Cat experiencing hyperthyroid medication side effects

duffo

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Hi,

My cat (age 8-10ish) was recently diagnosed with hyperthyroidism after losing 3lbs in one year (not really other symptoms). I was told a normal T4 range is 10-60, and hers was 184. I started her on felimazole (2.5mg twice daily), and am now at the 3-week mark. The follow-up blood test shows her T4 is now 38, so back to normal as long as I keep the dosage up. However I am dealing with side effects!

First of all, the vomiting - started about 5 days ago she has puked 1-3 times every day. It happens at random times and isn't associated with feeding or pilling times, although seems more common in the early morning. She'll do the classic cat pre-puke yowl, heave and puke out some yellow-ish liquid and the occasional hairball if she has one.

Second of all, she has always had some allergic sensitivities which I have never been able to narrow down to a specific source, but she started itching her head a bit raw, between her eyes and ears. She has a history of this pre-HT and its possible its the current dry food I started feeding her not too long ago, which has chicken & rice, so I am going to switch over to grain-free, as well as swapping out the 'seafood supper' fancy feast for a slightly higher quality variety and upping the wet:dry food ratio to get more moisture in her. I had to cone her to get it to heal which always makes her very lethargic, so she's in a bit of a funk right now.

Has anyone dealt with this before (I am assuming yes)? Specifically the vomiting, does it go away after awhile? It only started after 2 weeks and is now a more-than-daily occurrence. I'm aware of the radiation treatment, but it is not super available in my area and sure to be extremely expensive. I will look into it more but I am ok with medicating long-term as long as the side-effects clear up.
 
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duffo

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Hi
Is your vet adjusting the dosage? Are they aware of the vomiting?
The vet is aware and I spoke with them today. Since she has just stabilized her thyroid levels, the plan for now is to maintain the dosage and re-assess once her next test result comes back in 3 months. If the vomiting continues consistently for the next week or two I'll give them another call.
 

LTS3

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Chicken is a common cause of food allergies / sensitives so if you can feed your cat something else, that would likely help. Try a novel protein like rabbit or venison. There are brands with novel proteins in both canned and dry. Give a new food at least 13 weeks or so to see if it helps the itchy skin or not. Gums and other fillers in food can also cause food allergies. In some cats, it may be some form of fish, even fish oil. It'll take awhile to eliminate ingredients one by one to see what helps your cat's itchy skin. There is allergy testing the vet can do but it's not always accurate.

How is your cat at taking the pills? If it's difficult, you can try Pill Pockets or one of suggestions here. You can also have the Felimazole (methimazole) compounded. Some people find that the transdermal gel is the easiest way to dose the cat.

Ask your vet about an anti-nausea to help with the vomiting.

Take a read through the Felimazole prescribing info: Felimazole - FDA prescribing information, side effects and uses There are some common side effects and more concerning adverse reactions.
 
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duffo

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Chicken is a common cause of food allergies / sensitives so if you can feed your cat something else, that would likely help. Try a novel protein like rabbit or venison. There are brands with novel proteins in both canned and dry. Give a new food at least 13 weeks or so to see if it helps the itchy skin or not. Gums and other fillers in food can also cause food allergies. In some cats, it may be some form of fish, even fish oil. It'll take awhile to eliminate ingredients one by one to see what helps your cat's itchy skin. There is allergy testing the vet can do but it's not always accurate.

How is your cat at taking the pills? If it's difficult, you can try Pill Pockets or one of suggestions here. You can also have the Felimazole (methimazole) compounded. Some people find that the transdermal gel is the easiest way to dose the cat.

Ask your vet about an anti-nausea to help with the vomiting.
The food allergy thing has been a 2-year journey already, so far what I've found is that corn is bad, changing proteins doesn't seem to have a major impact (she was eating chicken in her food for the past few months without major issue - minor stuff like gunky ears seems to happen on every food), and that some of it is probably just seasonal.

Getting her to take the pills is no problem. I wrap it in a treat or cheese and she scarfs it down.
 

FeebysOwner

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Side effects of felimazole (or, any thyroid med) are most common in the first 2-3 months, so they could go away in time. But, since she has some 'room' to spare on her T-4 reading, I would ask the vet if you could lower her dosage by just a bit and see if that changes anything with regard to the vomiting.

Most times, it is wise to start at a more moderate dose, to let a cat's body get used to it, and then increase as needed after multiple rounds of testing. 2.5mg twice a day isn't horrific, but it would be considered on the 'higher side' as a starting dose. While I can see why the vet recommended it based on your cat's initial reading, I still think vets tend to want to drop the T-4 as fast as possible, even though that increases the chances of side effects. I hope your vet will consider this as an option. And, if they don't, I would not wait 3 months for a re-test.
 
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duffo

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As an update, the daily vomiting has stopped and she actually has not puked in 3 days. However she is still itching and creating some raw spots on her head. I am in the process of switching her food to grain-free.
 

Furballsmom

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Try some store-bought (not garden grown) chamomile tea. Brew it, cool it and apply to the itchy spots. It is anti fungal, anti bacterial, will ease the discomfort and is safe if she licks it :)
 
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duffo

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I should add, I did start feeding her some wet food with the pill as opposed to giving it to her outside of meal time, to help her digest it. Not sure if that was actually helpful to stop the vomiting or if it was coincidence, but just thought i'd leave that tip!
 

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If the vomiting starts to be a daily occurrence again and she seems to do well with the food transition , I would consider asking if you could switch to a transdermal formula for her meds. Sometimes their tummy can't handle it. 😀
 
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