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J. W. Higuchi, W. I. Higuchi, S. K. Li, S. A. Molokhia, D. J. Miller, R. P. Kochambilli, K. Papangkorn, D. C. Mix, Jr., A. L. Tuitupou; Noninvasive Delivery of a Transscleral Sustained Release Depot of Triamcinolone Acetonide Using the Visulex® Device to Treat Posterior Uveitis. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5822.
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To evaluate the Visulex iontophoretic ocular drug delivery system for posterior eye diseases treatable by triamcinolone acetonide (TA) through the following supporting studies: 1) pharmacokinetics, 2) efficacy, and 3) magnetic resonance imaging (MRI).
Iontophoresis of triamcinolone acetonide phosphate (TAP) was performed on the eyes of healthy New Zealand white rabbits under a current intensity of 3.0 mA for 20 minutes using a Visulex sustained release formulation of 0.5 M TAP in vivo. The pharmacokinetics study examined TA and TAP amounts delivered into the eye. Drug distributions in rabbit ocular tissues were determined by dissection of the eyes and HPLC assay. The efficacy study evaluated the transscleral delivery system treatment of lipopolysaccharide (LPS) induced posterior uveitis in rabbits by direct ophthalmologic examination. For the MRI study, a manganese ion contrast agent, as part of a precipitating sustained release depot formed by the Visulex treatment, was tracked visually at different time points to determine the distribution of agents released from depot.
In the pharmacokinetics study, the amounts of TAP and TA delivered at T=0 hr into the sclera and retina/choroid sections were 0.3 and 0.03 mg, respectively, using the Visulex system. Significant levels also were found in similar tissue samples dissected from other eyes at later time points. The results in the efficacy study showed a significant improvement in the uveitis score of the eyes treated by Visulex/TAP. The MRI study showed noticeable distribution of the contrast agent from the precipitating drug depot toward the back of the eye.
The aforementioned studies support that the Visulex sustained release system can deliver noninvasively a therapeutically relevant dose of TAP/TA for treatment of posterior eye diseases. Further studies need to be performed to evaluate completely the distribution of agents released over time from the Visulex formed drug depots.
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