Radioiodine treatment for hyperthyroidism

[FeebysOwner]

But I did learn one thing in my reading: One site said that cats can become resistant to methimazole after using it for a while, and mine has been on it >2 years.

I had never heard that! Feeby has been on Felimazole (feline specific version) since 10/2020 and I have not raised the dosage by any consequential amount even though it does need to be raised from time to time since the tumor grows and emits an increasing amount of hormones. If the methimazole isn't working as effectively, I would think it would show up with a T-4 test, which it sounds like your cat's level has. That being the case, the vet would likely increase the dose to see if that would bring the T-4 back down again.

 

[Kflowers]

There seems to be a shortage of some of the chemo drugs, and even of amoxicillin and penicillin in the human sector which maybe effecting the Verlainian sector. I hope I'm wrong, or at least, that this temporary

Cancer drug shortages: 14 medicines now in short supply, according to FDA (nbcnews.com)

 

[Furballsmom]

Hi, I'm repeating this post because I think you missed it from earlier/upthread;

Hello - Here's my story, which is intended to give you an idea as to why I'm even mentioning it ....

My angel Poppycat had a compromised liver prior to being diagnosed with Hyperthyroidism so the medicine was not an option, and he was extremely stressed by normal vet visits so at 17 years old, the treatment was out.

We chose the dietary approach of Hills Y/D. Fortunately he liked their kibble, and they also have canned food. I worked out a feeding schedule where he got both wet and dry Y/D and also Weruva which at the time (early to mid last year, 2022) was the only commercial non-vet-scrip-needed food on the market with the lowest iodine levels that meet AAFCO requirements. Many other cat food brands don't pay any attention and their iodine levels can be amazingly, concerningly high.

To me, it's sort of like a fish tank, where if an aquarist's water source has high levels of chloramine, recommendations for water changes to keep the tank water parameters safe and healthy for the fish can be followed, but when that water source is awful (correlating to what the iodine levels might be in the cat food you are feeding her), ammonia is simply being added right back in to the tank and causing all sorts of unintended, bad issues.

In any case, would your vet consider a diet approach instead of the methimazole, rather than the treatment you're currently considering? Controlled hyperthyroidism is certainly an option to consider.

https://www.chewy.com/hills-prescription-diet-yd-thyroid/dp/54583

 

[Antonio65]

But I did learn one thing in my reading: One site said that cats can become resistant to methimazole after using it for a while, and mine has been on it >2 years.

I didn't know that, but I know that many pet parents have to adjust the dosage often during the treatment. In fact, careful vets advise owners to have their cat checked every 5 to 6 weeks to see if the hormone levels need a different dosage.
In my case, over a period of about 10 months we changed the dosage at least 5 times, sometimes a little higher, sometimes a little lower, even down to 0.625 mg twice daily.

Methimazole do not treat the hyperthyroidism, it only helps to keep those hormones under control. The disease worsens, it's degenerative, it can only get worse.
That's why the dosage of methimazole needs upping and this might be seen as a resistance to the med.

The only real treatment is the radio iodine, but it needs to be administered carefully, the reason why the scintigraphy is highly recommended.
My cat had the scintigraphy done on the same day as the treatment, at the same facility, and the result of this allowed the vets to administer the necessary amount of radio iodine, which in my case was 2.2 mCi.

I understand that you have trouble finding a place where they do perform it, in this case I hope they will stick to a low dosage, based on their experience, rather than a high dosage that could get your cat hypo-T.

 

[Antonio65]

There seems to be a shortage of some of the chemo drugs, and even of amoxicillin and penicillin in the human sector which maybe effecting the Verlainian sector. I hope I'm wrong, or at least, that this temporary

Cancer drug shortages: 14 medicines now in short supply, according to FDA (nbcnews.com)

At the shelter we had to treat a cat with Chlorambucil, and the pharmacy told me I was lucky they had a package of those pills available because it seems it is hard to get, and both people and cats can face dire consequences because of this shortage.
Our cat didn't make it, she only used one tablet, now we have 29 spare tablets and there will be someone who is struggling to have it...

 

[Kflowers]

And you'll find them to give it to them.

 

[Antonio65]

It's a registered drug, and I don't think I can just post something on the web to let everybody know that I am going to give a registered drug away. I should ask the vets and see if some of their patients needs it. Before it expires.

 

[FeebysOwner]

There seems to be a shortage of some of the chemo drugs, and even of amoxicillin and penicillin in the human sector which maybe effecting the Verlainian sector. I hope I'm wrong, or at least, that this temporary

To the best of my knowledge radio iodine therapy is not considered chemotherapy. Nonetheless, I did find this on one vet web site (UK based, but assume it is the same for the US as well as many other countries) -
"We are unfortunately unable to accept any new referrals for feline radioactive iodine treatment. In the last 18 months there have been issues with production and supply of radioiodine affecting human and veterinary hospitals alike. Our supplier has announced today that they will stop production of injectable radioiodine at the end of June. At this time there are no alternative manufacturers or suppliers however we are working to investigate alternative solutions for the future, this is likely to take some time."

Now, if other vets would offer this detail to people, it sure would be helpful.

 

[Kflowers]

Antonio65 No, of course not, but you could speak to your vet, who might know someone in need, or have the connections to find someone.

 

[FeebysOwner]

D david68 - In light of the discussions in the last few posts, have you called Carrboro to see if they too have discontinued radio iodine therapy at this time? Might do that and save yourself a trip.

As I asked before the focus on therapy availibility started, has the vet had you increase the Methimazole to see if that would bring the T-4 down? Sometimes, it takes more than one increase to accomplish that.

