Effects of brinzolamide on aqueous humor dynamics in monkeys and rabbits.

This study examines the mechanisms by which brinzolamide reduces intraocular pressure (IOP) in healthy rabbits and in monkeys with unilateral ocular hypertension. Intraocular pressures were measured by pneumatonometry and aqueous flow was determined by fluorophotometry before and after three twice-daily drops of 1% brinzolamide to both eyes per monkey and after similar treatment to one eye per rabbit. In monkeys, outflow facility was determined by fluorophotometry and uveoscleral outflow was calculated. In rabbits, outflow facility was determined by two-level constant pressure infusion and uveoscleral outflow was measured by an intracameral tracer technique. Compared with contralateral vehicle-treated rabbit eyes, IOP was reduced in brinzolamide-treated eyes by 2.5 +/- 1.9 mmHg (mean +/- standard deviation; p =.006) at four hours after the second dose. Aqueous flow was reduced by 0.50 +/- 0.65 microl/min (p =.02). This effect was found in rabbits previously treated with brinzolamide but not in naive rabbits. Treated hypertensive eyes of monkeys had a reduction in IOP of 7.3 +/- 8.8 mmHg (p = 0.01) and aqueous flow of 0.69 +/- 1.10 microL/min (p = 0.05) when compared with baseline. Brinzolamide did not affect outflow facility or uveoscleral outflow in either rabbits or monkeys. It is concluded that, in normotensive eyes of rabbits and hypertensive eyes of monkeys, brinzolamide reduces IOP by reducing aqueous flow and not by affecting aqueous humor drainage.