How Do Antiglaucoma Prostaglandin Agonists Work?

Antiglaucoma prostaglandin agonists reduce pressure inside the eye (intraocular pressure) by increasing the outflow of aqueous humor in the eye. Prostaglandin agonists or analogs enhance the activity of prostaglandin, a type of hormone which plays a role in regulating the outflow of aqueous humor in the eye.

Aqueous humor is a transparent, watery fluid that fills the two chambers (anterior and posterior) between the lens and the cornea in the eyes. Aqueous humor supplies oxygen and nutrients to the lens and cornea and removes waste products, while also allowing light to pass through.

A part of the eye known as the ciliary body secretes aqueous humor into the posterior chamber, which passes through the pupil, fills and drains out of the anterior chamber. Aqueous humor drains out of the eyes into the ocular veins through two pathways:

• Trabecular meshwork: Trabecular meshwork is specialized porous tissue in the eyes that enables drainage.
• Uveoscleral pathway: Uvea and sclera are layers in the eyes through which part of the aqueous humor seeps through.

Balancing the inflow and outflow of aqueous humor is necessary to maintain optimum pressure in the eye and the eye’s spherical shape. Prostaglandins increase aqueous humor outflow through both the pathways in two ways:

• Relax the ciliary muscle which increases the space between the muscle fiber bundles to allow outflow.
• Degrade collagen in the extracellular matrix to widen the space between the cells. Extracellular matrix is a network of collagen and other proteins which provide structural support to cells to adhere and form tissue.

Most antiglaucoma prostaglandin agonist medications are solutions or emulsions which are topically administered in the eye. One of the medications is a biodegradable implant placed inside the eye’s anterior chamber, which slowly releases medication, designed to last up to 6 months.

Antiglaucoma prostaglandin agonists are most often used as first-line therapy to reduce intraocular pressure, because of their efficacy, once-daily dosing and minimal systemic side-effect profile. Antiglaucoma prostaglandin agonists are used to treat the following eye conditions:

• Open-angle glaucoma: Glaucoma is a degenerative disease that damages the optic nerve and can lead to vision loss if left untreated. Open-angle glaucoma is the most common type of glaucoma in which the drainage angle through which the aqueous humor drains remains open, but the drainage channels are partially blocked.
• Ocular hypertension: Elevated intraocular pressure due to imbalance in the production and drainage of aqueous humor.
• Hypotrichosis of the eyelashes: A rare condition with little or no growth of eyelashes. Prostaglandin stimulates the hair follicle growth and is applied to the eyelid margins at the base of the eyelashes.

Side effects of antiglaucoma prostaglandin agonists may include the following:

Ocular symptoms:

• Conjunctival hyperemia (dilation of blood vessels in the conjunctiva, the membrane that lines the eye and inner surface of eyelids)
• Thickening, lengthening, growth and pigmentation of eyelashes
• Pain, burning and stinging
• Irritation, discomfort and foreign body sensation
• Itching (pruritus)
• Inflammation of conjunctiva in a pinpoint pattern (punctate conjunctivitis)
• Conjunctival edema
• Conjunctival hemorrhage
• Dry eyes
• Eye strain and fatigue
• Visual disturbances
• Blurred vision
• Decreased vision acuity
• Double vision (diplopia)
• Pigmentation of iris
• Intraocular inflammation (iritis or uveitis)
• Iris adhesions or cysts
• Increased intraocular pressure
• Pigmentation of the skin around the eye
• Redness around the eyes
• Rash and itching around the eyes
• Blepharitis (inflammation of the eyelids)
• Cataract
• Inflammation of the cornea (punctate keratitis)
• Corneal damage
• Corneal edema
• Degeneration of cornea in a pinpoint pattern (punctate keratopathy)
• Eyelid redness, pain and burning sensation
• Eyelid edema and swelling
• Eyelid itching and irritation
• Eyelid margin crusting
• Changes in the eyelid fold (sulcus)
• Tearing and/or discharge
• Light sensitivity
• Macular edema (swelling in the macula, the central portion of the retina)
• Cystoid macular edema (thickening of macula)
• Hypersensitivity reactions
• Abnormal growth of eyelashes (trichiasis)
• Retinal artery block
• Vitreous (gel-like fluid fills the eyeball space between the lens and the retina) hemorrhage in people with diabetic retinopathy
• Pseudopemphigoid (scar tissue formation) of the ocular conjunctiva

Additional side effects specific to ophthalmic prostaglandin implant:

• Leakage of aqueous humor
• Corneal touch
• Anterior chamber inflammation
• Anterior chamber flare (an optical phenomenon)
• Pooling of blood in the anterior chamber (hyphema)
• Inflammation of iris and ciliary body (iridocyclitis)
• Corneal opacity

Systemic side effects:

• Headache
• Dizziness
• Asthma-like symptoms
• Shortness of breath (dyspnea)
• Hypersensitivity reactions such as rashes or allergic dermatitis
• High blood pressure (hypertension)
• Nausea
• Upper respiratory infection, cold, flu
• Chest pain (angina) and palpitations
• Muscle, bone or joint pain

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 prostaglandin agonists include:

• Bimatoprost (Latisse, Lumigan)
• Bimatoprost ophthalmic implant (Durysta)
• Latanoprost (Xalatan, Xelpros)
• Latanoprostene bunod ophthalmic (Vyzulta)
• Travoprost ophthalmic (Travatan, Travatan Z)
• Tafluprost (Zioptan)
• Omidenepag isopropyl ophthalmic (new drug pending FDA approval)