Transdermal Methimazole Treatment For Hyperthyroid Cats


Katie, hyperthyroid. Bless her.
Katie, hyperthyroid. Bless her. Photo Alan Turkus
I’ll get straight to the point. Transdermal Methimazole treatment works but ask your vet. That is the general conclusion. I had to check. There has been a useful clinical study on this. They concluded:

“Clinical improvement, as well as a significant decrease in T4, was noted in all cats.”

T4 means serum thyroxine levels. In layman’s language the treatment reduced the amount of thyroid hormone in the cat, which is the objective because hyperthyroidism is an excess of the hormone due to over-production.

This video show how to apply the drug and clean the cat’s ears because the gel builds up. Ear cleaning should be done carefully and this presenter is careful and thoughtful. The interesting aspect of this is that the drug is absorbed through the skin and where the skin is thin allowing absorption into the bloodstream is the ear flap (the bit of the ear that you see). Applying drugs this way is called “transdermal” meaning via the skin.

There are of course some negatives to this one of which is that the ears need cleaning.  The video also covers this. The gentleman presenter has a very gentle and sensible approach which is ideal.


Hyperthyroidism is most common in middle-aged and older cats caused by these environmental factors. The prevalence is 0.33%. This means a third of one percent of all cats get it; quite a high figure when you work out the numbers – about 3 million domestic cats in the USA.

Transdermal application avoids “oral daily administration” which I presume means giving pills to a cat – hurrah! Incidentally the treatments listed on the top website (Google search) for this feline condition does not refer to transdermal methimazole. They list treatment with radioactive iodine and surgical removal of the affected thyroid gland as alternatives to oral medication.

Another benefit of this method that it requires a lower dose can be used:

“a lower dose of methimazole can be used to obtain an equivalent plasma concentration and clinical effect, with reduced risk of side-effects”

A concern is whether this treatment damages the delicate skin of the ear. Apparently the study found that it did not except for one of 13 cats. To quote:

“no cutaneous reactions were noted at the site of the application of the methimazole gel during the length of the study”

The assessment is qualified by saying that they can’t be sure there won’t be some problems in the long term. Always ask your vet about treatments such as this as they should be up to date.

12 thoughts on “Transdermal Methimazole Treatment For Hyperthyroid Cats”

  1. Michael,his skin is perfect and there are no lesions or red swellings as in dogs having scabies.His fur is growing back in places where i have removed the matted fur.He is absolutely normal, hale and hearty. Just wondering as to the type of this unusual disease of skin shedding akin to a snake.He is 5 years old.
    Below is a photo of “Matata” after the bathe and removal of “Dead Skin” from his hind thighs.

  2. This is quite uncommon amongst cats, as you know. Taurine in the diet is important. This is quite common, though, with veterinarians checking for hyperthyroidism. It’s basic, as far as testing. But the occurence is rare. You are right, Michael. It still needs to be addressed. It is quite possibly a solution with some cats. Every symptom should be addressed. There are more important issues that should be addressed first. Focus on those.

  3. as it is akin to trying to tame a miniature leopard!

    That made me laugh. You are not alone. There is a new service in the UK called Talk To The Vet. You can get one to one Skype consultation for a fixed fee. That would probably suit you! But I am not sure it will work.

    Rudolph I can’t figure out the orientation in the photo. Are you saying he sheds lots of fur? Is his skin OK? Are red bumps etc.? Does he scratch his skin? Remind me how old he is, Rudolph, please. If you can get a fresh picture I’ll try and give you some ideas. You might try the talk to the vet link above. You’ll get a British vet! The best … 🙂

  4. I can’t take my 5 year old male tomcat “Matata” to the vet as it is akin to trying to tame a miniature leopard!He is absolutely nervous of strangers and would scratch or bite if forcibly put into a enclosed “Cat Box”.Since his birth he has never ever been taken to a vet and luckily till date he is normal,. He has been suffering from some strange “Skin Disease” caused by flea infection and i have been bathing him with anti-flea shampoo.His entire fur sheds akin to a dead animal being skinned.I can’t take him to a vet to understand the reasons for his skin peeling off and the vet doesn’t attend pet patients at home.I totally agree with Mark that Veterinarian doctors should try to make home visits if possible.I have posted a photo of “Matata’s” shedding fur.Notice the parting of the fur mat near his hind leg. I gave him a bathe yesterday and cut off the hanging fur mat which resembles a small carpet !Thanks to “P.O.C” at least we can learn from our own cats and discuss their ailments.

  5. Not sure I could easily give my cats any kind of medication. They are not used to being handled and pushed so it would be quite difficult no doubt. I think it might even be almost impossible depending on what I’m trying to do. I would not be able to force them to swallow pills or accept an ear cleaning.

    Since we are on the subject of medicating cats – it’s important that cats be treated totally differently to dogs in these scenarios. Actually – I think that for regular checkups, boosters, even taking blood for tests or other basic procedures – vets should go to the homes. Infact I think they must. Cats shouldn’t travel. In Canada we had a great Indian vet who would come to the house for many things. It was such a relief. And he charged low prices. I’m sure you can guess that he basically had a full timetable of customers. Everybody wanted him. He could take all the business he wanted with a service like that.

    Cats need vets like him. Cats get sick when they are stressed. Taking a sick cat regularly to the vet is an awful thing to have to do to a sick cat. There’s a hugely unfair balance of money, research and activity in the vet industry – and cats are on the loosing end. Dogs have always taken first place. There should be more cat only clinics too.

    Putting cream on their ears would take me quite some time. It might take me a month or so to be able to do it properly.

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