What is methazolamide?
Methazolamide (brand names Neptazane®, GlaucTabs®, Glaumetax®, MZM) is a carbonic anhydrase inhibitor used off label (extra label) to treat open angle glaucoma in dogs and cats.
Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.
Methazolamide has been replaced, in many cases, with topical medications that have fewer systemic side effects.
How is methazolamide given?
- Methazolamide is given by mouth in the form of a tablet. It may also be compounded into a liquid form; measure liquid doses carefully.
- It may be given with or without food.
- If vomiting occurs when dosed on an empty stomach, give future doses with food.
This medication should take effect within 1 to 2 hours; however, effects may not be noted outwardly, and laboratory tests may need to be done to evaluate this medication’s effectiveness.
What if I miss giving my pet the medication?
If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.
Are there any potential side effects?
Methazolamide may cause the following side effects:
- vomiting, diarrhea, or lack of appetite
- sleepiness
- disorientation
- excitement
Serious adverse reactions may occur. If any of the following signs develop, stop giving methazolamide and contact your veterinarian immediately:
- heavy panting
- abnormal bleeding, bruising, or infections (signs of decreased blood cell counts)
- increased drinking and urination (signs of kidney problems or blood sugar imbalances)
- yellowing of the skin, eyes, or gums (signs of liver problems)
- muscle weakness or abnormal heart rhythms (due to low electrolytes)
- muscle tremors or seizures
- skin rash
- persistent vomiting
- bloody diarrhea
- persistent lack of appetite
This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.
Are there any risk factors for this medication?
Methazolamide should NOT BE USED in pets that:
- are allergic to it
- have significant liver, kidney, or adrenal disease
- have electrolyte imbalances
- have severe obstructive lung disease
- have closed angle glaucoma
Methazolamide should be USED WITH CAUTION in pets that are:
- pregnant or lactating
- using topical eye drugs for glaucoma
Are there any drug interactions I should be aware of?
The following medications should be used with caution when given with methazolamide:
- aspirin
- digoxin
- insulin
- methenamine compounds
- phenobarbital
- potassium and drugs affecting potassium
- primidone
- quinidine
- tricyclic antidepressants
Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.
Is any monitoring needed with this medication?
- Your veterinarian will monitor eye pressure regularly to be sure that the medication is working.
- Your veterinarian may monitor electrolyte levels and blood cell counts.
- Monitor your pet at home for serious side effects.
How do I store methazolamide?
- Store the tablets at room temperature in a tight container.
- Protect from light.
- For compounded medications, follow the storage directions on the label.
What should I do in case of emergency?
If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.
