OCULAR ABSORPTION OF CYCLOSPORINE-A FROM LIPOSOMES INCORPORATED INTO COLLAGEN SHIELDS

We investigated the ability of liposomes to deliver the immunosuppress ive agent cyclosporine A (CsA) to the cornea, anterior sclera, aqueous humor, and vitreous in rabbit eyes. One drop (10 mu l) of liposome-en capsulated CsA (CsA-LIP) or olive oil drops containing an equivalent c oncentration of CsA (CsA-DR) were administered at 15- minute intervals within the first hour and then one hourly over a 6-hour period. In ad dition, collagen shields soaked for 30 minutes in the liposome prepara tion (CsA-LIP-CS) were tested in vitro and in vivo as a new drug deliv ery approach. CsA levels were measured by fluorescence-immunoassay aft er 1, 3, or 6 hours of drug administration. CsA levels in this study w ere highest in cornea and anterior sclera. In animals receiving either CsA-DR or CsA-LIP, CsA levels generally increased from 1 to 6 hours. In animals receiving a single application of CsA-CS-LIP, CsA levels pe aked at 3 hours and declined at 6 hours in cornea and sclera. CsA-LIP and CsA-CS-LIP delivered significantly higher levels of CsA to the cor nea and sclera at 1 and 3 hours than CsA-DR. In aqueous and vitreous h umor, CsA levels increased from 1 to 6 hours in animals receiving eith er CsA-DR or CsA-LIP. On the other hand, animals receiving a single ap plication of CsA-CS-LIP had lower levels of CsA at 6 hours than at the earlier time points. Animals receiving CsA-LIP or CsA-CS-LIP had sign ificantly higher levels of CsA in aqueous and vitreous humor at 1, 3, and 6 hours than animals receiving CsA-DR. Moreover, animals receiving CsA-CS-LIP had higher CsA levels in aqueous humor at 1 and 3 hours th an animals receiving CsA-LIP, CsA was not detectable in the serum of r abbits in any treatment group. These results demonstrate that liposome -encapsulated CsA is an effective means of intraocular drug delivery. The combination of liposome-encapsulated CsA with collagen shields may offer a new drug device for the eye.