# Methimazole dosage for HyperT



## ~*Regina*~ (Apr 16, 2008)

The vet is telling me to give Tessie 5mg tablets twice a day of the Methimazole for her HyperT, Isnt this high? I gave her the pill tonight but I am so nervous that its to much....


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## NebraskaCat (Jan 15, 2013)

I did a quick google and it pointed me back to this forum (of course), to this old thread...

http://www.catforum.com/forum/38-health-nutrition/119349-kitty-just-started-methimazole.html

And within that thread, someone provided a link to the Yahoo group for Feline Hyperthyroidism. Someone here (Stryker maybe?) frequently advises to go to those health issue-specific pages for help. The people who follow that advice usually seem pretty impressed with the information they receive there.


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## doodlebug (May 13, 2006)

No! No! No!....don't do it. My vet wanted me to start Maggie on 7.5mg twice a day. I didn't do it and gradually increased it. When we got to 3.75 twice a day she tipped over into hypothyroid after 3 weeks. Had I started her on the 15 mg a day it probably would have killed her. 

In addition, many cats are sensitive to methimazole and starting slow and building up helps them to tolerate it better. 

Generally recommended starting dose is 1.25mg twice a day, no more than 2.5 mg twice a day. 

Dr. Mark Peterson is one of the leading endocrinologists in the Hyper-T world:

Hypurrcat | Animal Endocrine Clinic

The Yahoo Hyper-T group is here:

feline-hyperT : A support list for people whose cats have been diagnosed as hyperthyroid (hypothyroid also welcome).

ETA:

And here are my threads on Maggie's Hyper-T saga

http://www.catforum.com/forum/38-he...ie-hyperthyroid-vet-moron-updated-1-19-a.html

http://www.catforum.com/forum/38-health-nutrition/152458-maggies-radioactive-iodine-treatment.html


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## ~*Regina*~ (Apr 16, 2008)

O no, i hope I didnt hurt her by giving the 5mg's tonight! I am so nervous now... I will be cutting those pills in 1/4 and calling the vet in the AM
If it's so dangerous why do they proscribe it!!

I just took a look at the Yahoo group, im pending approval with the admin.
Thanks!


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## doodlebug (May 13, 2006)

Because that's the manufacturer's recommended starting dose. My vet basically told me I was crazy, that he never had a cat go hypo by starting on that dose and I shouldn't believe everything I read on the internet....he's no longer my vet. I changed vets before Maggie went hypo, I probably should have gone back and shoved it in his face.


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## LCSP (Dec 31, 2012)

My cat is on 1.25mg twice a day and the blood test after one month showed his numbers are perfect. He'll continue at that level and recheck in a few months. We use a liver chew compounded with the meds, not pills, and my cat looks forward to them. 

Originally my cat's oncologist wanted him on 2.5mg twice a day. Our regular vet said 2.5mg once a day. I'm the one that asked about 1.25 twice a day. 

Definitely tell your vet you want to go slow to make sure not going overboard. It may mean more thyroid testing till you get the right dosage. Also, need to take meds twice a day. The meds have a 12 hour life in your kitty's system, so one pill a day does not work as well, throwing all systems off. What Doodlebug said was true about side effects. The slower you start, less chance of stomach upset or other side effects. My kitty has shown no problems with the meds.

I don't think taking one pill will negatively effect your cat, so don't loose sleep tonight. But do call the vet before continuing the meds tomorrow. Well wishes to your kitty!


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## ~*Regina*~ (Apr 16, 2008)

I just talked to the vet tech, she said the reason they gave her such a high dose was because her reading was 100? She said that is very high and they need to bring it down with the 5mg dosage 2 times a day. Usually they said they do say a lower dose but Tessie's case is different. I told her I do not feel comfortable giving her 5 mg 2 times a right off the bat and would rather do 1.25 mg or 2.5 pill 2 times a day instead.
The actual vet is going to call me when she gets in just to confirm and talk with me. The vet I go to is very nice and they work with you so I hope she is on my side when they call.


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## laurief (Jun 22, 2008)

Your vet's tech in misinformed. Here's how it works. Most hyperthyroidism is caused by a benign tumor in the thyroid glands that causes an overproduction of thyroid hormone. Since the thyroid is producing more hormone than the body needs, the excess hormone builds up in the blood. High hormone level in the blood means that EITHER the thyroid has been producing a smaller amount of excess hormone that's been building up in the blood over a longer period of time, OR the thyroid's been producing a lot of excess hormone that's been building up in the blood over a shorter period of time. Bloodwork can't tell you how much excess the thyroid is producing how quickly.

