Methimazole Gel Pen for Cats – Pros and Cons

Feline hyperthyroidism

The Methimazole Gel Pen can be used to treat feline hyperthyroidism.The medication is called: Methimazole: Twist-a-Dose Transdermal Gel. I guess you regulate the amount deposited (applied) by twisting the pen. The device that delivers the dose is somewhat like a felt-tip pen and it is delivered onto the hyperthyroid cat’s ear.

Hyperthyroidism raises the metabolism, makes the cat very hungry with weight loss. There are other symptoms.

The medication is methimazole (trade name: Tapazole or Felimazole) and it blocks production (synthesis) of the thyroid hormones, triiodothyronine (T3) and thyroxine (T4). The medication is absorbed into the bloodstream through the thin skin of the ear flap where there is little hair.

The upside is convenience and a reduced exposure to the medication by the pet owner. The downsides are some possible serious side effects, which should be carefully checked and explained by the vet and the possibility of a cat or dog in a multi-companion animal household licking the chemical off the cat’s ear and ingesting it. If a young kitten licks off the chemical I can imagine possible serious consequences.

As a result, steps would have to be taken in a multi-cat household to prevent that happening. What to suggest? The difficulty is knowing how long it takes to absorb into the bloodstream. I think the vet should be asked that question. If it takes 1 hour the cat’s owner can isolate the cat receiving the treatment for one hour. That is the simple solution I would have thought.

Also there are question marks about how well the medicine is absorbed into the bloodstream. Apparently a study indicated:

Only two of six cats tested had any detectable methimazole in their bloodstream¹

Methimazole is also used in treating hyperthyroidism in people. There are other versions of this drug. One is in the form a pill and it is sold as Felimazole®. One side effect of Felimazole is vomiting. This drug certainly requires careful administration and accurate dosage management. But this is a serious and common feline disease.

“Feline hyperthyroidism is one of the most common chronic diseases we see in the middle-aged and older cat”.²


  1. Ref:
  2. Your Cat ISBN9 780312 358013 quoting
  3. Photo of cat suffering from hyperthyroidism at a veterinary clinic. Published with permission but copyright the Nottingham Vet School.


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Methimazole Gel Pen for Cats – Pros and Cons — 15 Comments

  1. My cat is on this gel. She cannot get to it once it’s in her ear and the amount given is tiny. I do have to make sure it’s down inside the ear fairly far, but cats cannot lick inside their ears so as long as it’s in the ear they won’t ingest it. It’s much easier to give her this gel than to try and get a pill down her throat. She actually jumps on the bed now so I can clean the opposite ear and dose the other one. Less traumatic for everyone involved.

    • Thanks for sharing your experiences with this product – it is appreciated and it is useful information.

  2. Well, talk about cherry picking your data with the statement that only two of six cats showed detectable levels of methimazole. You really need to state up front that this was a single dose study in healthy cats. Further, in the paragraph just above the one where you cherry picked your viewpoint, is a description of a study where 9 of 10 hyperthyroid cats showed clinical improvement on transdermal methimazole.
    The fact is, this is a very safe method of treatment. Not all cats do respond, but in my practice, it appears that about 75% do respond positively.

      • I have been using methimazole transdermal twist a dose gel for my hyperthyroid cat for over 3 years and it’s been great! I just wish I had found out about it sooner b/c I lost a cat due to a stroke induced by hyperthyroidism.

        • Same here, pills didn’t work,she is now a totally different kitty, just wish I could buy it on line as through the vets it cost s me over £1000 a year but wouldn’t trade her for the world, she is nearly 16 and is like a kitten.

  3. This seems far from accurate dosing and too easily shared amongst other cats in the household as well as anything else the cat comes up against. If all this is for convenience for the owners then for goodness sake man up people and give you cat the treatment in the traditional way!

  4. Far too risky for me. Any cat, even the dosed cat, has access to be able to ingest the gel.
    Plus, I’m not too surprise that a study would show none or minimal amounts in the cats’ bloodstreams. I don’t think the ear flap of cats are vascular enough for the gel to be absorbed into the system.

  5. Well this is new to me and I can’t say as I like the sound of it very much. What about the cat himself washing the ear this medication is put on and swallowing some?
    This is why spot on flea treatment is put where the cat can never reach to get any on his paws or tongue.
    Is this gel just another easy way out to medicate a cat?
    Very worrying!

    • My cat has been on methimazole gel for two years, no problems at all with washing,my only problem is the manufacturer runs out for some reason then my blood boils as I have worked long and hard to get her where she is today,back to her weight level, glossy coat,so not amused, don’t seem to be able to buy it on the internet and very very expensive from vets.

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