ExoticRx · exoticrx.com/drugs/methimazole
US brand names:Tapazole, Felimazole
Methimazole is dosed at 1.4 mg/kg PO q24h in rabbits, per DiGeronimo PM, Brandao J. Update on thyroid disease in rabbits and guinea pigs. In: Wyre NR, Chen S, eds. Vet Clin North Am Exot Anim Pract: New and Emerging Diseases: an Update; 2020;23:373-381. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.879 — Carpenter's Exotic Animal Formulary 6th ed, Table 10.10 (Miscellaneous Agents Used in Rabbits). Verify against current literature before clinical use.
Inhibits thyroid peroxidase, blocking iodine organification and thyroid hormone synthesis. Does not destroy thyroid tissue.
Cats: monitor renal function (treating hyperthyroidism may unmask underlying renal disease). Side effects include anorexia, vomiting, facial pruritus, and blood dyscrasias. Monitor CBC and liver enzymes.
Species references:All Cat (Domestic) drugsAll Guinea Pig drugsAll Rabbit (Domestic) drugs
Each ExoticRx dose rule is graded by the strength of its primary evidence — see the editorial process.
A dog/cat sample is shown here. Cited dosing for all 3 species — reptiles, birds, pocket pets, livestock, and equine — is free on the per-species pages above. Pro adds the weight-based calculator for every species.
| Species | Route | Dose | Frequency | Evidence | Source |
|---|---|---|---|---|---|
| Cat (Domestic) | PO | 2.5 mg/cat (per animal - NOT mg/kg) | PO q12h; titrate 2.5 mg steps; max 20 mg/day | Strong | Plumb's Veterinary Drug Handbook, 10th ed (2023) — printed p.851. — Plumb's Veterinary Drug Handbook, 10th ed, Methimazole monograph, printed p.851, CATS: "Hyperthyroidism (label dosage; FDA-approved): Starting dose is 2.5 mg/cat (NOT mg/kg) PO every 12 […]"Compilation only — we have not located an independent source that prints this figure. |
| Cat (Domestic) | TRANSDERMAL | 2.5–5 mg per animal | q12h | Strong | Plumb's Veterinary Drug Handbook, 10th ed (2023) — Plumb's 10th ed printed p.849, Methimazole monograph spanning p.849-851. — Plumb's 10th ed, Methimazole monograph, printed p.849-851.Compilation only — we have not located an independent source that prints this figure. |
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View PlansSource citations and evidence levels available on the live page. Reference only — verify against current literature before clinical use.