 2, 6, 12, and 24 h. CsA concentrations were measured using liquid chromatography-tandem mass spectrometry method. Results: Maximum concentrations (Cmax) of CsA were obtained in corneal tissues within 2 h after the last instillation of CsA 2%-Miglyol, except in the endothelium (12 h). Cmax were 59.75 ± 12.09 ng/mg, 15.66 ± 4.31 ng/mg, 5.17 ± 0.88 ng/mg, and 2.65 ± 0.47 ng/mg for the epithelium, endothelium, anterior stroma and posterior stroma. CsA concentrations remained high over a 24-h in all corneal layers. Conclusions: The topical application of CsA 2%-Miglyol allowed a high concentration of CsA in the corneal endothelium. The good penetration of CsA into the endothelium suggests that this formulation can be effective to prevent endothelial graft rejection.