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Helena Filipe, Raquel Galante, Daniela Ghisleni, Marina Braga, Terezinha J. A. Pinto, Rogério Colaço, Ana Paula Serro; Diclofenac Loaded Soft Contact Lenses: in vitro studies towards the development of safe and efficient devices . Invest. Ophthalmol. Vis. Sci. 2017;58(8):3067.
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© ARVO (1962-2015); The Authors (2016-present)
Contact lenses have been studied as platforms for topical corneal drug delivery, capable of increasing bioavailability in at least 50% when compared to eyedrops (1-5%). However, there is a lack of knowledge concerning the possible effects of sterilization on the drug release behavior from those devices.The main goal of this work was to evaluate the impact of two commonly used sterilization methods, gamma irradiation and steam heat, on the release of diclofenac from a silicone hydrogel (Si-Hy) soft contact lenses
The Si-Hy was produced in lab by thermospolymerization and loaded with the drug by soaking in diclofenac solution. Performing control contamination with different loads of the specific biologic indicator, i. e,. specific resistant microorganisms for each method (Bacillus pumillus for gamma irradiation and Geobacillus stearothermophilus for steam heat) ensured the effectiveness of the sterilization procedures. In vitro drug release tests were conducted in sink conditions. The amount of drug released was quantified by high performance liquid chromatography (HPLC). Considering the hydrodynamic conditions of the eye, a mathematical model was applied to the results to estimate the in vivo efficacy of the loaded devices in comparison to commercially available diclofenac eyedrops.
Gamma irradiation (10 kGy) led to significant reduction of the total released drug amount with formation of degradation products, being only effective in sterilizing microbial loads under 104 CFU/mL. Steam heat was effective in sterilizing all contaminated samples yet, induced ~50% reduction of the total released drug amount, but no degradation products were observed. Concerning in vivo efficacy estimation and according to the applied model, after each eyedrop instillation the diclofenac concentration remained above 10% of its initial concentration value for 15 min. The unsterilized loaded Si-Hy, rises this time to at least 96h. After the steam heat sterilization the residence time falls to below 28h.
Our findings offer relevant insights about the feasibility of producing safe and effective diclofenac loaded daily contact lenses, using a simple methodology.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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