Efficacy of nedocromil sodium and cromolyn sodium in an experimental model of ocular allergy

Background: Because ocular allergic disorders are important in terms of frequency and severity, there is a constant search for new topical antiallergic drugs. Nedocromil sodium has recently been introduced as a potential substitute for the mast cell stabilizer cromolyn sodium. Objective: We compared the efficacy of topical 2% nedocromil sodium to that of 2% cromolyn sodium in treatment of the early-phase reaction of an experimental model of allergic conjunctivitis. Methods: Guinea pigs were challenged topically with egg albumin 14 days after systemic immunization. Fifteen minutes before, immediately prior to, and 15 minutes after topical challenge, the animals received either 2% nedocromil sodium or 2% cromolyn sodium topically in one eye and phosphate buffered saline (PBS) in the other eye. Antigen-induced increase in vascular permeability was measured by the extravasation of intravenously injected Evans blue dye. Animals that were immunized and topically challenged but did not receive Evans blue were used for histologic studies. Results: Evans blue extravasation from ocular tissues significantly decreased in drug-treated eyes compared with PBS-treated eyes (P < .01). Further, the cellular infiltrate (mast cells, eosinophils, and neutrophils) in the substantia propria of the conjunctiva was markedly reduced in the drug-treated eyes. No significant difference was observed between the nedocromil sodium- or cromolyn sodium-treated eyes. Conclusions: Topical 2% nedocromil sodium reduces the early-phase reaction of the allergic response as effectively as 2% sodium cromoglycate in a guinea pig model of ocular anaphylaxis.