Clinical Information
Apply as directed by your veterinarian. If you forget a dose, apply it when you remember unless it is almost time for the next dose. Do not apply two doses at once. Your veterinarian will decide how long your cat should stay on this medication.
Methimazole blocks an enzyme in the thyroid gland called thyroid peroxidase. This enzyme is needed to make thyroid hormones (T3 and T4). By reducing hormone production, the drug lowers your cat’s thyroid levels. Most cats start to feel better within 1–3 weeks, but full hormone control can take 4–6 weeks. Each dose works for about 12–24 hours, so regular scheduling is important.
Do not use if your cat is pregnant or nursing (may harm kittens). Do not use if your cat has severe liver disease, a low white-blood-cell count, or is allergic to methimazole. Avoid use in kittens under 6 months unless the veterinarian decides benefits outweigh risks.
Tell the veterinarian about all medicines and supplements your cat takes. Methimazole can increase effects of blood thinners (e.g., heparin), change doses needed for heart medicines like beta-blockers (atenolol), and interact with certain antibiotics (trimethoprim-sulfa). Topical flea collars or other ear medications may irritate the skin and should be spaced apart. Limit fish-oil supplements unless the vet approves, as they may affect thyroid levels.
Very common (more than 1 in 10 cats): mild ear redness or greasy residue at application site. Common (1–10 in 100 cats): vomiting, decreased appetite, mild lethargy; these often improve in the first month. Uncommon (1–10 in 1000 cats): facial itching, yellowing of eyes or gums (signs of liver problems), low platelets, or white-blood-cell decline. Rare but serious: severe skin reaction, bleeding, or collapse. Contact your veterinarian right away if you notice yellow skin, bleeding, severe itching, or behavior changes.
Store at room temperature (68–77 °F, 20–25 °C) in the original syringe with the cap on. Keep away from heat, moisture, and direct sunlight. Do not freeze. Wear gloves when handling to prevent human exposure. Keep out of reach of children and other pets. Discard unused gel 90 days after the dispensing date or as directed by the pharmacy. Return expired gel to a veterinary clinic or take-back program; do not flush or pour down the drain.
Frequently Asked Questions
Q:How do I apply the gel to my cat’s ear?
A:Place a disposable glove on your hand, press the measured dose onto the inner surface of the ear flap, and gently rub for a few seconds. Switch ears with each dose to give the skin a rest. Wash your hands after removing the glove.
Q:When will I see my cat acting better?
A:Most cats have lower thyroid levels and improved energy, appetite, and weight within 1–3 weeks. Your veterinarian will recheck blood work in about a month to be sure the dose is right.
Q:What if some gel gets on my skin?
A:Wash the area with soap and water right away. Methimazole can absorb through human skin and may affect your thyroid if exposure is repeated.
Q:Can my cat still wear a flea collar or ear cleaner?
A:Yes, but apply flea treatments or ear cleaners at least 2 hours before or after the methimazole dose to reduce skin irritation and keep the medication from rubbing off.
Q:What signs mean I should call the vet immediately?
A:Call if your cat stops eating, vomits more than twice in a day, acts overly tired, scratches its face a lot, or you notice yellow eyes or gums. These can be signs of a serious reaction.
Q:How should I store and dispose of the syringe?
A:Keep the capped syringe at room temperature, away from sunlight and moisture. Do not store it in the bathroom. When empty or expired, return it to your vet or a take-back site; do not throw it in household trash.
