In vitro activity: Brimonidine reduces the progressive loss of ganglion cells to 26% and 15% at doses of 0.5 mg/kg and 1 mg/kg, respectively. Brimonidine administration initiates 10 days after IOP elevation prevents any further loss of ganglion cells. Brimonidine attenuates the increase in immunoreactivity of GFAP in ocular hypertensive retinas. Brimonidine, but not timolol, shows significant protection of retinal ganglion cells when applied at the time of intraocular pressure (IOP) elevation and prevents further cell loss when applied after intraocular pressure (IOP) is elevated. Brimonidine injected intravitreally into Sprague-Dawley rat eyes increases the number of BDNF-positive RGCs from 55% to 166%. Brimonidine 0.5% given as one drop before, after, or both before and after 360 degrees argon laser trabeculoplasty significantly lowers the incidence of postlaser IOP spikes. Brimonidine 0.2% instilled twice daily offers long-term IOP control comparable with that achieved with timolol 0.5% and better than betatolol 0.25% suspension.

Kinase Assay: [3H]Brimonidine (UK 14304) is a full agonist at alpha 2-adrenergic receptors. [3H]Brimonidine (UK 14304) labels at least 2 specific binding sites in human brain that both have the characteristics of an alpha 2-adrenergic binding site. GTP decreases agonist binding at both of these sites, but with different potencies at each site.