Methimazole has no direct effect on excess thyroid hormone in the blood. What methimazole DOES do is restrict the amount of new hormone that the thyroid produces. Once the methimazole dose reaches a level where the thyroid is no longer producing excess hormone, then the body will start using and eliminating the excess hormone from the blood. It's a gradual process, and not one that should be rushed by overdosing methimazole (which can be fatal).

Regina, call your vet and ask these questions:

1) What type of thyroid test was run?

2) What was the exact result, and what is the lab's reference range?

Once you have the answers to those two questions, please post them here. That'll give us a better idea of your cat's current condition.

We have seen cats here on the Cat Forum who have had lethal and near-lethal reactions to high starting doses of methimazole, so don't let your vet talk you into it. You have no obligation to keep your vet happy. Your obligation, as you clearly already know, is to safeguard and promote your cat's health. Stick with the "start low and go slow" approach to methimazole dosing. Give no more than 2.5 mg twice daily to start, and retest thyroid in 3 weeks. Depending on the results of the retest, you should either increase or decrease dosage slightly (by 1.25 mg daily either way, with the larger dose being in the a.m., if the doses are uneven), or hold steady if euthyroid (normal thyroid level) has been achieved. It'll probably take a while for your cat to safely and slowly reach euthyroid, during which time you should retest and adjust med dosage every 3 weeks. That's how you keep your cat safe during methimazole med regulation.

Laurie


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## ~*Regina*~ (Apr 16, 2008)

Sorry it took so long, I just got her paperwork today. This is what they gave me, looks like it was a T4 test.


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## doodlebug (May 13, 2006)

What...I don't get it? Her value is 2.5 and the normal range is .8-4.0. Why is she on meds for hyper-t? Her value is normal...am I missing something? This is the original test that triggered them to put her on meds right? Where did the vet tech come up with the idea that her number was off the charts?


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## ~*Regina*~ (Apr 16, 2008)

Ya, this is the test... Now I am also confused... Why would they have me give her meds if she is normal? Maybe its because there are a few there that are high?

Im going to the radiologist tomorrow with Tessie so I will ask them what they think.... If they say she doesnt have HyperT I am changing vets.

Poor Tessie has been so moody too, I sware it's from the pills...


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## laurief (Jun 22, 2008)

Someone screwed up big time! Either they gave you the wrong lab results, or the vet got your cat's lab results mixed up with another cat's when she read them, or the vet completely misinterpreted the results. If these are, indeed, your own cat's lab results that initially diagnosed hyperT (and not follow-up bloodwork that was run after you had already been giving methimazole for a while), then you need to stop giving methimazole immediately and contact your vet first thing in the morning.

Laurie


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## laurief (Jun 22, 2008)

Elevated albumin is an insignificant finding. If you fed your cat within 12 hrs prior to the blood draw, that could account for the elevated triglycerides. If, however, your cat was fasted for 12 hrs prior to the blood draw, more testing should be done to determine the cause of the elevated triglycerides. The elevated calcium is concerning. That's the only thing in your cat's bloodwork that would have me worried, but it certainly is no reason to be giving methimazole.

Laurie


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## ~*Regina*~ (Apr 16, 2008)

No, she did not fast before the blood test.
This is a note that was on the bottom of the paper, didnt know if it meant anything...







I will be calling the vet in the morning!

Tessie has Cancer, could that be why her calcium is up? She had this blood taken before the tumor was removed.


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## doodlebug (May 13, 2006)

~*Regina*~ said:


> Im going to the radiologist tomorrow with Tessie so I will ask them what they think.... If they say she doesnt have HyperT I am changing vets.


The radiologist will look at these numbers and say she doesn't have hyper-t. Diagnosing hyper-t is pretty straight forward unless the T4 number is hovering near the upper limit, but then it requires additional tests that are not part of a standard blood chemistry. You need to get back to your vet and ask them the hard questions. I find it unsettling that there is no identifying info these lab results (or did you take it off being publishing it here?). 

And if they screwed this up, you have to wonder about the cancer diagnosis...


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## cat owner again (Dec 14, 2012)

You are all more knowledgeable. All I know is don't hesitate to question a doctor or vet when you can see that it is not right. My dog is 6 pounds and was on a lot of medication at one time. The first time I went with the dose, it was pretty awful - like a bad drug trip. I adjusted the meds and since my dog was regulated and better, my vet recorded my dosage amounts in his chart. My vet also said my dog needed thyroid medicine - what for? He shows no symptoms that I could read about anywhere. He is 15 years old. The less medicine the better to keep him alive. If he had all the medicine that was recommended in his old age, I shudder to think if he would still be alive. My mom is 96 and the same goes for her. I am not saying it is not necessary but all medicines have side effects in the body. We have to be careful.


