Reducing Methimazole due to side effects

[tayallen22]

My cat recently was diagnosed with hyperthyroidism so I've been trying to do some research. She's 9 and we recently started the transdermal Methimazole gel - started it about 2 1/2 weeks ago. She was put on the 5mg dose (2 rotations of the pen) once per day. I noticed after being on the medication for about 2 weeks, she was overgrooming and itching around her ears and face quite a bit. She was also constantly vomiting (with and without hairballs). I called my vet to inform them of what had been going on and they had me bring her in so they could take a look at her. The vet said that her symptoms could be side effects from the medicine and recommended we stop the meds for about a week and see how she's doing. If doing well at that point, then we could restart the meds, but at half the previous dose. I'm curious to know if anyone has tried decreasing the dose of the Methimazole gel and if that seemed to help lessen the side effects it can have while also managing their cat's thyroid levels?

Also Laura304 , I'm curious as to how your kitty is doing after it being a while that she received the radioactive iodine treatment. I'm wondering if it's worth the cost to get the treatment now rather than having to keep trying my cat on and off meds with her feeling miserable while doing it.

Would love for anyone to share their experience with their hyperthyroid kitties!

Thanks in advance!

 

[FeebysOwner]

My cat recently was diagnosed with hyperthyroidism so I've been trying to do some research... I'm curious to know if anyone has tried decreasing the dose of the Methimazole gel and if that seemed to help lessen the side effects it can have while also managing their cat's thyroid levels?

Hi. It would seem, based on what I have read on this site as well as some other forums - and from my own experience - that vets always go overboard with the dosage to begin with, and what your vet is recommending to remedy the situation is accurate.

Most cats do much better when started off on a lower dosage, and adjust it as needed after follow-up blood work, which should be done at 3 weeks following the onset of meds, and again after 4 more weeks have passed, especially if a dosage adjustment was needed at the 3 week mark. It is also more advisable to split the dose and administer it every 12 hours, so that the meds are more balanced in the system at all times.

My vet wanted to administer 5mg twice a day (we use pills, not the transdermal form)!! After I researched the matter and talked to him, we agreed to start Feeby on 1.25mg twice a day. That was back in October 2020, and Feeby's T4 was 4.5. After follow-up blood work was done, this dosage was working well and Feeby was not having any kind of side effects. She had an increase to 1.875mg AM/1.25mg PM in March 2021, and we just increased her dosage to 1.875mg twice a day about 3 weeks ago, because her T4 is inching up again. One of the vets I recently saw thought the dose should be increased to 2.5mg twice a day, and I said no way. I will have her retested and if need be, I will elevate the dosage again, but probably not even then to the level this last vet suggested.

Please be aware that sometimes when the hyperthyroidism is brought under control, it can unmask kidney issues, so keep an eye on her blood work numbers related to her kidneys as well.

Regarding Laura304 - she has not been on this site since early 2019, so it is not likely you will receive a response from her. Normally, a cat's thyroid level needs to be stabilized through the meds first before pursuing radio iodine treatment, so you will need to go through that process anyway. But, there are others who have gone through the treatment that can answer your questions once they see your post. I chose not to go that route with Feeby given her age (17+yo).

Here is a site that you might be interested in regarding hyperthyroidism and radio iodine treatment - Animal Endocrine Clinic | Where science and compassion cure.