Brimonidine (bri-MOE-ni-deen) is a drug used as eye drops under the brand names Alphagan and Alphagan-P to treat open-angle glaucoma or ocular hypertension, and as a gel, Mirvaso, for rosacea (facial erythema).
It acts via decreasing synthesis of aqueous humor, and increasing the amount that drains from the eye through uveoscleral outflow. In treating erythema, it acts by vasoconstriction (narrowing of blood vessels).
Clinical uses
Brimonidine is indicated for the lowering of intraocular pressure in patients with open-angle glaucoma or ocular hypertension. It is also the active ingredient of Combigan along with timolol maleate.
A Cochrane Systematic Review compared the effect of brimonidine and timolol in slowing the progression of open angle glaucoma in adult participants.
In 2013, the FDA approved topical application of brimonidine 0.33% (Mirvaso) for facial erythema or rosacea.
Mechanism of action
Brimonidine is an α2 adrenergic agonist.
Alpha 2 agonists, through the activation of a G protein-coupled receptor, inhibit the activity of adenylate cyclase. This reduces cAMP and hence aqueous humour production by the ciliary body.
Peripheral alpha 2 agonist activity results in vasoconstriction of blood vessels (as opposed to central alpha 2 agonist activity that decreases sympathetic tone, as can be seen by the medication clonidine). This vasoconstriction may explain the acute reduction in aqueous humor flow. The increased uveoscleral outflow from prolonged use may be explained by increased prostaglandin release due to alpha adrenergic stimulation. This may lead to relaxed ciliary muscle and increased uveoscleral outflow.
References
- Mosby's Drug Guide for Nurses (7th edition; Skidmore) 2007.
External links
- Alphagan P product website
- Alphagan P prescribing information