Hyperthyroid cat - Problems with Methimazole

carmenwiNovember 29, 2008

My cat was diagnosed as being hyperthyroid about a month ago. She was put on the pill form of Methimazole for 2 weeks & put on weight & seemed healthy for the most part, except she started itching her head a lot. She went in for a checkup & her bloodwork came back fine. So they prescribed the transdermal type of Methimazole. She seemed lethargic at first,now she's not eating at all (been a day & 1/2)& obviously isn't feeling good. I didn't give her the medicine last nite, this a.m. she's drinking water again & is back to being lovable. Still isn't eating but is definitely interested in food again, sniffing it a lot. Not sure what to do. Going to call the vet today & mention the symptoms. The medicine is definitely not agreeing w/ her. Just wondering if anybody else has had this happen & what they did about it.

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You may want to discuss the info below with your vet..........

Here is a link that might be useful: side effects

    Bookmark   November 29, 2008 at 11:58AM
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If your cat was tolerating the oral methimazole fine, why did your vet switch her to transdermal? What dose was she on with the oral, and what dose is she on now with the transdermal? What was her T4 blood level at diagnosis, and what was it at the two-week check? What type of thyroid test(s) was run? Total T4, Free T4?

We can give you more useful information if we have the answers to those questions. In the meantime, I strongly recommend joining the feline-hyperT
mailing list at Yahoo Groups. They can answer any and all questions you may have about this disease and its various treatment options.


    Bookmark   November 29, 2008 at 12:39PM
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I know that the itching is a common side effect of the Tapazole Thankfully, my Rex doesn't seem to suffer from it.

    Bookmark   November 30, 2008 at 10:54AM
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Ok, I dug thru the garbage & found her previous prescription for the pill form. They had her on 1/2 of a 5mg pill once/day. The thyroid test says it was Antech-T4. After the 2 wk trial period on the pill they called & said her T4 levels were perfect but they didn't give me any #s. I can always call & get them I'm sure. And will if you need them. I wasn't sure why they switched to the transdermal either (which the pkg says to use .05ML). I told them she was eating the pill fine if I crushed it into her soft food. I signed up for the Yahoo Feline HyperT group too. Thank you for that info. I appreciate any info I can get. She's started eating small amounts of food again but is picky....like she's not feeling good quite yet. usually not a very picky cat.

    Bookmark   November 30, 2008 at 7:14PM
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Some cats do not tolerate any form of methimazole- the itching and lack of appetite are both pretty common. If your cat's kidney values are good after a month of the methimazole, I would strongly recommend I-131 radioactive iodine to cure the hyperthyroidism. It is important to know the kidneys are in good shape before doing I-131 because being hyperthyroid is beneficial to the kidneys, and if you do I-131 then you cannot tweak methimazole to decrease symptoms of hyperthyroidism AND keep the kidneys healthy. If the kidneys are already healthy even after a month of methimazole, then doing I-131 isn't likely to harm the kidneys.

Some cats do not itch on the transdermal methimazole as much as the pill. I have seen cats with SERIOUS secondary infections and permanent scars because of the methimazole itching problem- that is why your vet switched to transdermal. But it is harder to regulate thetransdermal dose, and some cats get nauseous on methimazole in either form.

The only permanent cure for hyperthyroidism is I-131; methimazole simply suppresses the symptoms. Removing the thyroid glands helps some cats, but there are serious risks associated with the surgery and some cats continue to be hyperthyroid despite surgical removal of BOTH glands.

The forum Laurie mentioned is an excellent resource and I highly recommend it to all my hyperthyroid patients. Good luck with your kitty.

    Bookmark   November 30, 2008 at 8:08PM
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I have started my cat on Methimazole 1/2 tablet twice daily. Her personality has changed. She seems thinner. She shys away from me most of the time. She now started to have diarreha (sp). I feel she has totally change. I don't want to do the radioactive procedure...she is 14 years old and I feel if she is away from me in a cage for 2-3 weeks for the procedure she would just die. She is a siamese and she is very hi strung to begin with. I don't feel that this pill is doing the right thing for her. I will check up with my vet on Monday.

    Bookmark   July 10, 2011 at 10:26AM
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