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

Abstract

Objective:

To compare brimonidine/timolol fixed combination (BrTFC; Combigan with dorzolamide/timolol fixed combination (DTFC; Cosopt 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.

Key words:

• Brimonidine
• Dorzolamide
• Dorzolamide
• timolol combination
• Glaucoma, open angle
• Intraocular pressure
• Timolol

Transparency

Declaration of funding

This study was supported in part by the Instituto de Salud Carlos III, Madrid, Spain (Proyecto RD 07/0062: ‘Patología ocular del envejecimiento, calidad visual y calidad de vida’). Editorial assistance was funded by Allergan Ltd.

Declaration of financial/other relationships

J.G.-F. has disclosed that he has received research grants from Pfizer, Merck, Sharp & Dohme and Alcon. J.M.M. has disclosed that he has received research grants from Pfizer, Merck and Alcon. A.F.-V. and J.G.-S. have disclosed that they have received research grants from Pfizer.

Some peer reviewers receive honoraria from CMRO for their review work. The peer reviewers of this paper have disclosed that they have no relevant financial relationships.

Acknowledgments

Editorial assistance was provided by Darwin Healthcare Communications. All data analyses were conducted by the authors.

Notes

*Combigan is a registered trademark of Allergan Inc., Irvine, CA, USA.

†Cosopt is a registered trademark of Merck and Co. Inc., NJ, USA.

*Combigan is a registered trademark of Allergan Inc., Irvine, CA, USA.

†Cosopt is a registered trademark of Merck and Co. Inc., NJ, USA.