Permeability of chemical delivery systems across rabbit corneal (SIRC) cell line and isolated corneas: A comparative study

The purpose of this study was to investigate the corneal permeability of phenylephrone chemical delivery systems (CDS) across isolated cornea and to evaluate the utility of the SIRC cell line (epithelial cells originating from rabbit cornea) as an in vitro model for predicting the ocular permeability. The effect of benzalkonium chloride (BAC) on the drug permeability through SIRC cell layers was also studied. The transport of phenylephrone CDS across the isolated cornea of the albino rabbit was measured at various pH values using a two-chamber glass diffusion cell, and the results were compared with the reported permeability values across SIRC cells of rabbit origin. Corneal membranes showed lower flux values for compounds, especially for hydrophilic compounds, than the SIRC cell line. A significant correlation was observed between the permeability coefficients through corneal membranes and SIRC cells. When the pH of the transport medium was increased, the permeability coefficients increased and lag times decreased in both in vitro models. Furthermore, both in vitro models showed significant correlation between permeability coefficients and lipophilicities of the drugs. The three esters, having higher lipophilic characteristics, showed higher permeability than phenylephrine HCl. The phenylacetyl ester of phenylephrone showed a three-fold increase in penetrating across SIRC cell layers in the presence of 0.01% BAC. These results suggest that the use of SIRC cell layers can reasonably predict the permeability of ophthalmic drugs across corneal membranes.