Incidence of brimonidine allergy in patients previously allergic to apraclonidine

Purpose: This study was performed to determine the incidence of allergic re action to brimonidine in patients who have previously demonstrated an aller gic reaction to apraclonidine. Methods: A retrospective chart review was performed to identify patients wh o had demonstrated an allergic reaction to apraclonidine of sufficient seve rity to result in drug discontinuation. Within this group, those patients s ubsequently treated with brimonidine were isolated and analyzed, and the in cidence of allergy to brimonidine was determined. Results: Forty-five patients were identified with a significant allergic re action to apraclonidine that resulted in drug discontinuation. Of these pat ients, 22 subsequently received brimonidine. Follow-up on all patients was obtained for at least 15 months. All but two of the 22 patients were taking additional topical glaucoma medications, ranging from one to three additio nal agents with an average of 1.8 +/-:0.8 medications. Seventeen patients i ncurred no allergic reaction to brimonidine. Only five patients (22.7%) pre viously allergic to apraclonidine developed an allergic reaction to brimoni dine. Three of these patients demonstrated only a follicular conjunctival r eaction, one had conjunctival hyperemia, and one patient developed a perioc ular dermatitis. The allergic reactions developed at 8.2 +/- 1.2 months aft er initiation of brimonidine therapy. Conclusions: In this study, the risk of developing an allergic reaction to brimonidine in patients known to be allergic to apraclonidine is 22.7%. Thi s lack of a strong cross-reactive allergic response possibly suggests diffe rent allergic mechanisms for these two medications. Therefore, brimonidine therapy in patients previously identified as being allergic to apraclonidin e is safe and does not result in a cross-reactive response in the great maj ority of patients (or in nearly four of five patients).