Dexmedetomidine-induced ocular hypotension in rabbits with normal or elevated intraocular pressures

This study covered the ocular hypotensive effects of the stereoisomers of the alpha 2-adrenoceptor agonist medetomidine. The dextro-isomer, dexmedetomidine, is known from pharmacologic experiments to be a specific, potent, and selective full agonist at alpha 2-adrenoceptors, whereas the levo-enantiomer seems to be almost inactive. Thus, the levo-isomer (0.5 mg/ml, 25 microliters) had no significant effect on intraocular pressure. After unilateral topical administration, dexmedetomidine (0.5 mg/ml, 25 microliters) lowered intraocular pressure bilaterally in normal rabbits and in rabbits with intraocular pressure elevated after laser irradiation of the pigmented trabecular band of the anterior chamber angle. In the treated (ipsilateral) eye of normal rabbits, a maximum decrease of 4.6 +/- 0.6 mmHg was observed at 2 hr post treatment. In the contralateral eye, the maximum decrease was 4.1 +/- 0.5 mmHg at 1 hr after treatment. In rabbits with laser-induced elevation of intraocular pressure, the maximum decrease in treated hypertensive eyes was 13.5 +/- 0.3 mmHg 1 hr after dexmedetomidine administration. These results indicate that the selective alpha 2-adrenoceptor agonist, dexmedetomidine, is a potent and effective drug for decreasing intraocular pressure in rabbits.