Brimonidine. A Review of Its Pharmacological Properties and Clinical Potential in the Management of Open-angle Glaucoma and Ocular Hypertension

Brimonidine is a highly selective alpha 2-adrenoceptor agonist which reduces intraocular pressure (IOP) by reducing aqueous humour production and increasing aqueous humour outflow via the uveoscleral pathway. Brimonidine is indicated for the topical management of open-angle glaucoma or ocular hypertension. In 3 large comparative studies in patients with open-angle glaucoma or ocular hypertension, the ocular hypotensive efficacy of brimonidine was maintained during treatment periods of up to 1 year. Mean reductions in peak (measured 2 hours after the morning dose) and trough (measured 12 hours after the evening dose) IOP were 5.6 to 5.9 and 3.3 to 3.7 mm Hg, respectively, after 3 or 12 months of treatment with brimonidine 0.2% twice daily. The efficacy of brimonidine in this setting was similar to that of timolol 0.5% twice daily at peak only (-6.0mm Hg), and superior to that of betaxolol 0.25% twice daily at both peak (-3.5mm Hg) and trough (-2.7mm Hg). When added to topical beta-adrenoceptor antagonist therapy, initial results showed brimonidine 0.2% twice daily to have additive ocular hypotensive efficacy similar to that of pilocarpine 2% 3 times daily. Thus, brimonidine 0.2% may be a useful adjunct in this setting. According to combined data from 2 large comparative studies, the most frequent adverse events associated with brimonidine therapy were oral dryness (30.0% of patients), ocular hyperaemia (26.3%) and ocular burning and/or stinging (24.0%). Ocular allergic reactions including allergic blepharitis, blepharoconjunctivitis and follicular conjunctivitis occurred with an incidence of 9.6% in 1 study. In a third comparative study, the incidence of adverse events associated with brimonidine therapy was lower, with conjunctival hyperaemia (11.4%) the most frequently reported event. Changes in systolic and diastolic blood pressure and, to a lesser extent, heart rate have been reported in patients treated with therapeutic doses of topical brimonidine for up to 12 months, but these changes were not clinically significant. Unlike beta-adrenoceptor antagonists, brimonidine is not contraindicated in patients with cardiopulmonary disease, although it should be used with caution in individuals with severe cardiovascular disease. Thus, further studies are warranted to determine the efficacy of brimonidine when used in combination with other glaucoma medications and its efficacy relative to newer drugs such as dorzolamide and latanoprost. However, available data suggest that brimonidine is a promising alternative option for the lowering of IOP in the management of open-angle glaucoma and ocular hypertension, particularly in patients with cardiopulmonary disease in whom topical beta-adrenoceptor antagonist therapy is contraindicated.