Comparative acute effects of brimonidine 0.2% versus dorzolamide 2% combined with beta-blockers in glaucoma

Purpose: To assess the acute intraocular hypotensive efficacy of brimonidine tartrate 0.2% (a highly selective alpha(2)-adrenergic agonist) compared with dorzolamide 2% (a topical carbonic anhydrase inhibitor) as adjunct therapy to topical beta-blockers in patients with primary open-angle glaucoma. Methods: A randomized cross-over masked study was performed. We enrolled one eye of each of 28 patients who were on different beta-blocker therapy. We measured the intraocular pressure (IOP) 2 h after the beta-blocker instillation; we then randomly administered one of the two drugs and we compiled an IOP diurnal curve. One month later we repeated the same procedures with the second drug. Unpaired Mann-Whitney U-test was used to compare decreases in IOP between the two drugs (P<0.05). Results: Both brimonidine 0.2% and dorzolamide 2% have good ocular hypotensive efficacy, significantly lowering IOP when compared to beta-blocker therapy alone, for the whole diurnal curve. Maximum mean percent IOP decrease from baseline was 22.0+/-15.7% (4.0+/-2.9 mmHg) for dorzolamide 2% 6 h after instillation and 35.5+/-16.4% (7.0+/-4.1 mmHg) for brimonidine 0.2% 8 h after administration of the drug. When we compared the two treatments, brimonidine 0.2% showed a higher hypotensive effect than 2% dorzolamide after 3 h (28.4+/-16.8% vs 17.6 +/-9.3%; P=0.04) and 8 h (35.5+/-16.4% vs 21.6+/-10.8%; P=0.04). Conclusion: This study indicates that 0.2% brimonidine acutely associated with beta-blockers is an interesting new combination treatment useful in the management of glaucoma.