Incidence of brimonidine allergy in patients previously allergic to apraclonidine

Purpose: This study was performed to determine the incidence of allergic reaction to brimonidine in patients who have previously demonstrated an allergic reaction to apraclonidine. Methods: A retrospective chart review was performed to identify patients who had demonstrated an allergic reaction to apraclonidine of sufficient severity to result in drug discontinuation. Within this group, those patients subsequently treated with brimonidine were isolated and analyzed, and the incidence of allergy to brimonidine was determined. Results: Forty-five patients were identified with a significant allergic reaction to apraclonidine that resulted in drug discontinuation. Of these patients, 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 additional agents with an average of 1.8 ± 0.8 medications. Seventeen patients incurred no allergic reaction to brimonidine. Only five patients (22.7%) previously allergic to apraclonidine developed an allergic reaction to brimonidine. Three of these patients demonstrated only a follicular conjunctival reaction, one had conjunctival hyperemia, and one patient developed a periocular dermatitis. The allergic reactions developed at 8.2 ± 1.2 months after 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%. This lack of a strong cross-reactive allergic response possibly suggests different allergic mechanisms for these two medications. Therefore, brimonidine therapy in patients previously identified as being allergic to apraclonidine is safe and does not result in a cross-reactive response in the great majority of patients (or in nearly four of five patients).