|dorzolamide and timolol
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 remember when to use 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 decrease
the pressure in the eyes by reducing how much fluid (aqueous humor) is
produced in the eye.
Why It Is Used
Medicines taken by mouth (oral) are
sometimes used when eyedrops for
open-angle glaucoma have failed to keep the pressure
down inside the eyes.
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
reduce the amount of fluid made in the eyes by 40% to 60%.1 Because the eye is making less fluid, this medicine can lower
the pressure inside 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. These
medicines have frequent side effects that affect the rest of the body.
Side effects of dorzolamide and
brinzolamide include a stinging feeling in the eyes, blurred vision,
inflammation of the clear covering of the eyes (cornea), and allergic reactions
of the eyes. Dorzolamide and brinzolamide can occasionally cause total body
side effects, but because they are given as eyedrops, these side effects are
Side effects of carbonic anhydrase inhibitors that are
taken by mouth or given through a vein include:
- Bitter taste in the
- Tingling in the hands and feet.
(Many people who take the oral form of these medicines develop this side
- Decreased appetite and weight loss.
Low potassium levels in the body.
Depression and decreased sex drive (less
Anemia (very rare).
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 (in
pill form) can be used for long periods of time to treat people who have not
been able to tolerate eyedrops. They are also used when eyedrops alone have not
been effective in decreasing the pressure in the eyes.
medicines are very effective at reducing the pressure in the eyes. For this
reason, they are often used in emergency situations in which pressure inside
the eyes needs to be decreased rapidly to prevent vision loss.
Some people who start taking these medicines have to stop taking them
because of side effects. The pill or intravenous forms of these medicines are
more likely to cause side effects than the eyedrop forms of other
Carbonic anhydrase inhibitors can make severe kidney
disease, liver disease, or kidney stones worse. If you have had problems
affecting the kidneys or liver, let your eye doctor know before you begin
treatment with any of these medicines.
Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.
Salmon JF (2008). Glaucoma. In P Riordan-Eva, JP
Whitcher, eds., Vaughan and Asbury's General Ophthalmology, 17th ed., pp. 212-228. New York: