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Product Info
How to Use
Customer Reviews
Product Info
What is Methimazole?

Methimazole is used to treat hyperthyroidism in cats. It has largely replaced propylthiouracil in this treatment process since it has a lower incidence of adverse side effects. Methimazole requires a prescription from your veterinarian, and is sold per tablet.



  • Effectively treats hyperthyroidism in cats
  • Rapid results
  • Affordably sold per tablet
How it Works:

Hyperthyroidism is a condition that occurs when the thyroid gland produces too much thyroid hormone. Methimazole inhibits the production of thyroid hormones.


Blood tests must be done to check for proper dosage. Do not use in pregnant or nursing animals. Do not give your pet a live vaccine while giving methimazole. Contact your veterinarian immediately if your pet develops signs of an infection.

Brand Name:

Tapazole (Jones)

Generic Name:


What is Methimazole:

Methimazole prevents the thyroid gland from producing too much thyroid hormone. Methimazole is used to treat overactive thyroid (hyperthyroidism). It is also used before thyroid surgery or radioactive iodine treatment. Methimazole may also be used for purposes other than those listed in this guide.

What should I discuss with my veterinarian before giving Methimazole to my pet:

Tell your veterinarian if your pet has an allergy to methimazole or if your pet has liver disease, a blood cell disorder, or a weak immune system. Tell your veterinarian if the pet is pregnant or nursing. Inform your veterinarian of any other medications, including vitamins and supplements your pet may be taking while receiving methimazole.

What is the most important information I should know about Methimazole:

Methimazole is a prescription medication not FDA approved for veterinary use; however, it is a commonly accepted practice for veterinarians to use this medication in cats. Methimazole is available as a 5mg scored tablet. The usual initial dose for cats is 5mg every 8 to 12 hours. Do not give methimazole to pregnant or nursing animals. Methimazole can increase the risk of bleeding. Methimazole can lower the blood cells that help fight infections. Your veterinarian will need to give blood tests on a regular basis to be sure these blood cells do not get too low. Do not give the pet a "live" vaccine while the pet is taking methimazole. Methimazole is needed for the life of the pet. If the medication is stopped, the symptoms will reappear.

How should this medication be given:

Give this medication exactly as directed by your veterinarian. Do not give in larger amounts, or give it for longer than recommended by your veterinarian. Follow the directions on the prescription label. If you do not understand the directions ask the pharmacist or veterinarian to explain them to you. Methimazole can be given with or without food. Allow plenty of water for the pet to drink. Store methimazole at room temperature away from moisture and heat. Keep this medication away from children and pets.

What happens if I miss giving a dose:

Give the missed dose as soon as you remember during the same day. However, if you don't remember until the next day, skip the dose you missed and give only the next regularly scheduled dose. Do not give a double dose of the medication.

What should I avoid while giving Methimazole to my pet:

Do not give the pet a "live" vaccine while the pet is taking methimazole. Contact your veterinarian at once if your pet develops signs of an infection.

What are the possible side effects of Methimazole:

If any of the following serious side effects occur, stop giving methimazole and seek emergency veterinary medical attention; an allergic reaction (difficulty breathing; swelling of the lips; tongue or face; hives). Stop giving methimazole and contact your veterinarian at once if your pet develops any of these serious side effects; fever, chills, body aches; easy bruising or bleeding, unusual weakness; blood in the urine or stools; severe blistering, peeling, and skin rash; nausea, low fever, loss of appetite, dark urine, jaundice. Other less serious side effects may occur. Continue giving methimazole and talk to your veterinarian if your pet experiences headache, drowsiness, dizziness; mild nausea, or vomiting; itching; muscle, joint, or nerve pain; swelling; hair loss. Other side effects may also occur. Talk to your veterinarian about any side effect that seems unusual or bothersome to the animal.

What other drugs will affect Methimazole:

Tell your veterinarian if your pet is taking theophylline (Theo-Dur), warfarin (Coumadin), digoxin (Lanoxin), a beta blocker such as atenolol (Tenormin), metoprolol (Lopressor), or propranolol (Inderal). Drugs other than those listed may also interact with Methimazole. Talk to your veterinarian or pharmacist before giving any prescription or over the counter medicines.

