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Roxee Medication Guide

Methimazole

Medication reference facts with explicit FDA-approval, off-label, source-limited, and safety context. Roxee does not sell, prescribe, or dispense medications.

Cat Reference complete FDA data linked Rx required Coated Tablets Multiple FDA labelers Official label facts Owner quick guide first
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Data freshness

Reference facts
Reference refreshed
Jun 22, 2026, 10:41 a.m.

These are the reference facts Roxee uses on browse cards and quick facts.

FDA applications
FDA application data refreshed
Jun 22, 2026, 10:41 a.m.

Sponsor, product, and application records imported from Animal Drugs @ FDA.

Safety reports
Safety data refreshed
Jun 13, 2026, 11:29 a.m.

openFDA reaction terms and case summaries are supporting evidence, not proof of causality.

Source timing details
Source timing details
  • Reference facts: Source Roxee | Refreshed Jun 22, 2026, 10:41 AM UTC
    The reference fact projection used for browse cards and quick facts.
  • Animal Drugs @ FDA: Source FDA | Refreshed Jun 22, 2026, 10:40 AM UTC
    Applications/products are imported from FDA export data.
  • Animal Drugs @ FDA previews: Source FDA | Refreshed Feb 9, 2026, 3:05 AM UTC
    Label highlights/doc links are fetched from FDA preview endpoints.
  • Animal Drug Product Listing Directory (NDC): Source FDA | Refreshed Jun 22, 2026, 10:41 AM UTC
    Package/product NDCs from FDA’s electronic listing directory (XLS).
  • openFDA reaction terms: Source FDA openFDA | Refreshed Jun 22, 2026, 10:45 AM UTC
  • openFDA case summaries: Source FDA openFDA | Refreshed Jun 22, 2026, 10:45 AM UTC
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Methimazole

Methimazole

Drug type: Generic ingredient • Branded profile • FDA branded products available

Cat Coated Tablets Rx required 100% reference complete

Species: Cat

Manufacturer: Multiple FDA labelers

Medication Snapshot

Merged from the current Roxee medication system with field-level provenance, freshness, and completeness tracking.

Methimazole

Used to manage hyperthyroidism in cats. Species commonly shown: Cat.

Generic name
Methimazole
Brand names
Felimazole®, Felanorm®, Methimazole Coated Tablets, Felanorm
Manufacturer
Multiple FDA labelers
Species
Cat
Dosage forms
Coated Tablets, Oral Solution
Prescription
Prescription required
Completeness
100%
Validation
Complete
Brand names
Felimazole® Felanorm® Methimazole Coated Tablets Felanorm Felimazole Methimazole ReguZol
Dosage forms
Coated Tablets Oral Solution

Indications / Uses

Used to manage hyperthyroidism in cats.

Administration / How To Give

Oral

Storage

Store at room temperature.

Warnings / Contraindications

Use caution with liver disease, blood disorders, or autoimmune conditions.

  • Use caution with liver disease, blood disorders, or autoimmune conditions.

Side Effects

Vomiting, decreased appetite, lethargy, facial itching. Rare: low blood cell counts.

FAQ

Cat

Yes. Roxee shows this as prescription-only.

Coated Tablets, Oral Solution

Store at room temperature.

Related Medications

Famotidine Same category: GI Maropitant Citrate Same category: GI Omeprazole Same category: GI Praziquantel Same category: GI Trilostane Same category: GI Levetiracetam Same category: Endocrine / Hormone

Related Conditions

Anemia (regenerative/non-regenerative) Hyperthyroidism Hyperthyroidism Pruritus (itching, undifferentiated) Thrombocytopenia (ITP) Weight loss

Source Transparency

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Pet Owner Quick Guide

Start here first for the safest next-step summary before the deeper medication detail.

Used for:

For the treatment of hyperthyroidism in cats.

Dosing note:

Exact dosing depends on your pet's species, weight, and health status. Use your veterinarian's instructions for the exact dose and schedule.

What to watch for:

  • Use caution with liver disease, blood disorders, or autoimmune conditions
  • Loss of appetite (1 reports)
  • Haematuria (1 reports)
  • General illness (1 reports)

When to call the vet:

  • Repeated vomiting or diarrhea.
  • Severe lethargy (hard to wake, very low energy).
  • Collapse or fainting.
  • Trouble breathing.
  • Facial swelling or hives.
  • Blood in vomit or stool.

What to tell or ask your vet today:

  • Is this medicine the right fit for my pet’s current symptoms?
  • Which warning signs mean I should call back right away?
  • How should I handle missed doses or refusal to take the medicine?

Next actions

Talk to a Vet / Find a Vet Near You Save to pet meds Share page Review report evidence
Research brief

Medication Research Insights

A source-aware map of what to know, what is uncertain, and what to verify with your veterinarian.

Source Backed Signals

What to know

Evidence-backed context Limited

Roxee has limited cited overview evidence for Methimazole; use the official documents and your veterinarian's instructions for product-specific decisions.