 

[Antonio65]

Our supplier has announced today that they will stop production of injectable radioiodine at the end of June. At this time there are no alternative manufacturers or suppliers however we are working to investigate alternative solutions for the future, this is likely to take some time."

Because of the very short half-life of the I-131, it's also impossible to stock it at the facilities.
I guess that these facilities have to order it the day before they need to treat a patient.

 

[david68]

To try to answer a lot of these questions and anticipate others:

I'm a former university instructor with a doctorate, so I have a lot of experience with research.

Yes, I have worked closely with my vet to monitor my cat's thyroid levels, and we have increased methimazole dosage several times. Methimazole is simply no longer keeping her T4 levels in the appropriate range. It got to the point where I was giving it to her 3x a day, every 8 hours, but T4 levels are still creeping up.

I have made a very thorough investigation of the availability of nuclear thyroid scintigraphy in the state of North Carolina. No clinic I can find offers it. If you are located in a place that does, that's great for you, but it's not useful to me to keep repeating the same advice as though I'm somehow a negligent cat parent who doesn't get the message and/or doesn't care enough to look very hard. Do you want a list of websites I've checked and phone calls I've made? Are you just trying to make me feel inadequate?

Yes, I have certainly been in contact with the Carrboro RadCats clinic and have an appointment scheduled with them. I have been through the whole timeline with them of having to take my cat off methimazole for 14 days to get a baseline T4 level, and she is being monitored for any problems by my own vet practice. In fact, I have consulted with two of the vets at that practice about her overall case. I have already spent over $2,000 this year on her on various diagnostic tests including echocardiogram, thyroid ultrasound, blood tests, Vimago scan, and dental under anesthesia, plus medication for her oral stomatitis, an unrelated problem.

This is in addition to having been left the primary caretaker for my 93 year-old mother who suffers from memory loss, so I have complete POA for her and have to manage all her doctor's appointments and medications as well, down to having to put her pills in front of her every day to make sure she doesn't forget to take them.

Geriatric medicine, human and feline, is pretty much all I do these days. I posted her just to get some feedback on the whole process, not to have every aspect of my care of my cat questioned.

 

[FeebysOwner]

I think I can safely say that no one here is questioning your abilities and am sorry that anything that was said was worded in a manner that gave you reason to think we were. We never know who knows what, and it is often hard to discern that in the initial posts. I would venture to guess we tend to cover a lot of bases because of that.

I hope you will take my offering/explanation as a gesture of our sincerity and genuine concern and care to help those who reach out to us for input.

 

[neely]

I think I can safely say that no one here is questioning your abilities and am sorry that anything that was said was worded in a manner that gave you reason to think we were. We never know who knows what, and it is often hard to discern that in the initial posts. I would venture to guess we tend to cover a lot of bases because of that.
I hope you will take my offering/explanation as a gesture of our sincerity and genuine concern and care to help those who reach out to us for input.

Well said, I completely agree!

I would like to add that I understand where you're coming from having been in a similar situation, i.e. caring for two elderly parents simultaneously, two young children one of whom was diagnosed with a life threatening illness, a dog on chemo. and a young cat diagnosed with FIP. We are very sympathetic to what you're going through but as FeebysOwner said, we have no way of knowing people's individual situations and are only trying to offer our personal experiences and advice. You have a lot on your plate right now and we wish you the best of luck with your cat's hyperthyroidism treatment. Sending special thoughts and healing vibes.

 

[david68]

Thanks for the replies.

My cat has now been off methimazole for 4 days, and I'm not noticing any major changes in disposition or behavior. Her weight is stable. She might be eating slightly more, but it's hard to tell.

I'm wondering if she has just become resistant to methimazole after 2.5 years of continuous treatment. As I said in a prior post, I read on one site that went into detail about all the ins and outs of hyperthyroidism treatment that methimazole resistance could occur. That same site said that hyperthyroidism could also mask kidney disease, which I hope is not the case.

But it's at least a good sign that I'm not seeing any negative symptoms after ceasing the drug. 10 days to go . . .

 

[neely]

That same site said that hyperthyroidism could also mask kidney disease, which I hope is not the case. But it's at least a good sign that I'm not seeing any negative symptoms after ceasing the drug. 10 days to go . . .

You are exactly correct, hyperthyroidism can mask other health issues, kidney disease being one of them and also high blood pressure. But I'm glad to hear you are not seeing any negative symptoms and fingers crossed it continues.

 

[CoffeyCats]

Cole has an appointment 7/25. No sintigraphy here in SC either. Not thrilled but he is my 3rd HT cat and I know how this goes. Granted he is younger and otherwise healthier than the other 2 so finding some comfort in that. The dx was an incidental finding on a yearly checkup. Methimazole has worked but he is not good about pills and ears didn't go over well either. Did I mention he is a little biter? Ouch! So far so good off meds I guess although his t4 had tripled in the time he had to be off meds for the preliminary labs/x-ray/urine. Who knows what it will be in 3 weeks. Thankfully they are going to retest that before the radioiodine administration.

 

[catmando2]

Yesterday marked the 1 yr anniversary of my cat George getting his I-131 treatment. He had a T4 level check done yesterday (cat hospital where he got treated required follow up tests at different times up to 1 year to monitor how things are coming along). I'm happy to say that is T4 number came back as 2.9. A healthy value.

I've included a before and after picture of him. There is a noticeable difference in weight. Before treatment he was only about 8 lbs (the poor thing). Today, over 12 lbs. He is an over 12 year old cat (but still thinks he's a kitten!).

 

[Antonio65]

George looks so lovely and healthy. I'm so glad to read the treatment was successful!

 

[catmando2]

George looks so lovely and healthy. I'm so glad to read the treatment was successful!

Thank you. He's back to his old loveable self.