Influence of some preservatives on the corneal permeability of pilocarpine and dexamethasone, in vitro

Abstract The influence of some commonly used preservatives on the corneal permeability and uptake of pilocarpine and dexamethasone were investigated in vitro. Isolated corneas were exposed to benzalkonium chloride (0.01%), chlorobutanol (0.5%), metagin (0.04%) + propagin (0.02%), and chlorhexidine digluconate (0.01%), all in clinically used concentrations, for 4 h at 35 °C. Benzalkonium chloride and chlorobutanol significantly increased the uptake and permeability of the two drugs. The influence of the parabens was of lower magnitude and the effect of chlorhexidine digluconate resulted in small or insignificant changes of the studied parameters. The barrier function of the corneal epithelium was strong. Both drugs showed a significant increase in permeability and uptake when de-epithelized corneas were used. Abrasion of the epithelium or preservatives showed a more pronounced influence on the corneal permeability and uptake for dexamethasone than pilocarpine HCl.