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Editors Selection IGR 7-1
Medical treatment
Comment by Donald Minckler on:
11923 Alphagan allergy may increase the propensity for multiple eye-drop allergy, Osborne SA; Montgomery DMI; Morris D et al., Eye, 2005; 19: 129-137
A retrospective clinic-based case series by Osborne et al. (267) analyzes presumed allergies due to topical or systemic medications among consecutive patients with primary open-angle glaucoma, ocular hypertension, or low tension glaucoma who reported discontinuing a drug because of allergic symptoms during the recruitment period May 1999 through September 2001. All 2788 clinic files were screened, from which 1237 met the study criteria including a description of first use of the drug, monocular therapy with the agent in question, and discontinuing therapy because of allergic symptoms. Twenty separate topical and systemic regimens were defined and the diagnosis of allergy by the patient or physician and assumed to be reliable. Analysis included identifying apparent cross-reactions between two agents and the role of preservatives using coefficients of association. Besides clinical parameters (IOP, cupping, visual fields, surgical success), data collected for each agent included the mean duration of treatment, a compliance estimate, side effects noted, and tachyphylaxis. The statistical methods utilized permitted analysis of the comparative likelihood of sequential allergic reactions to variable serial exposures to specific agents. The authors interpret the data as indicating that brimonidine (0.2%) among all currently utilized agents, is most likely to cause allergic symptoms (itching follicular conjunctivitis, chemosis, peri-ocular dermatitis) and most importantly that this drug predisposes and accelerates subsequent allergic reactions to other topical agents including some timolol preparations and dorzolamide. The role of the presence and concentration of benzalkonium chloride, the preservative common to most topical ocular medications, was not clarified in this study. Also no clear relationship between allergic cross-reactions from brimonidine and latanoprost nor any subsequent consequences for surgical success after a prior allergic reaction were discovered. The major criticism of this study is that it was retrospective and dependent on data extraction from clinic records without a specific protocol including definitions of allergy. Also, the numbers of some agents utilized were too small to permit meaningful statistical analysis, especially considering the number of possible variables. Nevertheless, the conclusions highlight an important issue in suggesting that a widely utilized glaucoma drug, long-recognized as relatively allergenic, may accentuate or predispose to allergy among subsequently employed agents, which by themselves are less likely to induce allergic symptoms. The conclusions imply that brimonidine is an immune stimulant and the clinical implication would be to place this agent last in the trial spectrum.
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