What is carbimazole?
Carbimazole is a medication used to treat an overactive thyroid (hyperthyroidism) in cats and other animals. Carbimazole lowers thyroid hormone levels.
It is used off label (extra label) in veterinary medicine in Canada and the United States. Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada.
In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.
How do I give my pet carbimazole?
- Carbimazole comes in tablet form.
- Tablets are given orally (by mouth).
- This medication may be given with or without food.
- If your animal vomits or acts sick after receiving the drug on an empty stomach, try giving the next dose with food or a small treat. If vomiting continues, contact your veterinarian.
- Give this medication to your pet for the entire time prescribed by your veterinarian, even if it appears that your pet is feeling better.
This medication should start to take effect within a few days, although effects may not be noticeable right away.
What if I miss giving my pet the medication?
If you miss a dose, give it as soon as you remember, and then wait the recommended time for the next dose, as prescribed by your veterinarian. Do not give the pet two doses at once or give extra doses.
Are there any potential side effects?
Carbimazole may cause the following side effects:
- Lack of appetite and/or energy
- Vomiting
Serious adverse reactions may occur. If any of the following signs develop, stop giving carbimazole and contact your veterinarian immediately:
- An allergic reaction such as irregular breathing, rash, fever, puffiness and swelling around the face
- Fever
- Severe lack of energy
- Weakness; unable to get up or stand
- Severe itching or scratching, especially of the face or head
Drug sensitivities can develop over time, with repeated exposure. Your pet may have no reaction after the first few doses but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment.
Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This short-acting medication should stop working within 24 hours, although effects may last longer in pets with kidney or liver disease.
Are there any risk factors for this medication?
DO NOT USE carbimazole in:
- Pets that are allergic to any component of the medication or allergic to methimazole or polyethylene glycol (PEG)
- Pets that are pregnant or nursing
- Pets with liver disease
- Pets with diabetes mellitus
- Pets with autoimmune problems
- Pets with blood cell problems
USE WITH CAUTION in:
- Pets with decreased liver or kidney function
Are there any drug interactions I should be aware of?
Certain medications should be USED WITH CAUTION when given with carbimazole, including:
- Anticoagulants (e.g., heparin, warfarin)
- Benzimidazole antiparasitics (e.g., fenbendazole)
- Beta-blockers (e.g., atenolol, propranolol)
- Chloramphenicol
- Digoxin
- Iodine 131
- Phenobarbital
- Prednisolone/prednisone
- Theophylline
Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.
Is any monitoring needed with this medication?
- Your veterinarian will assess baseline blood work (including thyroid function), blood pressure, and body weight before starting this medication.
- Your veterinarian will continue monitoring blood work throughout treatment.
- Your veterinarian will schedule follow-up visits for monitoring. In this case, follow your veterinarian’s directions.
- At home, monitor for any side effects such as those noted above. If any occur, stop using the medication and contact your veterinarian.
How do I store carbimazole?
- Store at room temperature, less than 77°F (25°C).
- Store in a tight container, protected from light.
- Keep medication out of reach of children and pets.
What should I do in case of emergency?
If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet’s weight and symptoms. Adverse effects should be reported to the FDA or Health Canada.
