Brimonidine
Encyclopedia
Brimonidine is a drug
Medication
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...

 used to treat open-angle glaucoma
Glaucoma
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...

 or ocular hypertension
Ocular hypertension
Ocular hypertension is intraocular pressure higher than normal in the absence of optic nerve damage or visual field loss.Current consensus in ophthalmology defines normal introcular pressure as that between 10 mmHg and 21 mmHg...

.

It acts via decreasing synthesis of aqueous humor, and increasing the amount that drains from the eye through uveoscleral outflow.
As a treatment for glaucoma, it is usually given in eyedrop form.

Brimonidine is an α2-adrenergic receptor agonist.

Alpha 2 agonists, through the activation of the Gi GPCR, inhibit the activity of adenylate cyclase
Adenylate cyclase
Adenylate cyclase is part of the G protein signalling cascade, which transmits chemical signals from outside the cell across the membrane to the inside of the cell ....

. 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 adreneric stimulation. This may lead to relaxed ciliary muscle and increased uveoscleral outflow

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
Combigan
Combigan is a brand of eye drops indicated in the treatment of glaucoma. It is a combination of brimonidine and timolol, in concentrations of 0.2% and 0.5% respectively. Combigan is marketed and sold by Allergan....

 along with timolol maleate.

External links

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