The influence of clonidine on intraocular pressure.

In order to study the influence of clonidine on intraocular pressure (IOP), the drug was administered via different routes. The experiments were performed on chloralose-anaesthetized cats. The rise in IOP observed after administration of clonidine into the external carotid arteries was subjected to a pharmacological analysis. Our experiments suggest that the increase in IOP is due to the contraction of eyelids and extraocular muscles, mediated by the influence of clonidine on alpha-adrenoceptors. The IOP-lowering effect of clonidine was more pronounced after its infusion into the left vertebral artery than after its intravenous injection. This difference would suggest that the clonidine-induced decrease in IOP may be mediated via a central mechanism.