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Methazolamide for Dogs: A Medication to Manage Glaucoma

Catherine Barnette, DVMGhanasyam Bey, DVM
Published on July 15, 2024

Key takeaways:

  • Methazolamide (Neptazane) is a medication that’s used to treat glaucoma in dogs. Since it’s labeled for use in humans, its use in dogs is considered off-label. 

  • Common side effects of methazolamide in dogs include lack of appetite, vomiting, and diarrhea.

  • Methazolamide comes in tablet form and is typically given to dogs every 12 hours. Your veterinarian will determine the correct dosage of methazolamide for your dog.

A veterinarian is checking a dog's eyes for glaucoma.
Alexandr Lebedko/iStock via Getty Images Plus

Like humans, dogs can get the eye condition glaucoma. In addition to being painful, glaucoma, or increased eye pressure, can cause blindness

There are several medications used to treat glaucoma in dogs. One option is the oral medication methazolamide (Neptazane). If your dog is prescribed methazolamide for glaucoma, here’s important information you need to know.

Methazolamide for dogs at a glance

Common names

Methazolamide (Neptazane)

What it treats

Glaucoma

How it comes (forms)

Tablets

Common side effects

Decreased appetite, nausea, vomiting, diarrhea, and electrolyte abnormalities

Average cost

$30-$80 for 30 tablets

What is methazolamide, and what is used for in dogs?

Methazolamide belongs to a class of medications called carbonic anhydrase inhibitors. These medications block the activity of an enzyme (carbonic anhydrase) in the body. 

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Methazolamide has three main effects: 

  1. Decreasing fluid production in the eye

  2. Decreasing pressure within the skull

  3. Eliminating excess fluid from the body 

Thanks to these effects, methazolamide is used to treat glaucoma in dogs.

Less commonly, methazolamide is used to treat elevated intracranial pressure (pressure inside the skull). Increased intracranial pressure may be caused by: 

How is methazolamide given to dogs?

Methazolamide comes in tablet form and is usually given to dogs twice a day (every 12 hours). Your veterinarian will determine the best methazolamide dosage for your dog based on their weight and the condition being treated. 

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Methazolamide can be given to dogs with or without food. Giving your dog methazolamide with a meal may decrease the risk of gastrointestinal side effects.

Like many medications used in veterinary medicine, methazolamide is labeled for use in humans. So its use in dogs is considered off-label. Although methazolamide is only FDA approved for use in humans, studies have shown that it’s safe and effective for dogs.

What are the common side effects of methazolamide in dogs?

The most common side effects associated with methazolamide in dogs are: 

  • Decreased appetite

  • Nausea

  • Vomiting

  • Diarrhea

  • Electrolyte abnormalities

Though less common, some dogs may experience lethargy or drowsiness while taking methazolamide. 

If your dog experiences side effects from methazolamide, contact your veterinarian. They may recommend adjusting your dog’s dosage or switching to a different medication. One option is giving your dog eye drops instead of oral medication. Eye drops often have fewer side effects than oral medications because they remain in and around the eye. 

What are the most serious risks of methazolamide for dogs?

Although serious side effects from methazolamide are uncommon, they can occur. Potential serious side effects of methazolamide for dogs include: 

  • Kidney dysfunction

  • Liver dysfunction

  • Skin reactions

  • Allergic reactions

Your veterinarian may order blood tests to check your dog’s liver and kidney health before prescribing them methazolamide. If your dog has liver or kidney disease, your veterinarian may recommend avoiding methazolamide and using a different treatment. 

Your veterinarian may also order regular blood tests while your dog is taking methazolamide. This will help them diagnose and treat any liver or kidney effects early. 

If your dog experiences any serious side effects while taking methazolamide, stop giving them the medication and contact your veterinarian.

Does methazolamide interact with any other dog medications?

Methazolamide can interact with corticosteroids, such as prednisone or dexamethasone. This interaction can increase the risk of abnormal electrolyte levels in the body.

Methazolamide can also interact with eye drops that treat glaucoma. Do not combine glaucoma medications unless you are advised to do so by your veterinarian. 

Finally, be sure your veterinarian knows about any other medications your dog is taking. This includes prescription medications, over-the-counter medications, and supplements. With this information, your veterinarian can make the best recommendations for your dog. 

What should you do if your dog misses a dose of methazolamide?

If you forget to give your dog a dose of methazolamide, give them the missed dose as soon as possible. If it’s almost time for their next dose, skip the missed one and resume their normal medication schedule. Do not give your dog multiple doses of methazolamide at one time. 

The bottom line

Methazolamide (Neptazane) is an oral carbonic anhydrase inhibitor that’s used to treat glaucoma in dogs. Although oral glaucoma medications typically have more side effects than the eye drops, they can be effective. Talk to your veterinarian to determine the best glaucoma treatment for your dog. By working closely with your veterinarian, you can balance the benefits of a treatment against the potential risk of side effects. 

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Why trust our experts?

Catherine Barnette, DVM
Catherine Barnette, DVM, is a small animal veterinarian with 14 years of experience providing preventive care, medical workups, and surgical services in a number of general veterinary practices. She also served on her county's board of health for several years and taught biology laboratories for college students.
Renée Fabian, MA
Renée Fabian is the senior pet health editor at GoodRx. She’s worked for nearly 10 years as a journalist and editor across a wide range of health and well-being topics.
Ghanasyam Bey, DVM
Reviewed by:
Ghanasyam Bey, DVM
Ghanasyam Bey, DVM, is from Cleveland, Ohio, and attended Princeton University for undergraduate studies. After a year of biology research at Duke University, he attended Ohio State College of Veterinary Medicine.

References

Armour, M. (2015). Your treatment options for glaucoma in small animals. DVM360

Cornell Richard P. Riney Canine Health Center. (n.d.). Glaucoma

View All References (2)

Fingeroth, J. (2023). Traumatic brain injury in dogs and cats. Veterinary Partner. 

North Carolina State Veterinary Hospital. (n.d.). Neurology: Encephalitis in dogs and cats.

GoodRx Health has strict sourcing policies and relies on primary sources such as medical organizations, governmental agencies, academic institutions, and peer-reviewed scientific journals. Learn more about how we ensure our content is accurate, thorough, and unbiased by reading our editorial guidelines.

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