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Drhollowayvet
Drhollowayvet,
Category: Cat Veterinary
Satisfied Customers: 755
Experience:  Relief Veterinarian at Aloha Animal Hospital
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One of my cats that has been staying at my mom's has

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One of my cats that has been staying at my mom's has been exhibiting strange behaviour. Lost of scratching and grooming herself like as if she is itchy. Licking her lips like as if there is nausea. Slight 3rd eyelid visible. Not as playful as usual. And occasional reaction like trying to throw up hairball. After much thought, I asked my mom if it is possible she ate the hyperthyroid medication - methimazole - that my mom puts out for her cat in a pill pocket. She said she didnt think so - but could not be sure. What do you think? Does this sound like potential side effects? Is there further potential damage that could result? How long would it take to clear the system so that one could say that this might have been it?
Submitted: 9 months ago.
Category: Cat Veterinary
Expert:  Drhollowayvet replied 9 months ago.

Hello this is Dr. Holloway but you can call me Dr. H for short.

Sorry to hear about your kitty! The symptoms that you describe are definitely possible with an acute (sudden) Methimazole adverse reaction. And it is possible that the dose she got was way above what would be considered a safe dose, so there is a potential toxicity here from overdose.

These symptoms are considered to be rare yet serious adverse effects from Methimazole and therefore I would recommend taking kitty in to see a vet for a complete exam and possible detoxification: induced vomiting (if she ingested within the last 2 hrs), activated charcoal (to absorb any more of the pill still in the system, and supportive care.

- Dr. H

Customer: replied 9 months ago.
These symptoms have been going on for about 3 days. So I don't think it would be acute. The does was 5 mg. But it is possible that she ingested it a couple of times. How long would it take for it to leave her system?
Expert:  Drhollowayvet replied 9 months ago.

Half life (how long it takes for half the med to leave the body system) for Methimazole is 2-10hrs.

Oh ok. Yes multiple doses worry me. About how big is kitty?

Customer: replied 9 months ago.
She is small still. She is about 10 months. She seems a little better today than yesterday - a little more playful. But lots of licking and scratching. So being that she is smaller - could take at least a day or more for it to leave her system? Any potential damage to her system? I mean it can't be the worst stuff in the world if the other cat is taking it daily.
Expert:  Drhollowayvet replied 9 months ago.

An overdose is an overdose no matter what the medication is. Plus Methimazole can have adverse effects in some cats and none in others. Systems that can be affected are the liver, it can cause anemia (low RBC count), low platelets, and of course the pruritis (itching). All considered rare but potentially dangerous side effects especially if the dose was too high for her.

Most cats are treated with 2.5 mg every 12 hrs. But in young kittens even this dose can be too high because her liver and organs are still maturing.

- Dr. H

Expert:  Drhollowayvet replied 9 months ago.

I do hope that she is ok. But this is something we know can cause issues in cats. It is best to be safe than sorry. - Dr. H

Expert:  Drhollowayvet replied 9 months ago.

Do you have any more questions or concerns for me to address for your kitty?

Expert:  Drhollowayvet replied 9 months ago.

For the itching you can give a 1/8th-1/4th Benadryl tablet to help with pruritis (itching), however I would still recommend getting her seen as soon as possible.

If you have further questions or concerns for me at this time, I would ask that you please give me a rating by clicking on the "Rate my Expert" button at the top of the screen so that I may receive credit for assisting you with your pet question today. I do hope your kitty feels better soon.

Best regards,

Dr. H

Customer: replied 9 months ago.
Okay - I have contacted our vet. However, she may not be able to come see her until Monday. I'm just curious though - if one cat can handle this on a daily basis - why would the other one be in such danger?
Customer: replied 9 months ago.
Is there anything I can do to protect the organs in the meantime? Again - at this point I don't even know for sure that she did eat one - I am just guessing based on the symptoms. If she comes out of this okay, is there any reason to think there will be long term effects?
Expert:  Drhollowayvet replied 9 months ago.

I cant really answer the question of long term effects, that would best be answered with bloodwork to look at organ function.

There is no antidote that you can give at home for this. The best thing is to avoid exposure of the medication to the kitty and also you can check for other not so emergency situations that could be present such as fleas. That is just about the only other thing that could cause these types of symptoms in a young kitten. However I would not expect just fleas to cause nausea, it is just unheard of.

I am unsure how else to explain that one pet at a recommended tolerable dose of medication can be ok and another at a higher dose of the same medication can be too much for the body to handle. Ok so maybe this will help. It is as to say that one person can handle Penicillin and another person can have a severe allergic response that can put them in the hospital. Does that explain it better?

- Dr. H

Customer: replied 9 months ago.
Okay - one last question - could i mix some activated charcoal with her food?
Expert:  Drhollowayvet replied 9 months ago.

Yes you sure can. As long as it is the recommended dosage of 1-4 g/kg, given once

Expert:  Drhollowayvet replied 9 months ago.

Some pets don't like the taste however, so a syringe helps, but you have to be very careful not to cause aspiration into the trachea.

Customer: replied 9 months ago.
if it has been more than 24hrs since she ingested the pill - will the activated charcoal still help?
Expert:  Drhollowayvet replied 9 months ago.

If it has been more than 24 hrs, it is unlikely it will help any. Typically it has to be given within 2 hrs, 4 hrs at most.

Expert:  Drhollowayvet replied 9 months ago.

Most of what she ingests is completely absorbed and pushed out the other end by 6-8 hrs (GI transit time)

Expert:  Drhollowayvet replied 9 months ago.

Hopefully she comes out ok and rids the medicine out of her system without long term effects. However, if she does not improve soon I would recommend a vet visit for the very least a thorough exam to make sure everything looks and sounds ok.

- Dr. H

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