Effects of topical application of a 2% solution of dorzolamide on intraocular pressure and aqueous humor flow rate in clinically normal dogs

Objective-To evaluate effects of topical application of a 2% solution of do rzolamide on intraocular pressure (IOP) and aqueous humor flow rate in clin ically normal dogs. Animals-15 Beagles. Procedure-The IOP was measured in both eyes of all dogs for 3 days to deter mine baseline values. In a single-dose study, 50 mul of dorzolamide or cont rol solution was applied in both eyes at 7:00 AM, and IOP was measured 7 ti mes/d. In a multiple-dose study, dorzolamide or control solution was applie d to both eyes 3 times/d for 6 days, and IOP was measured 4 times/d during treatment and for 5 days after cessation of treatment. Aqueous humor flow r ate was measured for all dogs fluorophotometrically prior to treatment and during the multiple-dose study. Results-In the single-dose study, dorzolamide significantly decreased IOP f rom 30 minutes to 6 hours after treatment. Mean decrease in IOP during this time span was 3.1 mm Hg (18.2%). Maximal decrease was detected 6 hours aft er treatment (3.8 mm Hg, 22.5%). In the multiple-dose study, dorzolamide de creased IOP at all time points, and maximal decrease was detected 3 hours a fter treatment (4.1 mm Hg, 24.3%). Mean aqueous humor flow rate decreased f rom 5.9 to 3.4 mul/min (43%) after treatment in the dorzolamide group. Conclusions and Clinical Relevance-Topical application of a 2% solution of dorzolamide significantly decreases IOP and aqueous humor flow rate in clin ically normal dogs. Therefore, topical administration of dorzolamide should be considered for the medical management of dogs with glaucoma.