These medicines can be applied to the eye (topical), given
in a pill form, or given through a needle into a vein (intravenous). Carbonic
anhydrase inhibitors have orange bottle caps. If you need to use more than one
type of eyedrop, you may need to take each medicine in a certain order. You can
use the color of the bottle cap to help you keep track of each type of
If you are using more than one type of eyedrop, wait 5
minutes between eyedrop medicines.
How It Works
Carbonic anhydrase inhibitors reduce how much fluid (aqueous humor) is
produced in the eye. Because the eye is making less fluid, this medicine can lower
the pressure inside the eye.
Why It Is Used
These medicines help lower the pressure in the eye. If you have lower pressure inside
your eye, your risk of damage to the optic nerve is lower, which can prevent
further vision loss.
The pill form of these medicines is used for
people whose glaucoma cannot be controlled by using eyedrops alone. The pill form may also be good for people who have not
been able to tolerate eyedrops.
Carbonic anhydrase inhibitors are sometimes
used in emergencies (in pill form or intravenously) to rapidly reduce the
pressure inside the eye in
How Well It Works
Carbonic anhydrase inhibitors can
lower eye pressure by 15% to 50%, depending on whether the medicine is in eyedrop form or pill form.1 The pill form works better, but it has more side effects.
All medicines have side effects. But many people don't feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.
Here are some important things to think about:
Usually the benefits of the medicine are more important than any minor side effects.
Side effects may go away after you take the medicine for a while.
If side effects still bother you and you wonder if you should keep taking the medicine, call your doctor. He or she may be able to lower your dose or change your medicine. Do not suddenly quit taking your medicine unless your doctor tells you to.
Call 911 or other emergency services right away if you have:
Swelling of your face, lips, tongue, or throat.
Call your doctor if you:
Have an allergic reaction in your eyes (redness, itching, tearing, swelling).
Feel unusually tired or weak.
Have blood in your urine.
Find it difficult or painful to urinate.
Have signs of low potassium levels in your body. These include:
Mood or mental changes.
Muscle cramps or pain.
Nausea or vomiting.
Common side effects of this medicine include:
Stinging, burning, blurring, or other discomfort in the eye.
Feeling the urge to urinate more often or having more urine than normal.
Loss of appetite or weight loss.
Bitter taste in your mouth.
Numbness, tingling, or burning in the hands and feet.
See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)
What To Think About
Carbonic anhydrase inhibitors can make severe kidney
disease, diabetes, COPD, gout, Addison's disease, liver disease, or kidney stones worse. If you have or have had any of these problems, let your eye doctor know before you begin
treatment with any of these medicines.
These medicines may lower your potassium levels. So your doctor may suggest that you get extra potassium in your diet or take a supplement.
Your doctor may suggest that you drink plenty of fluids while you take this medicine. This is to help prevent kidney stones. If you have kidney, heart, or liver disease and have to limit fluids, talk with your doctor before you increase the amount of fluids you drink.
Dorzolamide eyedrops may cause your eyes to become more sensitive to light. You may want to wear sunglasses or avoid bright light.
If you wear contact lenses, you may need to take your contacts out before you put this medicine in your eye. You can reinsert the contacts 15 minutes after using the eyedrops.
Your doctor may suggest Cosopt for you. This medicine has a carbonic anhydrase inhibitor (dorzolamide) and another type of glaucoma medicine (timolol) mixed into one bottle.
Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don't take your medicines properly, you may be putting your health (and perhaps your life) at risk.
There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed.
Advice for women
If you are pregnant, breast-feeding, or planning to get pregnant, do not use any medicines unless your doctor tells you to. Some medicines can harm your baby. This includes prescription and over-the-counter medicines, vitamins, herbs, and supplements. And make sure that all your doctors know that you are pregnant, breast-feeding, or planning to get pregnant.
Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.
Abramowicz M (2010). Drugs for some common eye disorders. Treatment Guidelines From The Medical Letter, 9(99): 1–8.
How this information was developed to help you make better health decisions.