Methimazole for Cats - Dosage, Uses and Side Effects

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In this AnimalWised article we are going to talk about methimazole for cats, a drug that veterinarians prescribe for cats suffering from hyperthyroidism. This disease that affects the thyroid gland can only be diagnosed by the veterinarian and, of course, only this professional is responsible for prescribing this drug and telling us what dosage is appropriate. On the other hand, cats that consume methimazole have to undergo strict veterinary monitoring.

Read on to find out what exactly this drug is, what is methimazole for cats for and what are its possible side effects.

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  1. What is methimazole?
  2. What is methimazole for cats good for??
  3. Methimazole dosage for cats
  4. Contraindications of methimazole for cats
  5. Side effects of methimazole for cats

What is methimazole?

Methimazole or thiamazole is a derivative of thionamide and belongs to the pharmacotherapeutic group of antithyroid preparations. This name already allows us to anticipate its function, which is none other than the treatment of hyperthyroidism, a disease in which the thyroid gland produces a higher quantity of hormones than normal. Thus, methimazole works by blocking the synthesis of these hormones. Specifically, in 1-3 weeks it reduces the T4 values. Methimazole for cats is a rapidly absorbed drug that is mainly eliminated in the urine..

What is methimazole for cats good for??

The indication for using this medicine is clear: hyperthyroidism. If our cat is diagnosed with this disease, the veterinarian will prescribe methimazole in any of the following cases:

  • Stabilize thyroidism before proceeding with the removal of the thyroid gland.
  • Treat hyperthyroidism long-term, but you have to know that the disease is not cured, only the state of the cat is controlled. For this reason, other options are considered, such as surgical thyroidectomy or treatment with iodine..

It should be noted that hyperthyroidism is more common in elderly cats, is due to benign or malignant thyroid disorders and usually presents in a more or less severe way. A marked weight loss, accompanied by an increase in appetite and thirst, hyperactivity, tachycardia, bad appearance of the coat, diarrhea or vomiting are signs that should make us go to the vet. In addition, in cats over seven years of age, veterinary check-ups are recommended at least annually, precisely to detect this type of disease early..

Methimazole dosage for cats

We found several formats of methimazole in coated tablets and oral solution, so we can choose according to the presentation best tolerated by our cat. Both to stabilize it before surgical thyroidectomy and for the treatment of long-term hyperthyroidism, the starting dose will be the same, that is, about 5 mg daily.

It is recommended to give methimazole to the cat with food and divide the dose in two doses, one in the morning and one in the afternoon, although it can also be administered in a single dose. However, this starting dose is indicative. Only the vet can decide how much methimazole our cat needs. Always try to give the lowest dose that achieves the desired effect. In any case, more than 20 mg per day is never prescribed. There is also transdermal methimazole, which is a good option for cats that do not accept drugs orally or cause digestive discomfort. You just have to apply it to the inner area of ​​the ear. Discover in this other article How to give medicine to a cat.

Cats treated with methimazole should have access to sufficient amount of water 24 hours a day, as this drug can cause blood concentration, so they have to be well hydrated. If it is always important to give our cat only drugs prescribed by the veterinarian, in the case of methimazole it is crucial. In fact, depending on the dose that is prescribed, the cat will have to be monitored and it will always be necessary to carry out regular blood tests..

In addition, before starting treatment, a blood test that includes the measurement of total serum hormone T4 must also be done. The dose is adjusted according to the result of this parameter and its evolution when following the treatment..

Contraindications of methimazole for cats

There are some cats for whom methimazole is not recommended. They are the ones who are in these situations:

  • Systemic diseases such as diabetes or liver failure.
  • Autoimmune diseases.
  • Alterations in white blood cells.
  • Platelet abnormalities or clotting problems.
  • Gestation and lactation.
  • If the cat is taking any other medication and the veterinarian does not know it, it must be reported to ensure that no interactions occur. Vaccines also count.
  • Of course, it is not suitable for cats with an allergy to this active ingredient.

Also, keep in mind that some other cats, such as those with kidney disease, will only be able to use methimazole once the veterinarian carefully weighs the pros and cons of both administering the drug and not administering it. This is because methimazole reduces glomerular filtration, hence, if it is decided to medicate, it is essential to subject the cat to strict control of its kidney function.

Side effects of methimazole for cats

First of all, if we notice discomfort in the cat or fever, we must immediately notify the vet. In these cases, it is necessary to do a blood test for hematological and biochemical analysis. If a problem is diagnosed, the vet will prescribe the appropriate medication to control it..

On the other hand, adverse effects have been reported after the administration of methimazole in cats, although they are usually mild and resolve spontaneously without the need to stop treatment. In the cases in which these are more serious, it will be necessary to suspend the medication. However, adverse reactions are considered to be rare. These include the following:

  • Vomiting.
  • Decreased or loss of appetite.
  • Lethargy.
  • Intense itching.
  • Irritations in the head and neck area.
  • Eruptions.
  • Jaundice, which is the yellowing of skin and mucous membranes. It is associated with a liver problem.
  • Hematologic abnormalities.
  • If a high dose is administered, in addition to these signs, the cat may suffer hypothyroidism, although it is infrequent.

This article is merely informative, at we do not have the power to prescribe veterinary treatments or make any type of diagnosis. We invite you to take your pet to the vet in the event that it presents any type of condition or discomfort.

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