How Do Antiglaucoma Alpha Agonists Work?

Antiglaucoma alpha agonists are medications that reduce the pressure inside the eye (intraocular pressure). Antiglaucoma alpha agonists decrease production of aqueous humor in the eye and improve its drainage. Aqueous humor is a clear fluid that forms and fills the posterior and anterior chambers of the eye which are located between the lens and the cornea.

A part of the eye known as the ciliary body produces aqueous humor, which supplies nutrients to the lens and cornea and removes waste products. Aqueous humor inflow and outflow are a continuous process which maintains an optimum pressure in the eye, and the eye's spherical shape.

Aqueous humor drains back into veins in the eyes through two pathways:

• Trabecular meshwork: Specialized porous tissue that allows aqueous humor to drain through a channel known as Schlemm’s canal, and is known as the conventional pathway.
• Uveoscleral pathway: The aqueous humor seeps through tissues in the uvea and sclera, which are layers in the eye, and drains into the veins. This pathway is known as the unconventional pathway, because there is no defined structure for this outflow.

A proper balance in the inflow and outflow of aqueous humor is essential to maintain normal intraocular pressure. Antiglaucoma alpha agonists reduce intraocular pressure by decreasing the production of aqueous humor by the ciliary body and increasing drainage through the uveoscleral pathway.

Antiglaucoma alpha agonists also constrict tiny blood vessels on the surface of the eyeball and reduce redness of the eye.

Antiglaucoma alpha agonists are ophthalmic solutions administered in the eyes. Antiglaucoma alpha agonists are used in the following situations:

• To reduce elevated intraocular pressure in patients with open-angle glaucoma, a disease that damages the optic nerve and can lead to vision loss if left untreated.
• To prevent an increase in intraocular pressure after laser eye surgery.
• To reduce eye redness from irritation.
• To treat anterior ischemic optic neuropathy (damage to optic nerves due to reduced blood flow).
• To treat ocular graft-versus-host disease after a corneal transplant, in which the donor cells attack the recipient’s healthy eye tissue.

Side effects of antiglaucoma alpha agonists may include the following:

• Ocular side effects
• Conjunctival hyperemia (dilation of blood vessels in the conjunctiva, the membrane that lines the eye and inner surface of eyelids)
• Allergic conjunctivitis (allergic inflammation of the conjunctiva)
• Eye pain
• Eye itching and discomfort
• Eye tearing and discharge
• Blepharitis (inflammation of the eyelids)
• Blurred vision
• Eye edema
• Dry eye
• Damage to cornea (keratopathy)
• Corneal inflammation (keratitis)
• Eyelid problems such as redness, crusting and retraction
• Sensitivity to light

Non-ocular side effects

• Dry mouth
• Dry nose
• Rash
• Headache
• Fatigue and weakness
• Dizziness
• Dyspepsia (indigestion)
• Nausea
• Constipation
• Irregular heartbeat (arrhythmia)
• Abnormal coordination
• Abnormal skin sensation
• Contact dermatitis
• Insomnia
• Depression
• Distortion in smell and taste
• Drowsiness
• Nervousness
• Peripheral edema
• Muscular pain (myalgia)
• Asthma
• Chest pain
• Shortness of breath (dyspnea)
• Pharyngitis (inflammation of the pharynx)
• Rhinitis (inflammation of mucous membrane in the nose

The information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of some antiglaucoma alpha agonists include:

• Brimonidine (Alphagan P, Qoliana, Lumify)
• Apraclonidine, lopidine

Brimonidine is the primary antiglaucoma alpha agonist used to treat glaucoma. Apraclonidine is mainly used to control the rise in intraocular pressure immediately after laser eye surgery, because of its high incidence of adverse reactions and diminishing effectiveness (tachyphylaxis) with use. Most of the non-ocular side effects listed above are caused by apraclonidine.