The influence of clonidine on intraocular pressure after topical application to the eyes of anesthetized cats.

Clonidine was topically applied to the right eye of anesthetized cats. Unilateral administration induced a fall in intraocular pressure (IOP) in both eyes. This effect is not secondary to the slight fall in arterial blood pressure. Distribution experiments with 14C-clonidine revealed that only minor or negligible amounts of clonidine could be demonstrated in the contralateral eye. The concentrations of the labeled drug determined in the brain after topical application are sufficient to explain the bilateral decrease in IOP by a central mechanism. The IOP-lowering effect of clonidine upon its topical application to the eye is probably of central nervous origin and, therefore, similar to the centrally induced effect on IOP after systemic administration of the drug.