Glaucoma Treatment: Eye Drops
and Other Medications
Glaucoma eye drops often are the first choice over glaucoma surgery and can be very effective at controlling IOP to prevent eye damage. If you are a good candidate for glaucoma eye drops, you may be prescribed more than one type to achieve the best IOP control. In fact, many types of these drops can enhance the effects of other types.
Depending on your general health and other medical conditions, however, you may be a poor candidate for glaucoma eye drops. This is because medications placed in the eye are absorbed into the conjunctival blood vessels on the eye's surface. A certain percentage of the active ingredient of the medication, though small, will enter the bloodstream and may adversely affect functions such as heart rate and breathing.
Likewise, some types of eye drops may worsen certain existing medical conditions such as asthma. Some glaucoma drugs also can interact with other common medications such as digitalis, prescribed for heart conditions. So make sure you discuss these issues with both your family physician and your eye doctor.
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Types of Glaucoma Eye Drops
Glaucoma eye drops are classified by the active ingredient chemical that helps make the drug work. Also, many of the glaucoma eye drops listed here are available in generic forms at your pharmacy.
Prostaglandins. Drugs known as prostaglandins used in eye drops often have the best user compliance because they are required only once daily. Prostaglandins generally work by relaxing muscles in the eye's interior structure to allow better outflow of fluids, thus reducing buildup of eye pressure.
These drugs have a few common side effects, including stinging and burning when put in the eye, eye color change (darkening of the eye) due to an increase of pigmentation in the iris, and lengthening and curling of the eyelashes. (In fact, the eyelash growth side effect eventually led to the development of an eyelash-lengthening drug called Latisse, which is available by prescription.)
FDA-approved prostaglandins include Xalatan (Pfizer), Lumigan (Allergan), Travatan Z (Alcon) and Rescula (Novartis). Many glaucoma specialists now report that prostaglandins have taken the lead in recent years as a first-line therapy for glaucoma (EyeWorld, January 2007).
Beta-blockers. Used in a variety of glaucoma eye drops, beta-blockers were at one time the drugs of first choice in treating glaucoma. These drugs work by decreasing fluid (aqueous) production in the eye and now are often prescribed as an adjunct to or in combination with prostaglandins.
These eye drops have the potential to reduce heart rate and may cause adverse side effects in individuals with certain heart problems, lung problems (such as emphysema), diabetes, depression or other conditions. For these reasons, make sure you discuss your medical history in detail with your eye doctor before using beta-blockers.
Various glaucoma eye drops are classified by the active ingredient chemical that helps make the drug work.
Examples of beta-blockers used in glaucoma treatment are Timoptic XE (Merck), Istalol (ISTA) and Betoptic S (Alcon).
Alpha-adrenergic agonists. These drugs work by decreasing rate of aqueous humor production and can be used alone or in combination with other anti-glaucoma eye drops.
Common side effects associated with this classification of eye drop include red or bloodshot eyes (ocular injection), upper lid elevation, an enlarged (dilated) pupil and itching. The FDA-approved drugs in this class include Iopidine (Alcon), Alphagan (Allergan). and Alphagan-P (Allergan).
Carbonic anhydrase inhibitors. These drugs work by decreasing rate of aqueous humor production. They are usually used in combination with other anti-glaucoma eye drops and not alone. This classification of drug is also used in oral form (pills). Common side effects experienced with this classification of eye drop include burning, a bitter taste, eyelid reactions and eye redness (ocular injection).
The FDA-approved eye drops in this class include Trusopt (Merck) and Azopt (Alcon). The systemic (pill) form of carbonic anhydrase inhibitors (CAI) are Diamox (Sigma), Neptazane (Wyeth-Ayerst) and Daranide (Merck, Sharp, & Dohme). About half of patients cannot tolerate oral CAIs due to their systemic side effects, which include fatigue, depression, loss of appetite, weight loss, loss of libido, kidney stones, metallic taste and tingling in fingers and toes (peripheral neuropathies).
Parasympathomimetics. These drugs work by increasing the outflow of aqueous humor from the eye. They are frequently used to control IOP in narrow-angle glaucoma. These eye drops cause the pupil to constrict, which assists in opening the narrowed or blocked angle where drainage occurs.
Common side effects experienced with these types of eye drops include brow ache, pupil constriction, burning, and reduced night vision. FDA-approved drugs in this class include pilocarpine, carbachol, echothiophate and demecarium.