How to Use
  • Methimazole is a prescription medication used by veterinarians to treat overactive (hyper) thyroid in cats.
  • Methimazole is not FDA approved for use in veterinary medicine; however, it is a commonly accepted practice for veterinarians to prescribe this medication for cats.
  • Methimazole is also used before thyroid surgery or radioactive iodine treatment.
  • Periodic blood tests will be necessary while the cat is taking this medication.

Do not use in pregnant or nursing animals. Methimazole can be given with or without food.

All weights
The usual initial dose varies from 2.5-5mg 2 or 3 times a day. Periodic blood testing is required to monitor liver function and for any toxic effects on blood cells
Do not use!
Do not use!

Store methimazole at room temperature, away from moisture and heat.

Active Ingredients (per tablet)
5 mg
Other Ingredients: Lactose Monohydrate, Povidone, Talc, Croscarmellose Sodium, Magnesium Stearate, Corn Starch.
Customer Reviews
Methimazole is rated 4.628318584070796 out of 5 by 113.
Rated 5 out of 5 by from Happy Kitty Again My 16 year old cat is hyperthyroid and had lost a few pounds despite her voracious appetite. She stopped purring and was lethargic and ill. The doctor put her on 5 mg twice a day, and in just one month she has gained a whole pound and her blood test numbers are much better! She is acting more like her old self too. I crush the pill and mix it with Fancy Feast and she doesn't even seem to notice it. Love this stuff!
Date published: 2016-06-22
Rated 5 out of 5 by from Works well I was originally getting the "mini-melt" variety from my vet, but a friend told me about 1800petmeds. Even though this isn't the mini-melts, they still work well. I soften it in a little bit of warm, lactose-free milk then crush it and mix it up and Oreo thinks it's his special treat. The only downside is that they come in 5mg pills, which mean I have to cut one in half for his evening dose. But it's working well and he's gaining weight and looking healthy again.
Date published: 2016-05-01
Rated 5 out of 5 by from Worked Fast Kitty started losing weight and was diagnosed with hyperthyroid. The pill treatment was the best option for us and it has worked really well. She started gaining weight within a week. The delivery was very quick, I had the medication within 3 days with very little effort on my part. This is also a lot cheaper then buying though the vet office.
Date published: 2016-02-03
Rated 5 out of 5 by from Effective, but lifetime solution? My beloved kitty of 15 years was just diagnosed with hyperthyroidism. I was devastated to learn I had to give her a pill twice a day most likely for the rest of her life... 5 years? Adding the cost of that and the trauma for her and I, I looked into other options. Surgery - with easy post op period. Radioactive treatment - a one time dose then 7 days in hospital isolation. Has anyone done this? For now this medication is working. 5 mg in the am and 2.5 mg in the pm -pill popped into her mouth which half the time I find laying around later on. She's been on it for a month and her level has come down to 7 from 11 with the goal level at 2.0 I'm going to try the pill pocket or the cat sip stuff while waiting for the cat pharmacy locally to compound this into a liquid which would be much easier . We travel allot though and my cat sitter has already let me know she won't be caring for our Bebe if she has to give meds.
Date published: 2016-01-15
Rated 5 out of 5 by from I tried to avoid it, but.... Nikita's veterinarian is holistic so of course we first tried homeopathic remedies, but they didn't work for Nik's hyperthyroid. As a last resort we put him on Methimazole. He has vastly improved, stopped his screaming, is happy and looks great. They're also easy to administer. The crew at 1-800petmeds is also wonderful and very caring. Thank you.
Date published: 2015-12-18
Rated 5 out of 5 by from Easy to give,m cat loves it Sandie takes half a pill in her favorite tuna am and pm
Date published: 2015-11-29
Rated 5 out of 5 by from Fast and Effective results Kringle has been on Methimazole for 6 mo. When diagnosed she only weighed 6 lbs and her fur was thinning terribly. She could not keep any food down, our Vet said she was failing fast. On this medication, within a couple weeks she started putting on weight and her fur was already starting to thicken. Now she looks and acts like another cat. You would never know she has a health problem. She is 13 years old, and acts like a kitten, full of energy, Appetite is normal, and no more throwing up food. I dissolve the 1/2 pill she is prescribed twice daily in a table spoon of Cat Sip, and she laps it up. She actually cries for her medication now, she wants it, which is fantastic.
Date published: 2015-08-10
Rated 5 out of 5 by from EXCELLENT RESULTS My sweet little "kitty" turned 19 last week. She's been diagnosed with hyperthyroidism for 6 years, so has been using Methimazole for those 6 years. Yesterday we took her to the vet for her annual blood work and check up. All the vet could say, was "WOW" as her blood work couldn't have come out better. She's on two pills a day which we give with her food in the am. And with the kidney food, she even came out pretty good on that. I'm hoping to see her into her 20's.
Date published: 2015-07-25
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Felimazole and Methimazole

