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Sung Jin Lee, Esther S. Kim, Dayle H. Geroski, Bernard E. McCarey, Henry F. Edelhauser; Pharmacokinetics of Intraocular Drug Delivery of Oregon Green 488–Labeled Triamcinolone by Subtenon Injection Using Ocular Fluorophotometry in Rabbit Eyes. Invest. Ophthalmol. Vis. Sci. 2008;49(10):4506-4514. doi: 10.1167/iovs.08-1989.
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purpose. To evaluate the transscleral delivery of Oregon Green–labeled triamcinolone acetonide (OGTA) into the eye.
methods. Ex vivo experiments were performed on rabbit sclera in a Lucite block perfusion chamber. Two hundred microliters OGTA (5 mg/mL) was placed on the outer surface of the sclera for 24 hours. The exposed sclera was divided into two pieces; one half for a washout of OGTA and the other for histology. The concentration of OGTA that diffused through the sclera (n = 6) was measured by fluorometry. Two hundred microliters of OGTA (5 mg/mL) was also injected subtenon into live (n = 6) and euthanatized rabbits (n = 3). Intraocular OGTA concentrations were measured by ocular fluorophotometry.
results. The permeability constant for the transscleral diffusion (K trans) of OGTA was 1.12 × 10−7 ± 0.08 cm/s (n = 8) during the steady state perfusion. Washout tests showed higher OGTA concentration in the sclera exposed to OGTA for 4 hours than in that exposed for 1 hour. Fluorescent microscopy showed OGTA fluorescence throughout the exposed sclera, as evidence of scleral penetration of OGTA. The maximum OGTA concentration in the retina/choroid after subtenon injection was 25.77 ± 10.26 ng/mL in the live rabbit at 3 hours and 84.68 ± 21.04 ng/mL in the euthanatized rabbits at 8 hours.
conclusions. OGTA is capable of diffusing across isolated rabbit sclera ex vivo and into the retina/choroid via transscleral diffusion from a subtenon depot in vivo. Conjunctival and choroidal circulation decreased the drug delivery of OGTA.
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