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Carbimazole

Prescription

Antithyroid agent (thionamide)

Last reviewed 21 Apr 2026 · PetCare.AI Editorial Team

Species

Cat, Dog

Brands

4 available

Interactions

1 documented

Formulations

Mechanism of action

Prodrug rapidly converted to methimazole; inhibits thyroid peroxidase enzyme, blocking iodine organification and coupling of iodotyrosines, thereby reducing thyroid hormone (T3 and T4) synthesis

At a glance

Class

Antithyroid agent (thionamide)

Schedule

Prescription

Storage

Below 25°C, protect from moisture

Dosing

🐈

Cat

Feline hyperthyroidism

Dose

10–15 mg/cat

Route

Frequency

SID to BID (start BID, consolidate to SID once euthyroid)

Max dose

15 mg/dose; 30 mg/day

Duration: Long-term / lifelong if radioiodine or surgery not pursued

🐕

Dog

Hyperthyroidism (rare; thyroid carcinoma)

Dose

5–15 mg/dog

Route

Frequency

BID to TID

Max dose

20 mg/dose; 60 mg/day

Duration: Pre-surgical stabilization or long-term

Educational reference only

This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet. Find a vet near you →

Formulations

💊

Tablet — 1

Strength

5mg

Available in India

💊

Sustained-release tablet — 2

Strength

10mg

Strength

15mg

Storage

Below 25°C, protect from moisture

Safety

Absolute contraindications — do not use

Known hypersensitivity to carbimazole or methimazole

Use with caution

Pre-existing liver disease
Hepatotoxicity risk
Concurrent azole antifungals
May alter thyroid function testing

Adverse effects

Common

Vomiting

Anorexia

Facial excoriation (cats)

Lethargy

Serious

Agranulocytosis

Hepatotoxicity

Thrombocytopenia

Immune-mediated hemolytic anemia

Monitoring parameters

Total T4 at 2–3 weeks post-initiationCBCHepatic enzymesBUN/Creatinine (unmasking of renal disease)Body weight

Educational reference only

Interactions

Contraindicated — 1

Methimazole

contraindicated

Carbimazole is a prodrug converted to methimazole. Combining them is effectively double-dosing the same drug, causing severe hypothyroidism and myelosuppression.

Management: NEVER combine. Use one or the other. When switching, discontinue first agent before starting the second.

Educational reference only

Brands

International

Vidalta

Intervet/MSD Animal Health

Neo-Mercazole

Nicholas Piramal

India

Neo-Mercazole

Abbott India

Thyrozole

Sun Pharma

FAQs

Frequently asked questions

›What is Carbimazole?

Carbimazole is a antithyroid agent (thionamide) used in pets. Prodrug rapidly converted to methimazole; inhibits thyroid peroxidase enzyme, blocking iodine organification and coupling of iodotyrosines, thereby reducing thyroid hormone (T3 and T4) synthesis

›What is Carbimazole used for in pets?

Carbimazole is used in veterinary medicine for: Feline hyperthyroidism; Hyperthyroidism (rare; thyroid carcinoma).

›What is the Carbimazole dose for cats?

For cats, Carbimazole is typically dosed as follows — Feline hyperthyroidism: 10–15 mg/cat PO SID to BID (start BID, consolidate to SID once euthyroid). Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.

›What is the Carbimazole dose for dogs?

For dogs, Carbimazole is typically dosed as follows — Hyperthyroidism (rare; thyroid carcinoma): 5–15 mg/dog PO BID to TID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.

›What are the side effects of Carbimazole?

Common: Vomiting, Anorexia, Facial excoriation (cats), Lethargy. Serious (call your vet immediately): Agranulocytosis, Hepatotoxicity, Thrombocytopenia, Immune-mediated hemolytic anemia.

›Does Carbimazole need a prescription?

Yes. Carbimazole is a prescription medication and should only be administered under veterinary supervision.

›When should Carbimazole not be used?

Do not use Carbimazole if: Known hypersensitivity to carbimazole or methimazole.

Educational reference only

References

The PetCare.AI drug reference is built from 13 authoritative sources cited across 580 drug monographs.

Textbooks & handbooks — 5

Plumb's Veterinary Drug Handbook
Withrow & MacEwen's Small Animal Clinical Oncology
Merck Veterinary Manual
NRC Nutrient Requirements of Dogs and Cats
Veterinary Pharmacology and Therapeutics (Riviere & Papich)

Clinical guidelines & consensus — 4

ASPCA Animal Poison Control Center Guidelines
AAHA Diabetes Management Guidelines
ASPCA Poison Control Guidelines
RECOVER CPR Guidelines

Journals & peer-reviewed studies — 2

EPIC Study (J Vet Intern Med 2016)
JVIM FAT CAT Study

Regulatory & approvals — 1

CDSCO Veterinary Drug Approval Registry (1969–2026)

Databases — 1

Washington State University VCPL MDR1 Database