Nearly all glaucoma medications are prescribed to reduce eye pressure. They generally work by reducing the production of aqueous humor and increasing fluid outflow (drainage). In most cases, these drugs are taken as eye drops. If drops alone do not work, your doctor may also prescribe an oral medication (pill).
Prostaglandins are hormone-like substances that help widen blood vessels. Drugs that mimic natural prostaglandins increase the drainage of aqueous humor to help reduce intraocular pressure. Prostaglandin-like drugs are the first-line treatment for glaucoma.
Latanoprost (Xalatan, generic) is the standard brand. Latanoprost was the first prostaglandin to be approved as first-line treatment for elevated eye pressure. Three newer prostaglandins are travoprost (Travatan), bimatoprost (Lumigan),and tafluprost (Zioptan). These drugs are used to reduce eye pressure in patients with open-angle glaucoma and high ocular pressure.
Side effects include itching, burning, and eye redness. All of these drugs may permanently change eye color from blue or green to brown.
Topical beta-blockers lower the pressure inside the eye by inhibiting the production of aqueous humor.
Timolol (Timoptic, Betimol, generic) is the standard brand. Other examples of beta-blockers used for glaucoma treatment are levobunolol (Betagan, generic), carteolol (Ocupress, generic), metipranolol (OptiPranolol, generic), and betaxolol (Betoptic, generic).
After a beta-blocker is administered, only a tiny amount of the drug is absorbed by the cornea. Most of it enters in the bloodstream. These drugs, therefore, can cause side effects in parts of the body other than the eyes ("systemic" side effects). Beta-blockers may:
- Cause reduced sexual drive, fatigue, depression, anxiety, and breathing difficulties.
- Lower heart rate and reduce blood pressure.
- Worsen severe asthma or other lung diseases.
- Cause a sudden rise in eye pressure, particularly if a patient has switched to a beta-blocker from another type of glaucoma medication. It is important that IOP be checked shortly after the other drug has been withdrawn.
- When beta-blockers are used to treat one eye, the other (contralateral) eye also experiences a lesser, but still significant reduction in IOP.
Topical beta-blockers can interact with oral medications, such as other beta-blockers, calcium-channel blockers, or the antiarrhythmic drug quinidine. People with diabetes who take insulin or hypoglycemic medications should be aware that beta-blocker side effects may mask the symptoms of hypoglycemia (low blood sugar).
Carbonic Anhydrase Inhibitors
Carbonic anhydrase inhibitors (CAIs) are used for glaucoma when other drugs do not work. They may be combined with other medications.
In addition to reducing aqueous humor production, CAIs may improve blood flow in the retina and optic nerve (beta-blockers do not). Improving blood flow can keep the disease from getting worse.
CAIs are available in the following forms:
- Eye-drop CAIs include dorzolamide (Trusopt, generic) and brinzolamide (Azopt). Side effects may include stinging in the eye, watery or dry eyes, or bitter taste. Brinzolamide is a newer medication that may cause less stinging than dorzolamide.
- Oral forms include acetazolamide (Diamox, generic) and methazolamide (Neptazane, generic). Although pill forms are more effective than eye drops, they have significantly more side effects and are rarely used for long-term treatment. Unpleasant side effects include frequent urination, stomach problems, and tingling in fingers and toes. People who are allergic to sulfa drugs or who have a history of kidney stones should not use these drugs. CAIs can also produce a toxic reaction when taken with large doses of aspirin.
Alpha agonists, also called adrenergic agonists, reduce the production of aqueous humor and increase drainage. They include apraclonidine (Iopidine, generic), brimonidine (Alphagan, generic), and dipivefrin (Propine).
The most common side effects are dry mouth, nose, and eyes, and blurred vision. Alpha agonists may also trigger an allergic reaction that causes red and itching eyes and lids.
Miotics, also called cholinergic agonists, narrow the iris muscles and constrict the pupil. This action pulls the iris away from the trabecular meshwork and allows the aqueous humor to flow out through the drainage channels, reducing the pressure inside the front of the eye.
Pilocarpine (Isoptocarpine, other brands, generic) was the most widely used anti-glaucoma drug before timolol was introduced. It is the preferred miotic. However, it has to be taken several times a day and many people have difficulty complying with this regimen. Carbachol (Isopto) is another miotic.
Miotics narrow the pupil and so decrease the amount of light that can enter the eye. This can cause dim vision and night blindness. Patients who take miotics often complain of difficulty seeing in darkened rooms or driving at night. Patients who have cataracts in addition to glaucoma may have particular problems with worsened vision.
Managing Drug Regimens
Many patients skip doses of their glaucoma medications, sometimes because of side effects and sometimes because of confusing or time-consuming regimens. Skipping even a few doses can greatly increase the risk of visual loss. It is essential that you inform your doctor if you are not regularly taking your medication. Otherwise, your doctor may increase the dosage, thereby causing unwelcome side effects.
Patients who do not regularly take their glaucoma medication are at high risk for blindness. If you have problems taking your medications or sticking to the dosing regimen, talk with your doctor.
Hints for Managing a Regimen.
- Pharmaceutical manufacturers use colored tops, yellow for timolol, for example, and green for pilocarpine, to help prevent mix-ups. Creating a chart scheduling each drug by color can be helpful.
- Small electronic timers are available that will signal times for taking the medications. The timing of these combinations is important.
- Some patients may be candidates for single medications that combine two drugs, such as Cosopt, which contains both dorzolamide and timolol. This medication requires only one drop twice per day. Patients who need additional glaucoma drugs, however, will need to take these two drugs separately.
- When using any drug for a long period of time, side effects are a potential problem. If they become severe, ask your doctor about reducing the dosage or trying other drugs.
Administering Eye Drops. A common reason that glaucoma medicine does not work is that patients do not take it correctly. Patients should ask the ophthalmologist to watch while they place the drops in their own eyes to make sure they are doing it correctly. The following are some recommended steps:
- If you use both ointments and eye drops, take the eye drops first.
- Wash your hands before applying eye drops.
- Hold the bottle upside down.
- Tilt your head back and, with one hand, pull the lower eyelid down to form a pocket.
- With your other hand, hold the bottle as close as possible to your eye. Don’t let the bottle directly touch your eye or eyelid.
- After you have placed the drop, close your eye or press your index finger against the corner of the eye near your nose. Gently move the lower lid upward until the eye is closed. Keep your eye closed for at least 1 minute. This prevents the drop from draining out.
- Wait at least 5 minutes before applying another drop or a different medication
Drug Therapy for Acute Closed-Angle Glaucoma
Acute closed-angle glaucoma is an emergency situation. Doctors may administer a combination of two or more medications to reduce eye pressure quickly before it can damage the optic nerve and cause visual loss. Apraclonidine (Iopidine, generic) is a powerful drug used before and after laser surgery to prevent an increase in fluid pressure and is more effective than other medications. In addition to standard drugs, doctors may also administer glycerin by mouth or mannitol or acetazolamide intravenously. Surgery is almost always performed once the pressure is reduced.