Epinephrine. The epinephrine class of drugs has a dual effect on the eye. These drugs work by decreasing the rate of aqueous humor production and increasing the outflow of aqueous humor from the eye.
Common side effects experienced with this classification of eye drop include pigmented eye surface membrane (conjunctival) deposits, blocked tear ducts and heart palpitations with an increased heart rate. The FDA-approved drugs in this class include epinephrine and Allergan's Propine (dipivalyl epinephrine).
For convenience, two different types of glaucoma eye drops may be combined in one bottle.
Hyperosmotic agents. These drugs are usually for people with a severely high IOP that must be reduced immediately before permanent, irreversible damage occurs to the optic nerve. Hyperosmotic agents reduce IOP by lowering fluid volume in the eye.
Usually given only on a one-time, emergency basis, these drugs include oral glycerin and isosorbide orally, and mannitol and urea intravenously.
Combination glaucoma drugs. Study results show that half of individuals with glaucoma require more than one type of medication to control IOP.* For this reason, a few ophthalmic pharmaceutical companies have produced "combination" eye drops that can include two different anti-glaucoma medicines in the same bottle.
For convenience, your eye doctor might prescribe combined IOP-lowering medications. Typically, these combined medications have the additive effect of reducing IOP. Examples of FDA-approved medications of this type include Cosopt (Merck), Combigan (Allergan) and DuoTrav (Alcon).
Investigational Glaucoma Treatments
While some experimental glaucoma medications explore new ways of controlling IOP, other treatments are directed at protecting the optic nerve (neuroprotection) to prevent eye damage, potential vision loss or even blindness.
Many ongoing clinical studies are trying to find neuroprotective agents that might benefit the optic nerve and certain retinal cells in glaucoma. Many of these agents were developed from the results of work done on other central nervous system diseases such as Parkinson's and multiple sclerosis.
Some investigational treatments are undergoing FDA clinical trials to prove safety and effectiveness.
Other potential glaucoma treatments are strictly in experimental stages and may be years away from the possibility of being available on the marketplace.
Examples of neuroprotective agents under investigation for treatment of glaucoma include:
- Namenda (memantine). As of late 2010, Allergan had made no announcements regarding future plans for developing Namenda as a possible treatment for protecting the optic nerve from glaucoma damage. The drug underwent late-stage FDA clinical trials as a potential glaucoma treatment, but reportedly did not show significant benefit for patients.
Namenda originally was FDA-approved in 2003 for its neuroprotective effects in the treatment of Alzheimer's.
- Copaxone (glatiramer acetate). Copaxone is an injectable drug currently used to treat patients with multiple sclerosis. Developed by Teva Pharmaceuticals, the drug also is being investigated as a possible neuroprotective agent to prevent damage to the optic nerve from the effects of glaucoma. Copaxone appears to protect the optic nerve from the direct toxic effects on nerve cells caused by increased IOP.
- Gingko biloba. Some study results indicate that the herb gingko biloba might offer some protective effect for the optic nerve, which can be damaged by glaucoma. A small study reported in the February 2003 issue of Ophthalmology demonstrated that some individuals improved their ability to see a wider visual field following treatment with gingko biloba.
Other investigational treatments for glaucoma, aimed at controlling high IOP, include:
- Latanoprost Punctal Plug Delivery System. During earlier FDA clinical trials, this drug delivery system by QLT Inc. involved inserting a tiny punctal plug into a drainage channel in the eye. During a 12-week period, the drug slowly was released to control high intraocular pressure associated with glaucoma.
Early investigations originally showed the system might have potential as a drug delivery device. But at this time, the company is working on a different design to help improve results.
This drug delivery method possibly could address problems with compliance among people who must use eye drops daily.
- Nanoparticles. University of Central Florida researchers have reported promising results from experiments using laboratory-created nanoparticles to deliver a compound able to block enzymes that create carbon dioxide, which contributes to the buildup of internal eye pressure associated with glaucoma. Investigations into this approach to treating glaucoma are in very early stages.
*"Combination Drugs" presentation by Douglas J. Rhee, MD, of the Massachusetts Eye & Ear Infirmary, Boston, at the 2007 American Society of Cataract and Refractive Surgery conference in San Diego.
[Page updated January 2012]
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