Objective: To determine the ocular hypotensive efficacy and safety of dorzolamide when added to brimonidine or timolol in patients with uncontrolled primary open-angle glaucoma (POAG).

Methods: This is a 1-year prospective open-label clinical trial of 48 consecutive POAG patients with inadequate intraocular pressure (IOP) control while using brimonidine 0.2% (23 patients) and timolol 0.5% (25 patients), 2 times daily. Patients were assigned to receive dorzolamide 2% as adjunctive therapy, added 3 times daily to brimonidine or timolol. IOP was measured on week 2, and months 3, 6, 9, and 12.

Results: A significant reduction in IOP from the baseline was observed after dorzolamide use in both groups at visits during that year (P < 0.001). Overall, mean IOP reduction was 5.6 +/- 1.9 mmHg with the brimonidine-dorzolamide combination, and 6.8 +/- 1.7 mmHg with timolol-dorzolamide after 1 year of treatment; the difference was significant (P = 0.029). No statistical differences existed between the groups for adverse events (P < 0.05).

Conclusions: The addition of dorzolamide to brimonidine or timolol has significant IOP-lowering efficacy during 1 year in patients with POAG whose IOPs were inadequately controlled with brimonidine or timolol alone. The IOP-lowering effect of the timolol-dorzolamide combination at 1 year was more pronounced than brimonidine-dorzolamide. Both combinations were well-tolerated by the patients.