Comparison of ocular hypotensive actions of fixed combinations of brimonidine/timolol and dorzolamide/timolol.

Objective: To compare brimonidine/timolol fixed combination (BrTFC; Combigan *) with dorzolamide/timolol fixed combination (DTFC; Cosopt dagger) in terms of ability to lower intraocular pressure (IOP) in primary open-angle glaucoma (POAG).

Methods: This was a prospective, randomized, double-masked, crossover study. After 6 weeks of therapy with timolol maleate 0.5% twice daily, patients were randomized to BrTFC twice daily or DTFC twice daily for 6 weeks, before being crossed over to the other treatment arm for a further 6 weeks. At all follow-up visits, IOP was measured at 09.00 (pre-instillation) 12.00 and 16.00. The primary outcome measure was change in mean diurnal IOP from baseline at 6 weeks. The secondary outcome was percentage of patients with IOP <18 mmHg at 6 weeks. Data were analyzed from all patients who completed the study.

Results: Twenty-five patients were randomized and 20 completed the study. Mean diurnal IOP (mean +/- standard deviation [SD]) was 20.28 +/- 2.03 mmHg at timolol-treated baseline. After 6 weeks, mean diurnal IOP was 16.28 +/- 2.07 mmHg following BrTFC and 17.23 +/- 2.29 mmHg following DTFC (difference: 0.95 mmHg, 95% CI 0.10-1.80, p = 0.03). Mean IOP at 09.00 was 20.95 +/- 2.31 mmHg at baseline. This was reduced to 15.85 +/- 2.56 mmHg following BrTFC and 17.55 +/- 2.67 mmHg following DTFC (difference: 1.70, 95% CI 0.80-2.60, p = 0.001). For the 12.00 and 16.00 timepoints, the mean changes from baseline in the two arms were comparable. Percentages of patients achieving a target IOP of <18 mmHg were 85% following BrTFC and 60% following DTFC (p = NS [not significant]). No treatment-related adverse events were reported with either therapy. Key limitations include the small size of the study population and the 6-week duration of treatment periods, which prevents drawing conclusions regarding long-term therapy.

Conclusion: Reductions from baseline in mean diurnal IOP and morning IOP were greater with BrTFC than with DTFC.