Effects on aqueous flow of dorzolamide combined with either timolol or acetazolamide

To determine the effect on aqueous flow of topical dorzolamide 2%, topical timolol 0.5%, or oral acetazolamide 250 mg when used alone or when dorzolamide is combined with either timolol or acetazolamide.

In 30 patients with ocular hypertension, aqueous flow and intraocular pressure (IOP) were determined at baseline and on the following combinations of drugs in a crossover design: (1) vehicle alone, (2) dorzolamide alone, (3) acetazolamide alone, (4) timolol alone, (5) dorzolamide + acetazolamide, and (6) dorzolamide + timolol. Treated eyes were compared with control eyes and comparisons were made between treatments.

Compared with baseline, significant (P < 0.04) IOP reductions in the order of efficacy were: dorzolamide + timolol > dorzolamide + acetazolamide = acetazolamide = timolol > dorzolamide. Aqueous flow was reduced more by dorzolamide + timolol than by each drug alone (P < 0.04) and more by dorzolamide + acetazolamide than by dorzolamide alone (P < 0.04).

The combination of dorzolamide and timolol demonstrated significant aqueous flow additivity and had greater IOP efficacy than the combination of dorzolamide and acetazolamide.