Topical nylidrin and aqueous humor dynamics in rabbits and monkeys

Topical administration of nylidrin hydrochloride lowered intraocular pressure in both albino rabbits and cynomologus monkeys. The maximum decrease occurred two hours following drug application and was unilateral. The response lasted four hours in monkeys and at least six hours in rabbits. Outflow facility, episcleral venous pressure, and aqueous humor flow measured by fluorophotometry were unaltered in both species. In rabbits in the treated eyes, ocular blood flow was increased, and anterior and posterior chamber ascorbate concentrations were unchanged. The mechanism of IOP reduction appears to be increased aqueous humor outflow via uveoscleral outflow routes that are not pressure dependent.