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 α₂-adrenergic agonist) compared with dorzolamide 2% (a topical carbonic anhydrase inhibitor) as adjunct therapy to topical β-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 β-blocker therapy. We measured the intraocular pressure (IOP) 2 h after the β-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 β-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 4 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 β-blockers is an interesting new combination treatment useful in the management of glaucoma. Received: 29 July 1999 Revised: 14 September 1999 Accepted: 29 September 1999