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I am writing this article about felimazole as my stats show my site is getting searches for that as a key word. Felimazole tablets are given to control hyperthyroidism.
This is a common condition of older cats and is due to over-production of thyroid hormones from the cat’s thyroid glands. A pair of these glands is present in either side of the neck, but they are usually very small and difficult to feel. In hyperthyroidism, one or both glands become very much enlarged, often becoming easy to feel. Felimazole tablets contain the drug thiamazole which suppresses the amount of thyroid hormones released (called thyroxine, often known simply as T4, and triiodothyronine, known as T3). An enlarged gland will not shrink with treatment, but its activity will be controlled. There are 2.5mg tablets which are pink, and 5mg tablets which are orange, they are designed to be given directly into the mouth and swallowed whole. However this is very difficult with some cats so a “pill popper” might be useful.
Like all medication side effects are possible, mild side effects are not unusual, though the vast majority of cats show none at all, and thrive on treatment. The most common side effects are vomiting, going off food and becoming listless. Occasionally more serious side effects are seen and these can be quite varied. Some cats seem to feel itchy about their face and neck, they then scratch themselves and develop open sores and scabs on the head and neck. Other effects seen more rarely might involve the bone marrow, resulting in anaemia or abnormalities of the white blood cells and immune system. The mild side effects usually settle down after a short while and do not require treatment to be stopped. If more serious side effects are suspected, treatment should be stopped and veterinary attention sought.
In the UK felimazole is a prescription drug and so can only be obtained via your veterinary surgeon, I am not going to write on dose rates as this should be worked out by your veterinary surgeon following blood tests to work out the severity of your cat’s disease. Cats on this medication should have blood tests from time to time both to help your vet work out the dose rates and to check for side effects.
NEW! - Here is a link to the professional data sheet for this drug, this is the reference which veterinary surgeons will reach for when prescribing this drug , you can read a lot more about dose rates, contraindications and side effects HERE
Also there is a lot of information in the comments section of this article which can be seen below so have a look there as well, my special thanks to Irene Stanbrough in this regard.
Scott Nimmo BVMS MRCVS
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I asked my vet to ring the manufacturers of Felimazole because I wanted to cut the tablets to give a half dose. They advised against cutting or crushing the tablet. We decided with advice from the vet to give my cat one Felimazole 2.5mg every other day, we then did a full blood test (to include platelet count) after two weeks. The thyroid has started going down and my cat does get a little spaced out for a couple of hours after having the tablet, but we need to get the thyroid down. As there seems to be only the small side effect of the spaced out, dozyness – we have increased the tablet to one a day. My cat has a high thyroid reading so you may not need to increase. Ask you vet to ring the manufacturer if your worried.
Hello everyone,
I have put a link to the professional data sheet for felimazole towards the end of the main article above. It does cover side effects etc. in some depth.
Here is the link : http://www.noahcompendium.co.uk/Dechra_Veterinary_Products/Felimazole_ACY-reg_ADs-_2_5_mg_Coated_Tablets_for_Cats/-40417.html
Regards,
Scott
Plumb’s Veterinary Drug Handbook now recommends starting with 1.25mg BID, at least in their online version.
Our 18 year old cat was diagnosed a month ago. Her (UK) vet wanted to start her on Felimazole at 2.5mg BID but on advice from a feline hyperthyroid support group I asked if we could start with 1.25mg BID. She checked with the manufacturers, who said it was OK to split the tablet as long as we took precautions against absorbing any ourselves.
On her 3-week retest, her T4 was 16.3 nmol/L. If she had been started on 2.5mg BID as her vet originally intended, I think she would have been seriously hypothyroid by then.
To Jenny
Good Luck listen to your cat and your intuition but read all the info available and make your own decisions that feel right for both of you. 18 in a good age wish our cat could have lived that long.
Princes MUM XX
ps we were the first to blog some years ago maybe you read about our disaster with Felimazole
My 18 year old cat ‘Hennie’ has been on various doses of felimazole for the last year, however it has become really difficult to get her to take them. The straight down the throat option is totally ruled out – to the point I’m scared she’ll give herself a heart attack! No matter what tasty treat it’s added to prior to meal time, she manages to ‘spit’ it out! Can the manufacturers not flavour them with yeast or something cats adore?
Hi Sheena
Out Cat was exactly the same and we had to wrap him in a blanket bag to stop him escaping but that incurred stress so much so that he drooled had palpitations and we to thought he would have a heart attack to our neighbour put the pill in soft flavoured garlic cheese for his cat and that worked but not on our Prince and also butter on the tip of his finger with the pill inside I think but cats intuition out smarts us humans so we were never lucky to get the pill down without the bag and holding his jaws/mouth open it was a nightmare so feel for you.
So Sorry no answer just wish we had not out our puss through all that and still convinced the pills made the condition worse but thats our families opinion not a medical one.
good luck and fingers crossed for you and your cat.
Irene Stanbrough
Thank you Irene. I must say though, thanks to this blog I am now using the DeFurrums as suggested and they work a treat!!
Thank you from a happy Cat and Mummy x
I had similar problems trying to get my female 17 yr old to take felimazole, she would vomit, she was still losing weight. In the end I found an alternative herbal Canadian medicine in drop dosage into her food and homeopathy tabs crushed in her water. She had her good days and bad days. I just know I could not have put her through the terror of tablets each day and her being upset with and vomiting. She became very week and was euthanized on Tuesday, I still don’t know if I did the right thing or not by changing her medication. But lets hope with the increase of hyperthyroidism in female cats friendly/stress free
medication will become available.