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## ~*Regina*~ (Apr 16, 2008)

They did 2 blood tests, a senior panel and then later the T4. The only thing I cut off was my information from the paper. The funny thing is she doesnt show and symptoms of having HyperT... She has stayed the same weight for years now, beautiful coat and full of energy.

The cancer diagnosis is right, I have the paper work for that as well, let me see if I can get a good picture of it.


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## doodlebug (May 13, 2006)

In the article below, Dr. Petersen is recommending that hyper-t cats be given a methimazole dose that keeps them in the 1.5-2.5 zone. Since your cat is already in that range, albeit on the upper limit, it doesn't make any sense that the vet would want to treat it at this point. Especially with 5 mg twice a day. If it were me, I would just have it checked again in a few months. 

Animal Endocrine Clinic: How to Dose and Monitor Hyperthyroid Cats on Methimazole


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## laurief (Jun 22, 2008)

OK, here's what the notes mean at the bottom. Elevated calcium MAY indicate cancer, but it can occur for other reasons, as well. How was your cat's cancer diagnosed? If it is, indeed, an accurate diagnosis, then yes, it may possibly account for the elevated calcium (depending on the type of cancer). Was a pathology performed on the tumor after it was removed, and do you have a copy of the pathology report?

A Total T4 above mid-range is considered to be in the gray zone where hyperT is still a possible diagnosis. Mid-range in your cat's case is 2.4, and your cat is just over that at 2.5. If you want to definitively rule out hyperT, you would need additional blood testing of the thyroid. The note on the lab results mentions FT4ED (Free T4 by Equilibrium Dialysis), which is a different thyroid blood test that is often used to help clarify the status of the thyroid.

Laurie


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## ~*Regina*~ (Apr 16, 2008)

Thanks Laurie and Doodlebug!
I think I may just do what you said and stop giving the pills and have her blood done again in a few months. I will still call the vet in the AM to find out why she needs these pills. She has an appointment in 3 weeks to have another T4 test, i'll keep it for now but will cancel if no more pills are used.


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## laurief (Jun 22, 2008)

~*Regina*~ said:


> They did 2 blood tests, a senior panel and then later the T4. The only thing I cut off was my information from the paper. The funny thing is she doesnt show and symptoms of having HyperT... She has stayed the same weight for years now, beautiful coat and full of energy.
> 
> The cancer diagnosis is right, I have the paper work for that as well, let me see if I can get a good picture of it.


So, the Total T4 results on the same page as the Super Chem and CBC was not part of the senior panel? Or are you saying that the T4 was tested twice, once with the senior panel, and a second time separately? If it was tested a second time separately, do you have those results, as well?


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## ~*Regina*~ (Apr 16, 2008)

Here you go, the paper work on the cancer.
Top







bottom


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## laurief (Jun 22, 2008)

If you want clarity on all of this, stop giving her methimazole, wait a month or two, then have both a Total T4 and a Free T4 by Equilibrium Dialysis run. Also, have a 12 hr fasting triglyceride test run to see if her triglycerides are really that high, or if it was just a result of a non-fasted blood sample. If a fasted sample comes back with triglycerides that high again, then further testing would be warranted.


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## ~*Regina*~ (Apr 16, 2008)

laurief said:


> So, the Total T4 results on the same page as the Super Chem and CBC was not part of the senior panel? Or are you saying that the T4 was tested twice, once with the senior panel, and a second time separately? If it was tested a second time separately, do you have those results, as well?


This is all the vet office gave me. The senior panel was first because I brought her in to the vet because of the tumor. Then 2 days later they called me and said something was elivated (cant remember exactly what) and wanted to do the T4 test (They used the same blood for both tests).


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## ~*Regina*~ (Apr 16, 2008)

laurief said:


> If you want clarity on all of this, stop giving her methimazole, wait a month or two, then have both a Total T4 and a Free T4 by Equilibrium Dialysis run. Also, have a 12 hr fasting triglyceride test run to see if her triglycerides are really that high, or if it was just a result of a non-fasted blood sample. If a fasted sample comes back with triglycerides that high again, then further testing would be warranted.


Sounds like a plan, thanks!

question... are you a vet? You seem to know your stuff


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## laurief (Jun 22, 2008)

Nope, not a vet. Just Mom to lots of kitties with lots of illnesses over the last several decades and an insatiable interest in researching my cat's various illnesses.


