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Y. C. Yang, S. Chen, V. Chong, J. Gibson, B. R. Conway; In vitro Trans-Scleral Permeation of Dexamethasone Formulations. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5315.
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Surfactants (such as tyloxapol) or cyclodextrins (cyclical oligosaccharide glucose molecules) are known to enhance solubility and transdermal permeation of drugs. This research is to investigate the permeability of dexamethasone-containing formulations containing potential enhancers though porcine sclera, in an in vitro model.
0.1 % w/v Dexamethsone (Acros) , 1.5% w/v 2 -hydroxypropyl-β-cyclodextrin (HPβCD) (Alrich), 0.1% w/v hydroxypropyl methylcellulose (HPMC) 4000 (HPMC) and 0.05% sodium edetate were stirred in BSS Plus Intraocular Irrigating Solution (Alcon) at room temperature for 12 hours to form a complex. A suspension containing dexamethasone and 0.4% w/v tyloxapol in room temperature for 12 hours. Isolated porcine sclerae were mounted between the donor and receiver chambers of vertical Franz type diffusion cells containing BSS PLUS in the receiver maintained at 37°C. One mL of dexamethasone solution (0.1 %w/v) or formulations was added to the donor chamber and samples withdrawn from the receptor chamber at predetermined time intervals, replaced with the same volume of fresh medium and subsequently assayed by HPLC.
Both cyclodextrin- and tyloxapol -containing formulations increased the drug penetration rate (figure 1). The amount of free drug in the cyclodextrin- and the tyloxapol-containing formulations was 0.05% and 0.15% w/v respectively.
The in vitro diffusion model is capable of differentiating between different formations and trans-scleral delivery is affected by the dissolved drug concentration. Both cyclodextrin and surfactant increased the drug solubility effectively and may be useful excipients in trans-scleral drug delivery strategies.Figure 1 Penetration of dexamethasone through sclera over 12 hours (n=5; mean±s.d.)
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