REVIEW Brimonidine is an alpha adrenergic receptor agonist (primarily alpha-2). It has a peak ocular hypotensive effect occurring at two hours post-dosing. Fluorophotometric studies in animals and humans suggest that Brimonidine has a dual mechanism of action by reducing aqueous humor production and increasing uveoscleral outflow.
Toris, C.; Camras, C.; Yablonski, M. (1999). Acute versus chronic effects of brimonidine on aqueous humor dynamics in ocular hypertensive patients. American journal of ophthalmology 128 (1): 8-14. PMID 10482088.