Effect of Formulation Parameters on Corneal Permeability of Ofloxacin

Influence of pH, buffer, preservative, tonicity and viscosity modifiers on in vitro transcorneal permeation of ofloxacin was studied using excised goat cornea. Permeation studies were carried out by putting 1 ml of test formulation on the cornea (0.78cm) mounted between the donor and receptor compartments of an all glass modified Franz diffusion cell and measuring ofloxacin concentration in the receptor (containing bicarbonate ringer under stirring at 35°C) by spectrophotometry at 288 nm, at various time intervals up to 120 min. Buffering the formulation with phosphate buffer or use of combination of methyl and propyl paraben or benzalkonium chloride or combination of benzalkonium chloride and disodium edetate as preservative provided significant increase in the apparent corneal permeability coefficient of ofloxacin. While the use of phenyl mercuric acetate as preservative or tonicity adjustment with mannitol showed a significant decrease in apparent corneal permeability of ofloxacin. Raising the pH of test formulation from 6.4 to 7.2 or addition of hydroxyl-propyl-β-cyclodextrin or use of viscosity modifier had no significant effect on apparent corneal permeability of drug.