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  • Best Friend Family Vet
  • Doley Road,
  • Byford,
  • Western Australia,
  • Phone: (040) 735-2836

Thiamazole/Methimazole

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medicationWhy has my veterinary surgeon prescribed this medicine?

Thiamazole (also called methimazole) is an antithyroid drug that acts by blocking the production of thyroid hormones. It is used in cats that have an overactive thyroid gland (feline hyperthyroid) to reduce the level of thyroid hormones. Your veterinary surgeon may prescribe this medication before surgery to remove the thyroid gland.

How do I give this medication?

- This medication is given by mouth.

- Give this medication to your pet as directed by your veterinary surgeon. 

- READ THE LABEL CAREFULLY.

- Try to give this medication at about the same time(s) each day.

- DO NOT give the pet more medicine than directed and DO NOT give the medicine more often than directed.

- Try not to miss giving any doses.

- Wash your hands after giving the medication.

What if I miss giving a dose?

Give the dose as soon as possible. If it is almost time for the next dose, skip the missed dose, and continue with the regular schedule. Do not give your pet two doses at once.

How do I store this medicine?

- Keep this medicine out of reach of children.

- Store this medicine in a cool, dry place at room temperature. Store away from heat and direct sunlight.

Potential side effects

- Side effects have been reported including lack of appetite, vomiting, lethargy, and scratching.

- Tell your veterinary surgeon if your pet is diabetic or you think your pet may be pregnant.

- Your veterinary surgeon may need to monitor your pet's blood to check liver function.

- Other side effects may occur. If you notice anything unusual, contact your veterinary surgeon.

Possible drug interactions

- Make sure to tell your veterinary surgeon what other medication including wormers you are giving to your pet.

- Contact your veterinary surgeon if your pet experiences any unusual reactions when different medications are given together.

© Copyright 2025 LifeLearn Inc. Used and/or modified with permission under license. This content written by LifeLearn Animal Health (LifeLearn Inc.) is licensed to this practice for the personal use of our clients. Any copying, printing or further distribution is prohibited without the express written consent of LifeLearn. This content does not contain all available information for any referenced medications and has not been reviewed by the FDA Center for Veterinary Medicine, or Health Canada Veterinary Drugs Directorate. This content may help answer commonly asked questions, but is not a substitute for medical advice, or a proper consultation and/or clinical examination of your pet by a veterinarian. Please contact your veterinarian if you have any questions or concerns about your pet’s health. Created on Aug 2, 2015.