Methimazole
“This page provides important general information for pet owners whose animals have been prescribed Methimazole during a consultation by Dr Noor. Methimazole for pets is provided here as general educational information.”
Key Information on Methimazole for pets
Important note: This handout is meant to address common questions. It does not include every detail that exists about this medicine. It also does not replace guidance from your veterinary care team.
- This medicine is used to lower thyroid levels when they are too high (this problem is called hyperthyroidism, meaning the thyroid is overactive).
- It is most often given by mouth as a tablet or a liquid. For some animals that cannot handle oral tablets or liquids, a gel can be specially made to rub on the skin.
- Changes in your animal’s signs may not be seen right away. Improvement can take a few weeks.
- Your animal will need blood tests while taking this medicine. These checkups are important. Do not skip them.
- Side effects that are often seen include throwing up, loose stool, eating less, or acting tired.
- If you are pregnant, breastfeeding, or trying to become pregnant, wear gloves or do not handle this medicine.
- Wear gloves when you handle animal waste from a treated animal, when you touch tablets that are broken or damp, when you give the liquid by mouth or apply the gel, or if you have low thyroid levels.
- After you handle this medicine, wash your hands.
Description
- This is a medicine that reduces thyroid activity (an “anti-thyroid” medicine).
- It comes as tablets, sugar-coated tablets, and a liquid taken by mouth.
- Gel forms can be specially prepared so the medicine can be placed on the skin and absorbed through it (this is called transdermal, meaning “through the skin”).
Other common names
- Felanorm
- Felimazole
- Tapazole
Uses
Approved uses in animals:
- Used to treat high thyroid levels (hyperthyroidism) in cats.
Your veterinarian may also choose to use this medicine in other animal species or for other purposes.
Before this medication is given
No medicine is completely safe for every patient. Talk with your veterinarian about:
- Any other medicines or supplements your animal is using.
- Any health problems your animal has now or has had before.
- Any bad reactions your animal has had to medicines in the past.
- The possible risks of using this medicine if your animal is pregnant or nursing.
Warnings for animals
Do not use in animals:
- That have an allergy to this medicine.
- That have an allergy to carbimazole or polyethylene glycol.
- That have an immune system disease where the body attacks itself (an autoimmune disease).
- That have blood problems, such as low red blood cells (anemia), low platelets, or problems with blood clotting.
- That have kidney failure.
- That are pregnant or nursing.
Use with caution in animals:
- That have liver disease or kidney disease.
Some animal competitions do not allow certain medicines. If your animal competes, check the rules while your animal is taking this medicine.
Warnings for humans
Wear gloves when handling:
- Waste from treated animals, including litter, stool, urine, and vomit.
- Tablets that are broken or damp.
- The liquid form or gel forms that go on the skin.
- If you have low thyroid levels.
If you are pregnant, breastfeeding, or trying to become pregnant, wear gloves or avoid handling this medicine.
After handling, wash your hands with soap and water.
The liquid form can irritate skin and eyes. If it gets on skin, wash the area right away. If it gets in the eyes, rinse the eyes right away with water and contact a physician if irritation happens.
How do I give this medication?
Give this medicine exactly the way your veterinarian prescribed it.
- You may give it with food or without food.
- Putting tablets into food may help cover up the bitter taste.
- Do not break or crush sugar-coated tablets.
- For liquids, use only the dosing syringe that is provided.
When using a gel that is applied to the skin:
- Put the dose on the inside of the ear flap (pinna).
- Before the next dose, wipe away any dried or crusted medicine that is still there.
- Switch ears each time you apply it.
- Do not use the gel if it looks like it has separated.
Side effects
Common — contact your veterinarian if these problems are strong, keep happening, or get worse over time:
- Vomiting, diarrhea, or eating less.
- More vocalizing than usual.
- Low energy.
Severe — stop giving the medicine and contact your veterinarian right away if you notice any of the following:
- Not eating at all.
- Bruising or other signs of bleeding.
- Very low energy or weakness.
- Yellow color of the skin, gums, or the whites of the eyes (jaundice).
- Bleeding caused by intense itching and scratching, usually on the face.
How will I know it's working?
This medicine must be given regularly for several weeks before it reaches its full effect.
As it becomes fully effective, you should notice your animal’s signs slowly improving.
Side effects may still appear right away.
Your veterinarian will need follow-up tests to check how well your animal is handling this medicine and to see how well it is working.
If your animal’s signs get worse or do not improve, contact your veterinary clinic.
How long will the medication effects last?
After the last dose, this medicine will no longer work within 24 hours.
How long do I give it for?
This medicine may be used for different time periods. Often it is used for life. Sometimes it is used only for a short time until the thyroid gland is removed by surgery or treated with radiation.
Give it for the length of time your veterinarian instructs.
Refill the prescription on time so treatment is not interrupted.
Overdose
If you see an overdose happen, or you think one may have happened, contact your veterinarian right away.
If possible, have the product or the label with you.
Missed dose
In most situations, if you forget a dose:
- Give it as soon as you remember, and then go back to the normal schedule.
- If it is almost time for the next dose, do not give the missed dose.
- Give the next dose at the usual time.
- Continue the normal schedule.
If you are not sure what to do, call your veterinary clinic. Do not give two doses at once and do not give extra doses.
Storage
- Keep in the original container at room temperature.
- Keep away from light.
- Store where children and animals cannot reach it.
Disposal
Do not put this medicine into the toilet and do not pour it into a sink.
Ways to get rid of unused or expired medicine include:
- Medication take-back locations: This is the best option when available. To find a nearby location, contact local law enforcement or your waste management office.
- At-home disposal: Put it in the regular household trash.
Do not keep leftover medicine for later use and do not give it to anyone else.
Questions?
Speak with your veterinarian.
“Disclaimer: The information on this page is provided as general educational material only. Every animal’s health situation is unique, and treatment decisions must be based on a full veterinary assessment. Always follow the specific instructions given during your consultation, and contact the prescribing veterinarian if you have any concerns.”