One of my cats was diagnosed with hyperthyroid 5 weeks ago, as she was like a little skeleton with fur and couldn't eat enough food. She was very thin, ravenously hungry, but had no other symptoms apart from a T4 reading of 116. All other blood tests were normal.

My usual senior vet put her on 2 x 2.5mg Felimazole a day for a month which I gave her one tablet 12hrs apart. She then commenced the second month of Felimazole at 2 x 2.5mg a day. After a few days she started to deteriorate, she was like a dead thing, laying around and not wanting to eat or do anything. I rang the vet and she had more blood tests. Her T4 level was now down to 9.1 which the young girl vet said was dangerously low which was as bad as being too high. The young girl vet told me to reduce the dose and give 1 x 2.5mg a day. I have a feeling she had been overdosed with 2 tablets a day for the second month.

She wasn't better after a day or two and was still vomitting, so I rang the vet again and took her in for an examination and more blood tests. These came back more normal, and another senior vet said there was no major organ damage and that these blood results were the best she'd had. He told me to stop the tablets over the w/end then if she was ok, give her 1 tablet a day.

(There's 2 senior vets at my surgery and a couple of young ones just out of vet college).

She's been vomitting ever since going on Felimazole, she had been sick occasionally but not as frequently as she had been while on Felimazole.

She was so sick over the w/end I didn't give her the tablet and she wasn't sick all day, but the following day once she'd had the tablet she was back to vomitting again. She's not hungry at all and hardly eats now.

She's almost 16 but she doesn't look it and the vet was surprised she was that age, as she has clear eyes, good teeth and a wonderful coat, and she looks more like a 5yr old. Her mother who is about 6mths older is also young and fit for her age too.

Would Vidalta cause nausea and vomitting like Felimazole does? If so, would it be ok to stop the treatment until her quality of life was noticably deteriorating and then have her put to sleep? She was much happier before she started the Felimazole apart from the hunger and restlessness.

And as vomitting and nausea are side effects of Felimazole, how long is it before the side effects stop altogether? Or don't they?

My cat was being sick before being tested for hyperthyroidism, and had been for some time, but the vet didn't make much of that and gave me the impression it was part of the condition.

So I'm unsure whether the vomitting is from before the Felimazole or the Felimazole is aggravating it.

I always give my cat her tablet about half an hour to an hour after her b/fast, hidden inside a small piece of chicken, as she gobbles it down without much chewing. I did try hiding it in a small ball of cheese but the cheese made her sick straight away.

She's gone 2 days now without a tablet and hasn't been sick and seems much better in herself, but I don't want to go more than 3 days without a tablet really, so am waiting to hear from the Vet here before deciding what to do next.

I'd rather she had a happy shorter life with no treatment than an unhappy longer life from being treated and vomitting every day. Although it was heartbreaking before the treatment when she was so thin, even tho she was happy in herself.

Thanks

PS: 3 days with no tablet now and she's not been sick since, but her hunger is getting back to what it was before the tablets.

Hi There,

I'm sorry to hear your cat is struggling with her hyperthyroid treatment. In answer to your question, one of the side-effects of both Vidalta and Felimazole is vomiting, however it tends to be temporary and resolve over time as things start to settle down. I can't tell you how long though as it differs according to individuals.

Unfortunately I also can't advise you on the best course of action to take as I haven't seen your cat myself to do a clinical exam or seen her clinical records, as such your current vet is definitely the best person to speak with and request advice from. I can tell you that the vomiting prior to treatment would most likely have been linked to the overactive thyroid though as GI signs are a common presenting symptom with this problem. However, there may also be another reason for the vomiting and without further diagnostic tests to rule out other causes, your vet would be making the most logical conclusion.

If you do discontinue treatment your cat will revert back to full-blown hyperthyroidism and all the symptoms that it entails. She will probably regain her appetite, but continue to lose weight, the vomiting is unlikely to stop (if it's linked to her thyroid problem) and she may develop and increased thirst and frequency of urination. Additionally she may also develop diarrhoea and it could affect her cardiovascular system too, which may lead to heart failure. I'm sorry to be the bearer of bad news, but if you discontinue treatment you should be aware of the risks. The treatment does have it's own side-effects as you've discovered and it takes some time to get the dosage right for each cat, which is why repeated blood tests are required to tailor the dose and also keep an eye on her kidney function.

Finally, there are also alternative treatments to oral medication and they are surgery to remove the affected thyroid gland or radioiodine therapy. Please do also discuss these options with your vet.

I hope that helps a little & best of luck!

Zara The Vet

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