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J.J. Arnold, Y. Choksi, X. Chen, A. Shimazaki, E. Toone, D.L. Epstein, P. Challa; Hydrogel Formulations Containing (2–Hydroxypropy)–ß–Cyclodextrin and Chitosan Improve the Ocular Pharmacodynamics of the Poorly Soluble Ocular Hypotensives, Ethacrynic Acid (ECA) and SA9000 . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5104.
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Several potentially novel trabecular outflow drugs have limitations in solubility and ability to penetrate the cornea. (2–hydroxypropyl)–ß–cyclodextrin (HPBCD) has been shown to enhance the solubility of lipophilic drugs through the formation of guest–host inclusion complexes. The purpose of this work was to assess the ability of HPBCD to enhance the solubility and intraocular distribution of two potentially novel topical anti–glaucoma drugs, ethacrynic acid (ECA) and SA9000, following inclusion in formulations of chitosan (a mucoadhesive biopolymer intended to prolong drug residence time).
UV–spectroscopy was used to assess the ability of HPBCD to form inclusion complexes with ECA. To assess the mucoadhesive properties of chitosan, fluorescein was topically administered with and without the polymer to Dutch–belted (DB) rabbits, and the presence of fluorescence was assessed after 10 minutes. In vivo intraocular pressure (IOP) lowering data was obtained following single–dose administration of various topical formulations to DB rabbits. Signs of ocular toxicity were assessed at specific intervals. Cysteine adducts of the drugs were prepared as possible pro–drugs.
The ocular retention and corneal adhesion of fluorescein was significantly improved in the presence of chitosan (1%). UV–spectrophotometric data suggested that increasing concentrations of HPBCD could improve the water solubility of ECA through formation of inclusion complexes. Topical administration of ECA (1%)–cysteine adducts to DB rabbits (n= 4) resulted in minimal ocular redness, but little reduction in IOP (–1.5 (8%) ±0.4 mmHg) in the treated eyes compared to the untreated. The addition of chitosan (1%) (n= 4) or chitosan (1%) plus HPBCD (5%) (n= 5) to the ECA–cysteine formulations resulted in significantly greater reductions in IOP (–3.9 (15%) ±0.5 and –6 (24%) ±0.3 mmHg, respectively). Formulations of SA9000 (0.3%)–cysteine plus chitosan (1%) and HPBCD (5%) (n= 4) also lowered IOP (–4.1 (15%) ±0.8 mmHg) following topical administration. All of the formulations tested resulted in minimal or no ocular irritation.
These data indicate that chitosan plus HPBCD is an improved formulation for the solubilization and ocular targeting of the poorly soluble ocular hypotensives, ECA and SA9000.
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