Effect of brinzolamide and dorzolamide on aqueous humor flow in human eyes.

PURPOSE: To measure the relative efficacy of brinzolamide hydrochloride 1% ophthalmic suspension, a new carbonic anhydrase inhibitor, compared with the currently used dorzolamide hydrochloride 2% ophthalmic solution as suppressors of aqueous humor flow in human eyes, and to study the difference of effect during the day and at night. METHODS: A randomized, double-masked, placebo-controlled study of 25 normal human subjects was carried out at Mayo Clinic. The daytime rate of aqueous humor flow was measured every 2 hours from 8 AM to 4 PM by means of fluorophotometry. Likewise, the night-time rate of aqueous humor flow was measured every 2 hours from 12 AM to 6 AM. Intraocular pressure was measured at 4 PM and 6 AM. RESULTS: Brinzolamide reduced aqueous flow by 0.47+/-0.20 microl per min (mean+/-SD) during the day, whereas dorzolamide reduced flow by 0.34+/-0.20 microl per min. Brinzolamide reduced aqueous flow by 0.16+/-0.12 microl per min during the night, whereas dorzolamide reduced flow by 0.10+/-0.13 microl per min. Brinzolamide reduced afternoon intraocular pressure by 1.5+/-1.1 mm Hg, and dorzolamide reduced afternoon intraocular pressure by 1.1+/-1.0 mm Hg. Brinzolamide reduced the morning awakening intraocular pressure by 0.3+/-1.6 mm Hg, and dorzolamide reduced it by 0.8+/-1.0 mm Hg. CONCLUSIONS: Our data support the idea that brinzolamide is at least as efficacious as dorzolamide as a suppressor of aqueous humor flow in normal human eyes and that there is probably not a clinically significant difference between the two drugs in this efficacy. Clinicians who prescribe brinzolamide should expect similar ocular hypotensive responses from brinzolamide and dorzolamide.