PANIC! Wrong dose of Thyronorm for hyperthyroid cat.

[BrainInAJar]

Hi everyone. BIT OF A PANIC TONIGHT! I think I've been giving my cat completely the wrong dose of Thyronorm.

I was told her thyroid was "sky high" in November. I was told to give her 5mg/day which is 1ml, divided into 2 doses per day. I did this for 4 weeks (or so I thought).

I was then told to increase it to 0.75ml twice a day. So that would be 7.5mg. She had another blood test 2 weeks after that and I was told her thyroid was now 30 which was right in the middle of the normal range. So all fine, just continue as we are.

HOWEVER it is only today that I have noticed the syringe that I've been using to give her it (which is branded "Thyronorm") has both ML and MG marked on it. I have only been giving her 0.5mg twice a day and then 0.75mg twice a day. So 1/10 of what it should have been.

But then how the hell has her thyroid normalised then?

Any help appreciated.

Sorry, I think I've been giving her 1/5 of what it should have been.

I was giving her 0.5mg twice a day when it should have been 2.5mg twice a day.

And then 0.75mg twice a day when it should have been 3.75mg twice a day.

Well fortunately it would seem that's the correct dose

But how did you not have too much left over? Has the vet not noticed you didn't need a refill?

That's the strange thing! It was various different vets involved though in the various consultations so maybe that's why they didn't notice I didn't ask for a repeat prescription.

That's why I've twigged it today - now that she's meant to be on the 1.5ml/day it's obvious the 30ml bottle should last exactly 20 days. I opened this bottle 5 days ago and there's barely any gone.

I feel absolutely terrible. Not to be funny though but shouldn't the vet point out to you that there is both mg and ml printed on the syringe and they are not the same thing? I mean it's in tiny print as well. Little old ladies won't see that!

In my vets they go over it with you and the receptionist confirms your understanding before you go

Bloody hell, mg, ml, what a confusing nightmare. Tell the vet, see what they say. Whatever it is you've been giving your cat seems to have worked, so don't worry. Maybe the vet got confused between the mls and the mgs and you've actually been giving the correct dose?!

Looking online the drug manufacturer suggests 5mg/day as a starting dose. But various facebook communities do think that's too high.

So maybe purely by accident I've actually done the right thing by her?!! <tries madly to assauge own guilt>

Yes I mean I highly doubt that I'm the only person to have made this mistake if they don't bloody well point it out to you.

Long term thyronorm user. Those bottles last AGES - I think you’ve been giving the correct dose. Is it a very thin syringe?

So the vet prescription for the starting dose was as per the drug manufacturer's recommendation.

It's me who's got confused by misreading the labelling on the syringe.

(mine started on 0.5mg x twice a day, went up to 0.75 x2)
also - you know to order from Pet drugs online, right? The vet will charge you for the prescription (maybe £30 for 3 refills) and you’ll get the medicine itself for half what the vet charges

@Vermin thanks, yes I'm only on my 2nd bottle but assuming she lives a while longer, I was going to switch to buying online.

@Vermin that's interesting. So you were told to give the dose that I've accidentally been giving!

Here is a picture of the syringe. It appears to be a 1ml syringe. So I should have been giving half to 3/4 of a syringe full per dose. When I've only been giving 2-3 drops.

It has lines indicating the mg, going up to 5 and then at the plunger-end it indicates that the 5mg = 1ml.

My cat has half a syringe.

After with a pp. I get a £18 prescription from my vets and from that I can buy 3 prescriptions of the large 100ml bottles. They are about £45

Think it's costs me about £18 a month in total as a bottle last about 3 months.

Now I'm looking back at my records.

I started her on a 30ml bottle on 24 Nov.

On 16 Dec I increased her dose by 50%
I finished the bottle on 15 Jan.

So a 30ml bottle lasted 50 days. But future bottles will last less than 50 days now that she's fully on this increased dose.

The bottle therefore isn't lasting 5 times more than it should.

I wish I knew a bloody mathematician or a chemist or something!

By the way - how are you giving it? It’s mouse flavoured or something delicious so you don’t need to aim it in like a drug - cat will lick off the end as you slowly push the plunger

I just mix it with lick e lix and she wolfs it down. I'm not 100% sure she would tolerate me putting a syringe in her mouth, no matter how delicious it tasted!

Mine takes straight from syringe as well - she loves it and comes running when she sees syringe.

They changed the syringes a little while ago, assume because it was confusing. The new syringes are marked in mg only and the instructions on the bottle should be given in mg so hopefully no room for error going forward - check the syringe when u get your next bottle

I'm looking at a facebook group and there are lots of posts there saying that the recommended starting dose is way too high anyway and that the advice to vets should be changed.

Don’t feel bad, at least you didn’t overdose her. I know exactly the syringes you mean and they are ridiculous, I got my vet to draw a marker pen line on it to stop me getting confused when we started thyronorm.

Glad you cat is normalising.

With hyperthyroidism it is possible for a careful cat owner to work out the exact dose needed by observing the cat’s behaviour. If cat is manic and constantly asking for food, cat needs a higher dose. If cat is sleeping loads and putting on weight and has low energy, the dose is probably too high. My cat was super high risk for heart attack and terrified of vet so I refused to do the frequent blood tests as it was likely the blood test procedure would kill him off. But when I eventually did allow one test after some months of me slightly adjusting his dose based on my observations, the vet was startled to discover that his dose was perfect :)

So do get in the habit of observing your cat’s energy levels weight and appetite and that will tell you a great deal about whether the dose is correct.

Thanks. She seems ok in herself. Not hyper. Mostly eats, sleeps and enjoys a cuddle. The early morning yowling stopped with days even on the (accidentally) tiny starter dose.

She is 3.35kg. Thin. But her weight doesnt appear to be decreasing. I have special scales at home for weighing babies/pets.

Cats are individual so yes there are some cats that the standard starting dose is too much, but others where it is not nearly enough.
I would say of the cats I start on thyronorm 60% need their dose increased at the first blood tests, 35% need it decreased and 5% it's just right.
Either way your cat what ever you are doing is right, but at your next appointment show the vet on the thyronorm syringe exactly what giving so they can put the right information in her notes.

You know the other weird thing? She had a severe vomiting episode 3 weeks in, when still on the tiny dose. She had an emergency appointment and was giving medication and fluids.

Maybe that would have been worse if I'd started her on the higher dose. Not clear if the vomiting was caused by the thyroid or the medication.

You're not alone, OP. Don't worry.

I mistakenly gave mine 5mg for his first and second dose. When I spoke to the vet later in the day she told me it should have been 0.5mg. I was horrified, but cat was ok 😱

The following day a different vet in the same practice rang to tell me the first vet had made a mistake, and the dose should have been 2.5mg, not 0.5.

In the same conversation she told me that sometimes the syringes are measured in ml and other times in mg, which is clearly lunacy. She said they always check that their meds go out with a mg syringe, as that's how the dose is described on the box.