Published Sep 7, 2026
Dorzolamide is one type of eye drop medication that can be used to reduce high pressure within the eye. Chewy.com
Dorzolamide is an eye medication used to reduce abnormally high pressure within the eye. In this article, you’ll learn about how dorzolamide works, when it is prescribed, side effects to look for and other important information to know if dorzolamide has been prescribed for your kitty.
Dorzolamide for Cats
About Dorzolamide for Cats
In this photo, the cat’s left eye shows signs of glaucoma, or high pressure inside the eye. Anna Krivitskaya / Shutterstock.com
Dorzolamide is a topical eye medication used to treat high pressure within the eye. Pressure within the eye, which is called intraocular pressure (IOP) is highly dependent on the production and drainage of fluid within the eye.
The inside of the eye contains a fluid called aqueous humor. Aqueous humor flows through both the front and back chambers of the eye, providing nourishment to internal structures including the cornea and lens. This fluid is produced by a structure called the ciliary body, which is positioned near the lens in the back chamber of the eye.
After circulating, aqueous humor must also drain out of the eye. In cats, a majority of fluid drains at the iridocorneal angle, an area located around the entire eye, between the cornea and iris.
When pressure is increased inside the eye, this condition is called glaucoma. Glaucoma can happen for many reasons in cats including primary genetic factors or a number of secondary factors. Fortunately, glaucoma in cats tends to be rare, especially primary glaucoma. Secondary glaucoma causes are still uncommon but could occur in any cat with the top two being uveitis (inflammation in the eye) and a tumor inside the eye. Regardless of the cause, in a majority of glaucoma cases, something blocks the outflow of aqueous humor.
While the eye can normally make adjustments to aqueous humor production in response to some situations, significant blockages to outflow will lead to increased eye pressure as more and more aqueous humor is produced at a degree higher than it can drain from the eye.
There are a couple of medication types that can be used to treat glaucoma. Carbonic anhydrase inhibitors (CAI) like dorzolamide work by reducing the formation of hydrogen and bicarbonate ions. Preventing them from being available in secretions from the ciliary body ultimately decreases aqueous humor secretion.
Dorzolamide can be used on its own as a single medication to treat glaucoma in cats and has been shown in studies to effectively decrease intraocular pressure (IOP).
However, it is more common for a combination medication to be used where a CAI is combined with a beta blocker like timolol. This may reduce IOP only a little further, but combination products may be given less frequently and may be better tolerated by some cats. Studies have found that dorzolamide given three times a day had similar effect to the combination product Cosopt that contains both dorzolamide and timolol.
Timolol may also be another first line choice to treat glaucoma in cats. However, the impact on eye pressure may not be as strong and it is not appropriate for cats with certain types of other health conditions.
Dosing Information for Cats
It’s extremely important to follow your veterinarian’s instructions when using dorzolamide or a combination medication. How often to give them can vary and may change the amount that pressure in the eye is reduced.
Use of these medications must be based on checking eye pressure, which can only be done with your veterinarian. Make sure to always keep these recheck appointments in case adjustments in medication type or frequency is needed.
Only one drop of medication per dose into the affected eye is needed. There is no advantage to administering additional drops at one time. This medication’s influence on intraocular pressure is related more to the frequency at which it’s given.
Dorzolamide is most often used every 8 hours, however it has shown efficacy being given every 12 hours. Giving it every 8 hours may reduce the intraocular pressure further than every 12 hours administration but this may also not be practical for everyone. In these cases, if further reduction in pressure is needed, it may be necessary to add on a topical beta blocker like timolol or use a product like Cosopt, where the two medications are combined together.
When given initially for glaucoma, dorzolamide’s effects will start working on aqueous humor production in about 6 hours. However, according to studies, the overall cumulative impact on intraocular pressure may not occur until the first 3-5 days of administration.
How To Administer Dorzolamide to Cats
One of the best ways to administer eyedrops to a cat is to position them on the floor between your knees, facing away from you, hold their head with your non-dominant hand, tilt it back, use your thumb and middle finger (of your dominant hand) to open the eye and squeeze the bottle gently with your thumb and index finger of your dominant hand. This prevents your kitty from backing up on you or being scared of something coming directly at their face. You can also add a basic towel wrap if they interfere with their front paws. Chris Vanderhoof / Cats.com
Dorzolamide comes only in a topical eye drop form. Oral/systemic forms of carbonic anhydrase inhibitors are not recommended for cats as they are more sensitive to their side effects.
