Methimazole For Cats: Uses And Side Effects: Methimazole is an oral medication used to treat hyperthyroidism, a condition where the thyroid gland produces too much of the hormone thyroxine. Methimazole works by decreasing the production of thyroid hormone. The generic name is methimazole, but it’s also sold under the brand name Tapazole.
Methimazole comes in tablet form and is usually taken once or twice per day, depending on your doctor’s recommendation. The dosage may start lower and be increased gradually to find what works best for you without causing side effects. It can take several weeks of treatment for methimazole to take full effect.
While on methimazole, you’ll need regular blood tests to monitor your thyroid hormone levels and make sure the dosage is correct. The medication helps prevent complications from hyperthyroidism like rapid heart rate, anxiety and weight loss. Most people stay on methimazole long-term, for months or years, but some may eventually have thyroid surgery or radioactive iodine therapy.
Possible side effects of methimazole include nausea, vomiting, indigestion, dizziness and headaches. Rare but more serious side effects can include joint pain, depression, and decreased white blood cell count. See your doctor right away if you experience any serious or persistent side effects.
Methimazole should not be used during pregnancy, as it may harm the baby. Tell your doctor if you are pregnant, breastfeeding or planning to become pregnant before starting this medication. With proper treatment and monitoring, methimazole can help get your thyroid hormone levels back to normal and relieve symptoms of hyperthyroidism.
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Using Methimazole to Treat Feline Hyperthyroidism
If your feline friend has been diagnosed with an overactive thyroid, methimazole can help get it under control. This medication works by decreasing the production of thyroid hormones to slow your cat’s metabolism back to a normal level.
You’ll need to give your cat methimazole pills twice a day, about 12 hours apart. The typical starting dose is 2.5 to 5 mg per dose, but your vet may adjust it based on follow-up blood tests. It can take several weeks of treatment to get the dosage right, so patience and regular vet checkups are key.
Some possible side effects to watch for include:
- Vomiting or diarrhea: Usually mild but let your vet know if it’s severe or persists.
- Lethargy: Some cats may become less active or sleepy. This is often temporary but call your vet if your cat seems very depressed or weak.
- Poor appetite: If your cat’s appetite decreases significantly or they stop eating entirely, contact your vet right away.
- Skin problems: Rarely, some cats develop itching, redness or other skin issues. See your vet if you notice any unusual skin changes in your cat.
The good news is most cats tolerate methimazole well and side effects tend to be minimal. However, to be safe, your vet will want to recheck your cat’s thyroid hormone levels with blood tests about a month after starting treatment and periodically thereafter to make sure the medication is working properly and the dosage is correct. With the right dosage and monitoring, methimazole can successfully help control your cat’s hyperthyroidism and allow them to live comfortably for many years.
Side Effects of Methimazole for Cats
There are some common and less common side effects of methimazole that you should be aware of. These effects usually happen in the first three months of using methimazole. The most common side effects are throwing up, losing your hunger (anorexia), and being too tired to do anything.
About 10% of cats will have problems with their stomachs. For some cats, this might be because the pill form tastes bitter. Hiding it in food or a treat might help.
Other, more dangerous side effects don’t happen as often, which is good news. About 4% of cats have problems with their blood that cause problems with clotting or platelets, bleeding, or low cell counts.
Itching on the face that is very bad, called pruritis, can happen to 2% to 3% of cats. It usually starts to show up faster, in the first three weeks of treatment.
Liver disease and an immune-mediated disorder are two other rare but dangerous effects that can happen. Each happens in less than 2% of cases.
For cats over the age of 10 who already have other diseases that can make treatment more difficult, hyperthyroidism is more noticeable. Kidney sickness is the most common one. When someone has hyperthyroidism, their kidneys filter a lot more fluid, which can hide kidney problems that are already there.
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