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Enhancement and inhibition effects on the corneal permeability of timolol maleate: polymers, cyclodextrins and chelating agents

Rodríguez, I., Vázquez, J. A., Pastrana, L. and Khutoryanskiy, V. V. (2017) Enhancement and inhibition effects on the corneal permeability of timolol maleate: polymers, cyclodextrins and chelating agents. International Journal of Pharmaceutics, 529 (1-2). pp. 168-177. ISSN 0378-5173

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To link to this item DOI: 10.1016/j.ijpharm.2017.06.075

Abstract/Summary

This study investigates how both bioadhesive polymers (chitosan, hyaluronic acid and alginate) and permeability enhancers (ethylene glycol- bis(2-aminoethylether)- N, N, N', N'- tetraacetic acid (EGTA) and hydroxypropyl-ß-cyclodextrin) influence the permeability of the anti-glaucoma drug timolol maleate through ex vivo bovine corneas. Our results showed that only the permeability enhancers alone were able to increase drug permeability, whereas the polymers significantly reduced drug permeation, and however, they increased the pre-corneal residence of timolol. Ternary systems (polymer-enhancer-drug) showed a reduced drug permeability compared to the polymers alone. Fluorescence microscopy analysis of the epithelium surface confirmed there was no evidence of epithelial disruption caused by these formulations, suggesting that polymer-enhancer interactions reduce drug solubilization and counteract the disruptive effect of the permeability enhancers on the surface of the cornea. Further mucoadhesive tests, revealed a stable interaction of chitosan and hyaluronic acid with the epithelium, while alginate showed poor mucoadhesive properties. The differences in mucoadhesion correlated with the permeability of timolol maleate observed, i.e. formulations containing mucoadhesive polymers showed lower drug permeabilities. The results of the present study indicate polymers acting as an additional barrier towards drug permeability which is even more evident in the presence of permeability enhancers like EGTA and hydroxypropyl-ß-cyclodextrin. Then, this study highlights the need to adequately select additives intended for ocular applications since interactions between them can have opposite results to what expected in terms of drug permeability.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > School of Pharmacy > Pharmaceutics Research Group
ID Code:71721
Publisher:Elsevier

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