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S. Brocchini, D. J. Paull, Q. Ru, P. T. Khaw; Determining the Concentration of the MMPi Ilomastat in Ocular Tissues Using HPLC. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2448.
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The wound healing response following Glaucoma Filtration Surgery (GFS) requires modulation over a period of time. Tissue tablets containing Ilomastat, a Matrix Metalloproteinase inhibitor (MMPi) have been developed to inhibit scarring post-GFS. An important aspect in the development of these tablets is to understand the pharmacokinetics and tissue distribution. We therefore developed a method for detection of Ilomastat in a range of ocular tissues using High Performance Liquid Chromatography (HPLC).
Ocular tissue, including the conjunctiva, sclera and muscle were dissected from rabbit eyes and soaked in 100 µM Ilomastat for 24 hours. The tissue was then freeze-dried before being digested in Collagenase D (1.0 mL, 2mg/ml) for up to 48 hours. The liquid was then analysed for Ilomastat concentrations using HPLC. The same method was then used to detect levels of Ilomastat following the creation of an artificial bleb in an ex-vivo model. A tablet was placed under an artificial bleb with flow (2 µl/min) passed through the subconjunctival space using a pump. Eyes were maintained for either 4 or 24 hours before tissue digestion and Ilomastat detection.
The method of tissue digestion and drug detection was first demonstrated using ocular tissues soaked in Ilomastat solution, where concentrations ranging from 0.07µM to 0.15µM were found. In the ex-vivo model, we found that 4 hours after exposure, Ilomastat was detectable in the conjunctiva at a concentration of 0.44µM/mg increasing to 0.52µM/mg after 24 hours. Similar results were found in other regions of the eye. Controls of Ilomastat solution were analysed with the same methodology and approximately 10% of Ilomastat was lost during processing.
From these results we have determined the concentrations of Ilomastat in a range of ocular tissues. This will now be correlated to the ocular tissue distribution from an in-vivo model of GFS to aid our efforts in developing a tissue tablet to release Ilomastat for prolonged periods.
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