Background: Brimonidine and dorzolamide are intraocular pressure (IOP)-lowering medications most commonly used in second-line treatment of glaucoma and ocular hypertension.

Scope: An evidence-based review of comparative clinical trials of brimonidine and dorzolamide was undertaken to determine the relative efficacy and safety of these drugs in reducing IOP. Using the keywords ‘brimonidine’ and ‘dorzolamide’, all articles describing such trials from September 1966 to July 2007 were found in MEDLINE and EMBASE.

Findings: In all identified studies, brimonidine and dorzolamide were both found to provide significant IOP reduction from treated or untreated baseline levels. Results of eight trials reported to date indicate that brimonidine produced either a lower treated IOP or greater pressure reduction from baseline than dorzolamide at one or more measured timepoints, and provided comparable IOP lowering over all other measurements. Differences between the IOP reductions provided by brimonidine and dorzolamide were more pronounced when the medications were used adjunctively with other classes of drugs. Six other trials showed similar efficacy, and one additional monotherapy study showed lower IOP with dorzolamide treatment. Ocular burning was noted with dorzolamide more than any other adverse event with either drug. Trials ranged widely in duration of therapy and the time of day IOP measurements were taken, and many were too small for sufficient statistical power.

Conclusion: Brimonidine and dorzolamide are both efficacious and reasonably well tolerated. Possible overall distinctions in efficacy were obscured by differences in study designs and treatment regimens, but adjunctive therapy with brimonidine may reduce IOP as effectively or more effectively than adjunctive or fixed combination dorzolamide therapy. In certain patients with glaucoma and ocular hypertension brimonidine may be a better choice than dorzolamide for second-line treatment.