Penetration of cyclosporin A into the rabbit cornea and aqueous humor after topical drop and collagen shield administration.

We used commercially available 12-hour collagen shields to deliver cyclosporin A (CsA) to the cornea and aqueous humor in rabbit eyes. Six New Zealand white rabbits were divided into three groups. The first group (four eyes) received 6 mg of CsA in castor oil and the second group (four eyes) received 6 mg of CsA in olive oil applied as topical drops to rabbit eyes within 12 hours. In the third group (four eyes) 12-hour collagen shields soaked in 6 mg CsA in olive oil were applied to rabbit eyes. The amount of CsA in corneal and aqueous samples from eyes treated with CsA castor oil and CsA olive oil were compared with each other and with collagen shield treated eyes. CsA concentrations were measured by radioimmunoassay. After the total dose of 6 mg CsA, percentage penetration was measured as follows: CsA castor oil--0.51% in aqueous and 20.75% in cornea; CsA olive oil--0.17% in aqueous and 11.13% in cornea; and with collagen shields--0.44% in aqueous and 11.84% in cornea. These results show that the CsA levels of castor oil drops were higher than those obtained with olive oil drops. In eyes with collagen shields, CsA levels were higher than olive oil drops but nearly equal to the castor oil drops. Collagen shields may be useful as an ocular delivery system for CsA.