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Drug Details

  • Drug Name: Methimazole
  • Common Name: Tapazole®
  • Drug Type: Anti-thyroid agent
  • Used For: Treatment of Hyperthyroidism
  • Species: Cats
  • Administered: 5 mg and 10 mg tablets, Oral liquid
  • How Dispensed: Prescription only
  • FDA Approved: No

General Description


Hyperthyroidism is a common disorder of the endocrine system found mostly in middle aged to older cats. It occurs when there is an excess amount of thyroid hormones produced thus causing an increase in metabolic rate.


Methimazole in a drug that is given for life to help control your pet’s hyperthyroidism.


How It Works


Methimazole prevents the production of the thyroid hormones T3 and T4 that occur in excess in hyperthyriod cats.


Storage Information


Refrigerate oral liquid. Keep tablets in a tightly sealed container at room temperature.


Missed 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.


Side Effects and Drug Reactions


Methimazole may result in these side effects:

  • Vomiting
  • Loss of appetite
  • Liver damage


Methimazole may react with these drugs:

  • Anticoagulants
  • Radioiodine therapy


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