Efficacy of brimonidine 0.2% and dorzolamide 2% as adjunctive therapy to beta-blockers in adult patients with glaucoma or ocular hypertension

Background: The alpha-adrenergic agonist brimonidine and the carbonic anhydrase inhibitor dorzolamide have been studied both as monotherapy and in combination with betablockers in the treatment of glaucoma and ocular hypertension: however, a MEDLINE (R) literature search failed to reveal any clinical studies directly comparing these 2 agents as adjunctive therapy. Objective: The purpose of this study was to compare the intraocular pressure (IOP)lowering efficacy of brimonidine and dorzolamide as adjunctive therapy to beta-blockers in adult patients with glaucoma or ocular hypertension. Methods: In a prospective, investigator-masked. multicenter, parallel-design clinical trial, adult patients whose IOP was inadequately controlled with topical beta-blocker therapy were randomly assigned to receive brimonidine 0.2% twice daily or dorzolamide 2% 3 times daily as adjunctive therapy for 3 months. Efficacy was determined by the reduction in IOP from baseline. After 1 month of adjunctive treatment, patients who failed to meet a target 15% reduction in IOP at peak drug effect were crossed over to the other study medication. Results: A total of 106 patients were treated. Approximately 70% (74/106) of the patients were white, and 61.3% (65/106) had a diagnosis of open-angle glaucoma. Mean baseline IOP (ie, with beta-blocker monotherapy) was comparable between treatment groups (similar to 21 mm Hg). After I month of adjunctive treatment, the mean daily IOP reduction was significantly greater with brimonidine (4.40 mm Hg, 20.4%) than with dorzolamide (3.0 mm Hg, 14.4%: P = 0.033). At peak drug effect at month II the mean IOP reduction was significantly greater in the brimonidine group (5.95 mm Hg, 27.6%) than in the dorzolamide group (4.11 mm Hg, 19.7%: P = 0.007). Significantly more patients treated with brimonidine (44/51, 86.3%) than with dorzolamide (29/47, 61.7%) achieved the target 15% reduction in IOP at month 1 (P = 0.005). At month 3, the mean daily IOP reduction and the mean IOP reduction at peak drug effect were not significantly different in the 2 treatment groups. The mean daily IOP reduction was 4.98 mm HE in the brimonidine group and 3.15 mm Hg in the dorzolamide group (P = 0.092). At peak drug effect, the mean IOP reduction was 6.39 mm HE with brimonidine acid 4.06 mm Hg with dorzolamide. The incidence of adverse events leading to discontinuation was 9.3% (5/54) in the brimonidine group (depression. 2; allergic conjunctivitis, 1: dry mouth and tearing, 1; dermatitis, 1) and 9.8% (5/51) in the dorzolamide group (ocular burning and stinging, 2, ocular itch, 1; gastrointestinal complaints, 1, lack of tolerance for beta-blocker, 1). with no significant difference between groups. Conclusion: In this trial, brimonidine 0.2% twice daily produced greater mean decreases in IOP and was effective in more patients than dorzolamide 2% 3 times daily when used as adjunctive therapy to beta-blockers.