Quantitative evaluation of ocular anti-inflammatory drugs based on measurements of corneal temperature in rabbits: dexamethasone and glycyrrhizin.

A method for the quantitative evaluation of topically applied anti-inflammatory agents is described. Conjunctival inflammation was induced in rabbits by topical instillation of n-butanol. The intensity of inflammation was determined by measuring changes of corneal surface temperature with an infrared thermometer. The closest correlation was obtained between corneal temperature change and the Draize score which is widely used as a subjective scoring method. Dexamethasone showed a good logarithmic dose-response inhibitory effect between 0.0001 and 0.1%, and glycyrrhizin the same at 0.25-5%. Glycyrrhizin in a 5% solution showed a comparable anti-inflammatory effect to that of dexamethasone (0.1%). The inflammation model induced by n-butanol was mediated, in part, by the degranulation of mast cells because of some inhibitory effect of disodium cromoglycate (2%), an inhibitor of mast cell degranulation, and diphenhydramine hydrochloride (0.5%), an antihistaminic agent.