[Tissue levels of locally applied cyclosporin A in the rabbit eye]

Cyclosporin A eye drops (4%) were applied to the conjunctival sac of pigmented rabbits for 4 and 6 weeks. Cyclosporin-A was eluted from biopsy specimens of treated eyes and measured by the commercially available radioimmunoassey. Therapeutic Cyclosporin A levels could be demonstrated with chronic application in the rabbit cornea 3 and 10 h after the last eye drop had been administered suggesting a pooling of the substance in corneal tissue. Other ocular compartments (conjunctiva, iris, lens, vitreous, and aqueous humor) gave results below the therapeutic levels. Immunohistological studies with indirect immunofluorescence demonstrated strong binding to corneal and conjunctival epithelial cell membranes.