Hello, My cat has been on Felimazole. Can I get Methimazole with the prescription for Felimazole that my vet has written?
Asked by: H
Felimazole tablets are coated. Methimazole is just a regular tablet, with no coating on it. The methimazole from us would require a new prescription from your vet written out for methimazole.
Answered by: Kelly P
Date published: 2015-07-03


Asked by: TIGERGAL
HI Nancy. We do not have a pen. We have methimazole transdermal gel syringes in 100mg/ml 1 ml size and also 50mg/ml 1 ml size. Please call our customer care department and tell us the dose in mg's you give your kitty a day. We will be happy to help you figure out the price per month. Thank you !
Answered by: Linda M 1800petmeds pharmacist
Date published: 2015-04-29

Can you recomend a very good supplement that I can give my high thyroid kitty? been on Methizamole about 2 years.

Asked by: Gan
Speak with your veterinarian before starting your pet on any supplements to determine if your cat could benefit from its use and which one would be most appropriate. 1800Petmeds does carry an Endocrine Package however it is recommended for dogs. It is an ideal set of supplemental products for any dog with an endocrine-related illness (Diabetes, Hypothyroidism, Hyperthyroidism, Addison's Disease, and Cushing's Disease). The products included are Proanthozone which helps maintain your pet's health against cell damage, especially in the liver and kidneys that may be caused by long term medication use; NaturVet Enzymes and Probiotics which helps to maintain digestive health and strengthen your pet's immune system; and Super Pure Omega 3 which restores your dog's coat and skin health.
Answered by: Cheryl-Pharmacist
Date published: 2015-04-28

Can I get the Methimazole in a gel instead of a tablet for my cat?

We have 3 elderly cats and I want to make sure she gets it instead of the other two. The ear application seems like a good way. It is working so far but is a bit pricey. I was curious to see if you offered it and what the cost is. Thanks!
Asked by: Smokey
Yes, we do carry the transdermal methimazole !! Please call our customer service department for prices.
Answered by: Linda M 1800petmeds pharmacist
Date published: 2014-11-27


is this the same type of Methimazole that I take (as a person) for hyperthyroidism?
Asked by: Lu
Methimazole tablets are used in both humans and cats in the treatment of hyperthyroidism.
Answered by: Cheryl-Pharmacist
Date published: 2014-11-08


does it come in 6mg liquid?
Asked by: jan
The concentration of the liquid methimazole we carry is 5mg/mL. This can be purchased in 15, 30, 60, 90, and 120 mL bottles.
Answered by: Cheryl-Pharmacist
Date published: 2014-11-03

Can Methimazole cause red bumps on my cat's neck?

My cat Snowy was put on 2.5 mg of Methimazole twice a day. His blood was tested after one month and his T4 levels were back to normal. He became more active with a better appetite and didn't act at all like the 19 year old that he is. Now almost 2 months on the medication he is getting red raised spots in several places on the back of his neck. Some have scabs so I think he must be scratching them. Could this be a reaction to the Methimazole and if so why would it take so long to show itself?
Asked by: Snowy'sDad
Considering that your pet only started having this problem now and he's been on the medication for awhile it may not be a result of the medication. However, contact your veterinarian as they may want to examine your pet to determine the cause and if treatment is necessary.
Answered by: Cheryl-Pharmacist
Date published: 2014-09-27

Can Methimazole make my cats utine have a very strong odor?

Sine my can started taking methimazole his litter bis has an extremely pungent odor. The whole house stinks. Could this be a side effect?
Asked by: Karadono
I would mention this to your veterinarian
Answered by: Linda M 1800petmeds pharmacist
Date published: 2014-09-03
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