Determination of permeability coefficients of ophthalmic drugs through different layers of porcine, rabbit and bovine eyes

Comparison of permeability coefficients of lidocaine, ciprofloxacin, timolol and dexamethasone for the cornea and a multi-layer complex of porcine, bovine and rabbit eyes To treat ophthalmic diseases like glaucoma or inflammatory disorders topically applied ophthalmic formulations such as eye drops are usually used. In addition, novel ophthalmic implants releasing drug substances locally into different parts of the eye are available today. In the work presented here, the permeability coefficients of selected drugs (ciprofloxacin hydrochloride, lidocaine hydrochloride, timolol maleate) for ophthalmic tissues were determined using side-by-side diffusion chambers (so-called Ussing chambers). Sclera, conjunctiva, cornea, choroidea–retina-complex and a complex of conjunctiva–sclera–choroidea–retina were excised from fresh porcine, rabbit and bovine eyes. In the porcine eye tissues the highest Papp values were obtained for conjunctiva with the exception of lidocaine. Therefore, it can be estimated that a certain amount of drug diffuses or is transported through conjunctiva after application. The Papp values for sclera were also higher than those for cornea and even more, the surface area of sclera which is available for drug absorption is much larger than that of cornea when applying an implant. The obtained permeability coefficients for sclera and conjunctiva indicate that the administration of periocular implants can be an alternative to topically applied formulations. The complexes of the tissues were a significantly (p