Effect of Oxymetazoline on Aqueous Humor Dynamics and Ocular Blood Flow in Monkeys and Rabbits

• OBJECTIVE. —To evaluate the ocular effects of oxymetazoline hydrochloride, an α2 agonist, in cynomolgus monkeys and albino rabbits. METHODS. —Intraocular pressure was measured before and for 6 hours after application to glaucomatous monkey eyes. Outflow facility and aqueous flow rates were measured in normal monkey eyes. Uveoscleral outflow was measured in rabbit eyes. Ocular peak pulse volume was determined with the ocular blood flow system in normal and glaucomatous monkey eyes. RESULTS. —Single applications of ozymetazoline reduced (P<.001) intraocular pressure up to 6.0±1.0 mm Hg (mean±SEM). Enhancement of the ocular hypotensive effect was observed with 5-day twicedaily administration. Outflow facility was unaltered; aqueous flow rate was decreased (P<.001) by 39% in the treated eyes compared with baseline values; and uveoscleral outflow was increased (P<.005) by 56% in the treated eye. Peak pulse volume was unchanged. CONCLUSION. —Oxymetazoline reduces intraocular pressure by decreasing aqueous humor flow rates and increasing uveoscleral outflow. Oxymetazoline may have clinical potential as an ocular hypotensive drug.