Methimazole for Cats

Methimazole for cats is widely used for hyperthyroidism. Hyperthyroidism often affects older cats and the condition can be treated with surgery, by removing the hyperactive thyroid glands or through medication treatment. Methimazole is typically a safe type of treatment, but in most cases, it will be needed for life, as the drug will only reduce the production of thyroid hormones as long as it is administered.

Methimazole for Cats

Methimazole is also known as Tapazole and it is very commonly used in cats that have hyperactive thyroid glands.

Methimazole is a chemical that is employed in the drug marketed as Tapazole. The substance will inhibit the activity of the thyroid hormones (T4 and T3). When these hormones are produced in excess, the cat will present symptoms such as hyperactivity, increased thirst, acne or poor skin and coat condition.

Tapazole is presently the most widely used hyperthyroidism medication, but in the past, propylthiouracil or PTU was more frequently used. Tapazole has been found to have fewer side effects and basically the same effects as PTU, so it is preferred.

Methimazole is the least expensive treatment option when compared to surgery or radiation therapy. The drug is easy to administer, but the treatment is often lengthy or may even be needed for life, as the drug won’t heal the cat, but will manage the production of thyroid hormones.

Methimazole Dosage

Methimazole can be used orally and in rare cases, as a topical treatment.

The dosage of methimazole should be established by the vet and this can depend on the size and the condition of the pet.

While under treatment with Tapazole, the cat will have to be carefully monitored so that the dosage can be adjusted as needed.

Methimazole Side Effects

The side effects of Tapazole are less serious than the previously used medications for hyperthyroidism (PTU). However, there may be some side effects that include:

  • Lack of appetite and weight loss
  • Vomiting and diarrhea
  • Depression and lethargy
  • Low white blood cell count, which can also weaken the cat’s body and result in several secondary diseases
  • An autoimmune disease may also occur
  • Aggressiveness

Typically, the side effects occur as soon as the treatment is started. If there are no side effects during the first 3 months, these may never occur.

If the side effects are severe, the vet will recommend discontinuing the medication and finding a different treatment option. Once the treatment is discontinued, the side effects should also subside.

Radiation Therapy

If you don’t want to continue the medication treatment for life, the vet will recommend radiation therapy once the thyroid hormone levels are at a normal level.

The cat’s condition will be monitored and once the levels of thyroid hormones are normal, the radiation therapy will be scheduled. The radiation therapy can cure hyperthyroidism in felines and only a dose is required.