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Abstract
The relative ability of two of the most widely used ophthalmic prednisolone formulations to suppress inflammation in the cornea with an intact epithelium was determined. Use was made of an experimental model which permits objective quantitdtion of corneal inflammation. The inflammatory response was induced by the injection of clove oil directly into the corneal stroma, resulting in the chemotactic attraction of large numbers of polymorphonuclear leukocytes to the site. These cells were previously systemically labeled with intravenously administered tritiated thymidine, and the degree of radioactivity in the cornea was measured by scintillation counting techniques. That the radioactivity is primarily associated with the invading polymorphonuclear leukocytes has been verified by radioautography. The magnitude of the decrease in corneal radioactivity following topical administration of prednisolone provides an objective measure of the degree of involution of labeled polymorphonuclear leukocytes effected by each drug, and thus a measure of its anti-inflammatory effectiveness. The results document that prednisolone acetate 1.0 per cent ophthalmic suspension is more effective than prednisolone phosphate 1.0 per cent ophthalmic solution in suppressing comeal inflammation. Comparison of the present data with comparable studies of dexamethasone provide the following relative values for mean decrease in comeal inflammatory activity: (1) prednisolone acetate 1.0 per cent ophthalmic suspension, 51 per cent; (2) dexamethasone alcohol 0.1 per cent ophthalmic suspension, 40 per cent; (3) prednisolone phosphate 1.0 per cent ophthalmic solution, 28 per cent; (4) dexamethasone phosphate 0.1 per cent ophthalmic solution, 19 per cent; and (5) dexamethasone phosphate 0.05 per cent ophthalmic ointment, 12 per cent. It is emphasized that the relative order of corneal anti-inflammatory potency reported here applies only to the situation in which the epithelium of the inflamed cornea is intact.