Methimazole

Side effects occur in less than 5% of all cases, but can be serious, such as a decreased white blood cell count (agranulocytosis); contact a veterinarian immediately if your pet display signs of a sore throat. Excessive bleeding can also occur as a result of a decrease in blood platelets. Very rarely, liver failure and its ensuing complications have been associated with Methimazole.

More common side effects are skin-related, including rash, itching, hives, abnormal hair loss, and skin pigmentation. Other side effects may include swelling, nausea, vomiting, heartburn, loss of taste, joint or muscle aches, drowsiness, dizziness, numbness, and headache. Do not use in pregnant or nursing animals.

Methimazole must be used only in cats. It should never be used on animals, which are prone to allergy to the drug. Extreme care should be taken while using this medication in animals with a known history of liver impairment, immune-system disease or blood disorders. Regular blood tests to monitor toxicity on blood cells and liver are suggested in cats, which are on methimazole for a long period.The medication should be administered life long as the symptoms might reappear once the medication is stopped. It is advisable to use methimazole for the short term management of the disease as it involves side effects. Surgical removal of the thyroid gland or radiation treatment would be more appropriate for a lasting solution. Pregnant and nursing cats should not be given this drug. Drug overdose might result in blood disorders or liver toxicity. 

Do not take with theophylline (Theo-Dur), warfarin (Coumadin), digoxin (Lanoxin), a beta blocker such as atenolol (Tenormin), metoprolol (Lopressor), or propranolol (Inderal). Talk to your vet before starting any serious treatment plan.

Methimazole is an anti-thyroid tablet used in the treatment of hyperthyroidism in cats, which, might result in weight loss, abnormal appetite and heart problems. When administered, methimazole restores the thyroid hormone levels back to normal by interfering with iodine, which has a major role in thyroid function. 

Methimazole comes as 5 mg and 10 mg tablets. The recommended primary dose of methimazole is 5 mg per cat, three times daily and the dosage should be increased, if no improvement is noticed in the situation. Once the condition stabilizes, the dose could be reduced after taking the opinion of the veterinarian. Ensure that the full course is completed to prevent relapse or the chances of developing resistance to the drug. 

Ask your veterinarian or consult with one of our pet care specialists at 1-800-844-1427.

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian. Always seek the advice of your veterinarian or other qualified professional with any questions you may have regarding a medical condition. Never disregard or delay seeking professional advice due to what you may have read on our website. Our medications are FDA approved and/or EPA regulated when and as required by law.