Purpose: 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. Methods: 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. Results: 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). Conclusion: The combination of dorzolamide and timolol demonstrated significant aqueous flow additivity and had greater IOP efficacy than the combination of dorzolamide and acetazolamide.
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