OtherPrescription RequiredCat
Methimazole (Felimazole)
Methimazole
Drug Class
Other
Available Forms
Oral tablet, Transdermal gel
Approved For
Cat
Dosage Guide
Cats: 2.5-5 mg/cat PO twice daily. Transdermal gel: applied to inner ear pinna. Dose titrated based on T4 levels. Monitor T4, CBC, and renal function every 3-6 months.
This is a general reference only. Always follow your veterinarian's prescribed dosage for your specific pet.
Side Effects
- •Vomiting and anorexia (up to 20% of cats initially)
- •Lethargy and depression
- •Facial excoriation/pruritus (serious — discontinue if occurs)
- •Hepatopathy (elevated liver enzymes)
- •Blood dyscrasias (thrombocytopenia, leukopenia — rare but serious)
Important Warnings
- !Side effects occur in ~20% of cats — many are transient
- !Facial pruritus/excoriation requires immediate discontinuation
- !Regular blood monitoring is essential
- !Transdermal gel — wear gloves when applying
- !Does NOT cure hyperthyroidism — the tumor continues to grow
Contraindications
Do not use this medication in the following situations:
- ✕Known hypersensitivity to methimazole
- ✕Pre-existing significant liver disease
- ✕Pregnancy (teratogenic)
Medical Disclaimer
This medication guide is for informational purposes only. Always consult a licensed veterinarian before administering any medication to your pet. Dosages vary based on weight, age, health status, and concurrent medications. Never give human medications to pets without veterinary approval — many common human drugs are toxic or fatal to animals.