Methimazole

(meth-im-a-zole)

Other names for this medication: Felanorm, Felimazole, Tapazole

Used to treat high thyroid levels (hyperthyroidism).

•Usually given by mouth as a tablet or solution. A topical gel may be compounded for animals that do not tolerate oral tablets or solutions.

•It may take several weeks to see improvement in your animal’s signs.

•Your animal will need bloodwork done while receiving this medication. Do not miss these important visits.

•Common side effects include vomiting, diarrhea, decreased appetite, or lack of energy.

•Wear gloves or avoid handling if you are pregnant, nursing, or trying to become pregnant.

•Wear gloves when handling waste from treated animals, when handling broken or moistened tablets, when administering the oral solution or a topical gel, or if you have low thyroid levels.

•Wash your hands after handling this medication.

Description

•Antithyroid agent

•Available as tablets, sugar-coated tablets, and an oral solution

•Gel formulations can be specially compounded to be applied to and absorbed through the skin (transdermal).

Uses

FDA-approved uses in animals:

•Treatment of high thyroid levels (hyperthyroidism) in cats

At the discretion of your veterinarian, this medication may be used in different species or for other reasons (extra-label use).

Before this medication is given

No medication is 100% safe in all patients. Discuss with your veterinarian:

•Any other medications or supplements your animal is taking

•Any conditions or diseases your animal currently has or has had in the past

•Any side effects your animal has had to medications in the past

•The risks of using this medication if your animal is pregnant or nursing

Warnings for animals

Do not use in animals:

•That are allergic to this medication

•That are allergic to carbimazole or polyethylene glycol

•With an autoimmune disease

•With blood disorders, such as anemia, low platelet levels, or clotting disorders

•With kidney failure

•That are pregnant or nursing

Use with caution in animals:

•With liver or kidney disease

Certain medications are not allowed in some animal competitions. Check rules and regulations when your animal is taking a medication.

Warnings for humans

•Wear gloves when handling:

‐Waste from treated animals, including litter, feces, urine, and vomit.

‐Broken or moistened tablets.

‐The oral solution or transdermal gels.

‐If you have low thyroid levels.

•Wear gloves or avoid handling if you are pregnant, nursing, or trying to become pregnant.

•Wash your hands with soap and water after handling.

•The oral solution can cause skin and eye irritation. In case of accidental skin contact, wash the area immediately. In case of accidental eye exposure, rinse eyes immediately with water and contact a physician if irritation occurs.

How do I give this medication?

•Give with or without food.

•Hiding tablets in food may help mask the bitter taste of this medication.

•Do not split or crush sugar-coated tablets.

•Measure liquids using only the provided dosing syringe.

•When using a transdermal gel:

‐Apply the dose to the inside of the ear flap (pinna).

‐Remove any leftover crusted medication before applying the next dose.

‐Alternate ears with each application.

‐Do not use if the gel appears separated.

Give exactly as your veterinarian has prescribed. Always follow the instructions on the prescription label.

Side effects

Common – contact your veterinarian if any of these signs are severe, continue to occur, or worsen over time:

•Vomiting, diarrhea, or decreased appetite

•Increased vocalization

•Lack of energy

Severe – stop the medication and contact your veterinarian immediately if you notice any of these signs:

•Complete loss of appetite

•Bruising or other signs of bleeding

•Severe lack of energy or weakness

•Yellowing of the skin, gums, or whites of the eyes (jaundice)

•Bleeding from excessive itching and scratching, usually on the face

How will I know it's working?

•This medication needs to be given consistently for several weeks before it will reach full effect. You should see a gradual improvement in your animal’s signs as the medication becomes fully effective.

‐However, side effects can occur right away.

•Your veterinarian will need to run follow-up tests to determine how well your animal is tolerating this medication and evaluate how well it is working.

Contact your veterinary clinic if your animal’s signs worsen or do not improve.

How long will the medication effects last?

•This medication will stop working within 24 hours of the last dose.

How long do I give it for?

This medication can be given for different lengths of time. It is often a lifelong medication but is sometimes used as a temporary treatment until surgical removal or radiation of the thyroid gland. Give it for as long as your veterinarian tells you. Make sure to refill the prescription to avoid interruptions in treatment.

Overdose

If you witness or suspect an overdose, call your veterinarian or an animal-specific poison control center (consultation fee applies):

•ASPCA Animal Poison Control Center: (888) 426-4435

•Pet Poison Helpline: (855) 764-7661

Have the product or label with you if possible.

Missed dose

In most cases, if you miss a dose:

•Give it when you remember, then return to the regular dosing schedule. If it is close to the time for the next dose:

•Skip the missed dose.

•Give the next dose at the next scheduled time.

•Continue the regular dosing schedule.

If you are unsure, call your veterinary clinic. Do not double-up or give extra doses.

Storage

•Store in the original container at room temperature.

•Protect from light.

•Keep out of reach of children and animals.

Disposal

Do not flush this medication down the toilet or wash it down the sink. Options for disposing of unused or expired medications include:

•Drug take-back sites: This is preferred whenever possible. To find a site near you, contact your local law enforcement or waste management authorities.

•Home disposal: Throw away in the regular trash.

Do not save leftover medication or give it to others to use.