With your cat sitting on your lap facing away from you, gently tilt their head up so you can clearly see the eye. An alternative position is to squat in a kneeling position with your kitty positioned between your legs. This position is more effective to keep your cat from backing up on you.
Keeping gentle leverage under the chin, use your thumb to raise the upper lid and your pointer finger to lower the bottom lid. With your other hand, apply the drop to the surface of the eye by gently squeezing the bottle.
Do not let the bottle touch the eye. Allow the liquid to squeeze out of the bottle and land on the eye surface. After applying, your cat will blink immediately. When your cat blinks, this will help to spread out the medication.
Administering an ointment prior to a liquid solution will prevent the liquid solution from reaching the surface of the eye. So make sure if your cat also has any ointment medication, that dorzolamide is administered first. If you do have any other eye medications you’re giving your cat, they can be given around the same time. However, it’s best to wait 5 minutes after applying one medication before applying another.
Administration Tips
- Try to avoid administering eye medication facing your cat. Your cat is more likely to back up away from you.
- Try to apply eye medication when your cat is relaxed.
- Provide your cat with a treat reward or meal after applying eye medication.
- Wrapping your cat in a towel or blanket can help give your cat a sense of security and keep them from moving or swatting your hand away.
- It may also be easier to have someone else help you. Let them hold your cat securely while you gently open the eye and apply the medication.
Side Effects of Dorzolamide for Cats
Rechecks with your primary care vet or veterinary ophthalmologist are extremely important for monitoring eye pressures while on dorzolamide as well as any side effect concerns. Beatriz Vera / Shutterstock.com
Dorzolamide’s main side effect is that it can cause a burning or stinging sensation when applied. This is due to its low pH. If this is a concern for your cat, another similar medication called brinzolamide may be an option, which may reportedly sting less but has similar efficacy to dorzolamide.
While systemic body-wide effects with this topical medication are not common, a condition called renal tubular acidosis and low levels of blood potassium have been reported. This may be more likely in cats with chronic use. Your veterinarian may advise routine bloodwork if your cat is on this medication to monitor kidney function and blood potassium levels.
Keratitis (corneal inflammation) is a side effect described in dogs with long-term administration of dorzolamide. This may be possible in cats though is not as well documented.
Dorzolamide is chemically similar to sulfonamide medications. It should not be used in cats with a known sulfa allergy. Human caretakers with sulfa allergies should also be very cautious when administering to their cat. Wearing gloves to administer would be a good precaution.
Overdose and Emergencies
While still very rare, the most common emergency related to dorzolamide administration would be a cat hypersensitive to the medication having a reaction after administration. There is unfortunately no way to predict these occurrences though thankfully, they are rare.
If your cat develops eye inflammation or irritation after administration of dorzolamide, it may be helpful to first flush the eye with an artificial tears solution (such as GenTeal tears or Refresh).
After flushing the eye(s), make sure to immediately contact one or more of the following for advice:
- Your veterinarian
- ASPCA Animal Poison Control Center (1-888-426-4435)
- Pet Poison Helpline (1-855-764-7661)
Potential Drug Interactions With Dorzolamide
The following list represents potential drug interactions with dorzolamide. Unless specifically noted, use together is not necessarily contraindicated but use together should be considered carefully with veterinary guidance.
- Oral carbonic anhydrase inhibitors (acetazolamide, zonisamide): may increase risk for additive effects. Zonisamide is related to other CAIs and may be used as an anticonvulsant for seizures in cats. It does not have an impact on intraocular pressure and has a different side effects profile but should be used carefully if a topical CAI is being used or added. Otherwise, oral carbonic anhydrase inhibitors are not recommended for use in cats as a way of reducing intraocular pressure due to their side effect risk. There is no advantage to using an oral CAI on top of a topical eye medication form.
- Potassium-depleting drugs (prednisolone, diuretics like furosemide): may worsen any associated low blood potassium from dorzolamide use.
- Salicylates (aspirin, Pepto-Bismol): use together with high dose salicylate therapy may increase the risk for electrolyte disturbances and related side effects. High doses of aspirin or Pepto-Bismol are not considered safe for cats anyway and should not be used.
How to Store Dorzolamide
Dorzolamide ophthalmic solution should be stored at room temperature (68-77 degrees F) and kept protected from light.
Do not directly mix or store with any other ophthalmic medications.
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