Cat · Felis catus · typical adult weight 2.50–7.00 kg
Methimazole is dosed at 1.25–2.5 mg per cat (NOT mg/kg) PO q12h; max 20 mg/day, max 10 mg per dose in cats, per Plumb's Veterinary Drug Handbook, 10th ed (2023, held copy; the original seed cited the 9th, which was never consulted) — Plumb's 10th ed (held) printed p.849, Methimazole monograph spanning p.849-851; page located 2026-08-05 from the book's own running heads, verified to name the drug in its body text. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207. Methimazole is used in cats for Hyperthyroidism (dose titration phase), Hyperthyroidism, Hyperthyroidism (alternative to oral), Hyperthyroidism in cats intolerant of oral medication. Routes documented in cats: PO, TRANSDERMAL. A typical adult cat weighs 2.50–7.00 kg. ExoticRx lists 5 cited dose rules for Methimazole in cats, drawn from published veterinary references. Verify against current literature before clinical use.
US trade names: Tapazole, Felimazole
| Route | Dose | Frequency | Duration | Indication | Evidence | Source |
|---|---|---|---|---|---|---|
| PO | 1.25–2.5 mg per cat (NOT mg/kg) | q12h; max 20 mg/day, max 10 mg per dose | Starting dose; recheck T4 at 2-3 weeks | Hyperthyroidism (dose titration phase) | Strong | Plumb's Veterinary Drug Handbook, 10th ed (2023, held copy; the original seed cited the 9th, which was never consulted) — Plumb's 10th ed (held) printed p.849, Methimazole monograph spanning p.849-851; page located 2026-08-05 from the book's own running heads, verified to name the drug in its body text. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207 |
| PO | 2.5 mg/cat (per animal - NOT mg/kg) | PO q12h; titrate 2.5 mg steps; max 20 mg/day | 2-4 weeks before surgery | Hyperthyroidism | Strong | Plumb's Veterinary Drug Handbook, 10th ed (2023, held copy; the original seed cited the 9th, which was never consulted) — corpus p.878 (plumb), located 2026-08-05 by exact figure+drug match (closest match at 27 chars with species on page). — LOCATOR CONVENTION 2026-08-07: the bare 'p.878' in this citation is the PDF index of the held scan, not the printed page. The PRINTED page is p.851; verified by finding the drug named there. If you are holding the book, turn to p.851. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207 — Plumb's Veterinary Drug Handbook, 10th ed (held), Methimazole monograph, printed p.851 (corpus PDF p.878), CATS: "Hyperthyroidism (label dosage; FDA-approved): Starting dose is 2.5 mg/cat (NOT mg/kg) PO every 12 […]" [INDICATION CORRECTED 2026-08-12, two readers — no page in the cited book pairs methimazole with thyroidectomy.] |
| PO | 2.5 mg/cat (NOT mg/kg) | q12h; titrate by 2.5 mg, max 20 mg/day | Chronic/lifelong (unless radioiodine or surgery) | Hyperthyroidism | Strong | Plumb's Veterinary Drug Handbook, 10th ed (2023, held copy; the original seed cited the 9th, which was never consulted) — corpus p.878 (plumb), located 2026-08-05 by exact figure+drug match (closest match at 27 chars with species on page). — located 2026-08-05 in Plumb's 10th ed, Methimazole monograph, printed p.849-851; the earlier note claiming no held source contained this figure was wrong and has been removed. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207 |
| TRANSDERMAL | 2.5 mg/cat | q12h to inner pinna, alternate ears | Chronic | Hyperthyroidism (alternative to oral) | Strong | Plumb's Veterinary Drug Handbook, 10th ed (2023, held copy; the original seed cited the 9th, which was never consulted) — corpus p.878 (plumb), located 2026-08-05 by exact figure+drug match (closest match at 27 chars with species on page). — LOCATOR CONVENTION 2026-08-07: the bare 'p.878' in this citation is the PDF index of the held scan, not the printed page. The PRINTED page is p.851; verified by finding the drug named there. If you are holding the book, turn to p.851. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207 |
| TRANSDERMAL | 2.5–5 mg per animal | q12h | Chronic | Hyperthyroidism in cats intolerant of oral medication | Strong | Plumb's Veterinary Drug Handbook, 10th ed (2023, held copy; the original seed cited the 9th, which was never consulted) — Plumb's 10th ed (held) printed p.849, Methimazole monograph spanning p.849-851; page located 2026-08-05 from the book's own running heads, verified to name the drug in its body text. — located 2026-08-05 in Plumb's 10th ed, Methimazole monograph, printed p.849-851; the earlier note claiming no held source contained this figure was wrong and has been removed. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207 |
Every held source for this drug and species, as printed. Where they differ, both are shown — the choice is yours, not ours.
| Dose (mg/animal) | Route | Source | As printed |
|---|---|---|---|
| 2.5 | PO | Papich Saunders Handbook of Veterinary Drugs, 4th edp.536 | • 2.5 mg/cat q12h PO for 7-14 days, then adjust dose to 5-10 mg/cat PO q12h as |
| 5–10 | PO | Papich Saunders Handbook of Veterinary Drugs, 4th edp.536 | • 2.5 mg/cat q12h PO for 7-14 days, then adjust dose to 5-10 mg/cat PO q12h as |
Figures are transcribed from the cited page or table of each held edition and are shown for reference only. They are not dose recommendations, they do not feed the calculator, and none has been reviewed by a veterinarian.
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These ranges are per kg. Enter your cat's weight to get the precise dose and draw-up volume — unit and concentration math done for you.
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-specific contraindications and adverse-reaction reports for cats may differ from canine / feline reference data — consult the primary citations listed with each rule.
Methimazole dose ranges in cats, with cited source references: PO 1.25–2.5 mg per cat (NOT mg/kg) q12h; max 20 mg/day, max 10 mg per dose; PO 2.5 mg/cat (per animal - NOT mg/kg) PO q12h; titrate 2.5 mg steps; max 20 mg/day; PO 2.5 mg/cat (NOT mg/kg) q12h; titrate by 2.5 mg, max 20 mg/day; TRANSDERMAL 2.5 mg/cat q12h to inner pinna, alternate ears. Reference ranges from cited sources — verify against current literature before clinical use.
Documented routes for Methimazole in cats: PO, TRANSDERMAL.
Cited course lengths for Methimazole in cats include: Starting dose; recheck T4 at 2-3 weeks; 2-4 weeks before surgery; Chronic/lifelong (unless radioiodine or surgery); Chronic. Duration depends on the indication — match it to the specific dose rule in the table above.
Methimazole is indicated in cats for: Hyperthyroidism (dose titration phase), Hyperthyroidism, Hyperthyroidism (alternative to oral), Hyperthyroidism in cats intolerant of oral medication.
These are general warnings for Methimazole across species; consult the cat dosing table above for species-specific guidance. 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.
Why a species-specific page? Methimazole pharmacokinetics differ across species: dose ranges, intervals, and route preferences are not interchangeable. Cross-extrapolation from canine doses is unsafe in cats — the rules above are the citations specific to this species, not generic recommendations.
Sourced from published veterinary references; awaiting credentialed clinical reviewer. See our editorial process. Reference only — not veterinary advice.