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## laurief (Jun 22, 2008)

OK, so when you talk to your vet tomorrow, you need to clarify exactly how many thyroid tests were run on that same blood sample, which types of thyroid tests were run, and the results of all thyroid tests (if more than one was run).


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## doodlebug (May 13, 2006)

I would also clarify why they went straight to medication without doing the Free T4 test, and at such a high dose level.


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## ~*Regina*~ (Apr 16, 2008)

OK, so I can make sure I don't sound stupiud when I call...
There should have been 2 additional tests done when they saw levels were high on the senior panel (the Total T4 and the Free T4)?
Im going to ask the vet why the Total T4 was not done and why she is on meds when she is normal and shows no signs of having HyperT.
You both are fantastic, Thank you!


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## ~*Regina*~ (Apr 16, 2008)

I just decided after reading this post over and looking things up online that I am going to stop giving her the pills and at her 3 weeks appointment have the free T4 test done. I will call them today and let them know I am stopping the pill and would like a new bloodtest done while she fasted for 12hrs. If they start to question me I will just say everything we talked about here, I mean what is 3 more weeks right? If it wasnt for me bringing her in for the tumor, blood wouldnt have been taken and I would not be having this issue...
I am also going to ask the vets opinion today and see what they think... 2 opinions are always better then 1.


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## laurief (Jun 22, 2008)

OK, this thread got so busy for a while there yesterday that I think there was some overlap and confusion, so let me try to get it all straightened out before you call your vet.

You mentioned (I think) that your vet ran BOTH a senior panel AND later, a thyroid test using the same blood sample. My question was whether the senior panel included a Total T4 (as seems to be the case with the lab report you posted), and if so, does that mean that TWO thyroid tests were run on that same pre-methimazole blood sample (the Total T4 in the senior panel, and a second T4 test run later)? Or has there only been ONE T4 test run so far? That's what I'm confused about.

In any event, this is what we know for sure based on the information you provided in this thread. There has been at least ONE Total T4 test run that had a T4 blood value in the "grey zone", diagnostically speaking. 

For some unknown reason, your vet diagnosed your cat as hyperT and prescribed a dangerously high starting dose of methimazole, which you administered at least once. I am unclear on how much or how long you have continued to give methimazole to your cat.

NO follow-up thyroid testing has been performed since starting methimazole.

So, here's where we are now. You have decided, starting today, to stop giving your cat methimazole at any dose. 

Your cat needs additional thyroid testing to clarify her thyroid status, but this testing must NOT be performed until ALL trace of methimazole and its effects have left her body. To this end, you should wait 3 full weeks after stopping methimazole before having new thyroid tests run to make sure you get accurate results NOT influenced by the methimazole you've already given her.

The standard diagnostic test for hyperthyroidism is the Total T4, which is the test in which your cat came back in the "grey zone". There are a number of other thyroid tests that can be used to help clarify a hyperT diagnosis, including a full thyroid panel (Total T4, Free T4, Total T3, and Free T3), a FT4ED (Free T4 by Equilibrium Dialysis), and others. It's important when discussing these tests to be very specific and use the full name of each test, since, for instance, a Free T4 is NOT the same test as a FT4ED. If you're up for it, the following link is to a blog written by a highly respected veterinary endocrinologist, Dr. Mark E. Peterson. It will provide you with enough information about hyperT diagnostic testing to explode your brain: Animal Endocrine Clinic: Confirming the Diagnosis of Hyperthyroidism in Cats: Serum T4 Concentrations

I strongly recommend you call Dr. Peterson's clinic at (212) 362-2650 and ask them which diagnostic tests they recommend under these circumstances to clarify your cat's thyroid status. When in doubt, a specialist's opinion is invaluable.

Laurie


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## ~*Regina*~ (Apr 16, 2008)

Talked to the other vet today. She said I should not have her on these pills and to do exactly what you said and do a new fasted free T4 blood test in 3 weeks to get a better result.
I will be calling my other vet in the AM to let them know.
Thank you for all the help!


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## laurief (Jun 22, 2008)

Sounds like you should be sticking with the vet you spoke to this morning. I, personally, wouldn't trust the vet who prescribed the methimazole as far as I could throw them.

Laurie


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## ~*Regina*~ (Apr 16, 2008)

So the vet was right about the HyperT, she definantly has it. They did do a Free T4 and that showed that she was very high (I saw it tonight). So Tessie is back on the pills and we will be checking her blood in 3 weeks to make sure she is on the right dose.
So false alarm.... Thank you all for your help!


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## cat owner again (Dec 14, 2012)

I wish you a lot of success with that. You are a good mom.


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