<p>Brimonidine tartrate is a relatively selective alpha-2 adrenergic receptor agonist that, in radioligand binding assays and in functional assays, is approximately 1000 times more selective for the alpha-2 adrenoceptor than the alpha-1 adrenoceptor. This selectivity results in the absence of vasoconstriction in microvessels associated with human retinal xenografts.<br />
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Topical administration of brimonidine decreases IOP in humans. When used as directed, brimonidine tartrate ophthalmic solutions reduce elevated IOP with minimal effect on cardiovascular parameters.<br />
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Brimonidine tartrate has a rapid onset of action, with the peak ocular hypotensive effect occurring at approximately two hours post-dosing. The duration of effect is 12 hours or greater.<br />
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Fluorophotometric studies in animals and humans suggest that brimonidine tartrate has a dual mechanism of action. Brimonidine Tartrate ophthalmic solution 0.15% lowers IOP by reducing aqueous humor production and increasing uveoscleral outflow.</p>