Source: openFDA case USA-USFDACVM-2025-US-069686
Safety signal coverage Reported signals

32 tracked reaction signals; 32 reported cases; 29 serious reports; 1 species group. These are reporting and label-derived signals for interpretation with a veterinarian.

Source: openFDA case USA-USFDACVM-2025-US-069686
Interpretation guardrail Not causation

Adverse-event reports help form a watch list, but they do not prove the medication caused the reaction and they are not a risk ranking between medications.

Evidence tension

Stronger signal Label / review

Official labels, package inserts, and reviewed summaries carry more weight than isolated reports.

Source: openFDA case USA-USFDACVM-2025-US-069686
Weaker signal Reported data

Case reports and openFDA terms are useful for pattern awareness, but they are incomplete, can include multiple exposures, and do not estimate an individual pet's probability of harm.

Reaction signal map

Most reported reactions Top terms

Loss of appetite (1 reports), Haematuria (1 reports), General illness (1 reports), Gait abnormality (1 reports), Fracture (1 reports)

Body systems represented Signal grouping

Digestive (2), Neurologic (1), Behavior (1), Other (28)

Explore supporting adverse reports

Species and breed lens

Species represented in reports Species lens

Cat (32 reports)

Breed metadata in reports Metadata only

Domestic Shorthair (5), Domestic Mediumhair (2), Siberian (1). These are report metadata, not proof that a breed is at higher risk.

What your vet may verify

Fit for this patient Vet check

Verify whether Methimazole fits the pet's species, current diagnosis, age, weight, organ status, pregnancy/lactation status, and concurrent medications.

Evidence limitations Evidence review

Separate label-backed warnings from adverse-event reports and owner observations before changing the plan.

What to watch next

Watch list Owner-safe

Use caution with liver disease, blood disorders, or autoimmune conditions, Loss of appetite, Haematuria, General illness

Call sooner if Escalation

Repeated vomiting or diarrhea. Severe lethargy (hard to wake, very low energy). Collapse or fainting.

Bottom line: Use this Methimazole brief as a structured watch list and source map, not as a reason to start, stop, or change treatment without your veterinarian.
Vet source depth
  1. openFDA case USA-USFDACVM-2025-US-069686 · adverse_reaction · adverse reactions
  2. Contraindication source · fda_animal_drugs · warnings contraindications
  3. FDA application profile · official_label · quick facts
  4. FDA application profile · official_label · quick facts
  5. Medication usage source · fda_animal_drugs · quick facts
  6. FOI · document · documents
  7. SPL · document · documents
  8. FOI · document · documents

Evidence

Review status / Updated / Sources

Review status: Clinical reviewer not listed

Updated: February 12, 2026, 7:40 PM UTC

Sources:
Safety & side effects

Side effects to monitor:

  • Use caution with liver disease, blood disorders, or autoimmune conditions
  • Loss of appetite
  • Haematuria
  • General illness

Most reported reactions:

  • Loss of appetite (1 reports)
  • Haematuria (1 reports)
  • General illness (1 reports)
Explore reported case details

Emergency warning signs:

  • Repeated vomiting or diarrhea.
  • Severe lethargy (hard to wake, very low energy).
  • Collapse or fainting.
  • Trouble breathing.
Talk to a Vet / Find a Vet Near You Start Symptom Intake

Vet Fast Scan

Source-backed clinical checkpoints for quick review.

FDA-labeled species
Cat
Indication / use
For the treatment of hyperthyroidism in cats.
Form / route / dose
Form: Coated Tablets, Oral Solution
Route: Oral
Confirm product label and patient-specific plan.
Warnings
  • High: Use caution with liver disease, blood disorders, or autoimmune conditions.
Adverse-event caveat
openFDA adverse-event cases are reported signals. They are not verified, do not prove causation, and do not estimate a pet's individual risk.
Source docs

Quick Facts

Official label facts first, then secondary summaries. Marketing content is separated below.

Species: Cat
Manufacturer: Multiple FDA labelers
Form: Coated Tablets, Oral Solution
Identifiers:
ANADA: 200771 ANADA: 200814 NADA: 141292 NDC Package: 11695-7048-1 NDC Package: 11695-7049-1 NDC Package: 17033-225-10 NDC Package: 17033-250-10 NDC Package: 51311-044-30 NDC Package: 51311-044-40 NDC Package: 55529-170-02 NDC Package: 55529-170-14 NDC Package: 86032-064-01 NDC Package: 86101-059-11 NDC Package: 86101-060-11 NDC Package: 86136-157-36 NDC Package: 86136-158-36 NDC Product: 11695 NDC Product: 17033 NDC Product: 51311 NDC Product: 55529
Source metadata:

Warnings / Contraindications

Use caution with liver disease, blood disorders, or autoimmune conditions.

  • High: Use caution with liver disease, blood disorders, or autoimmune conditions.
Source metadata:

Adverse Reactions

Snapshot first, detailed rows second. This section summarizes signal data and is not a diagnosis.

Reported case explorer

Filter stored openFDA reports by pet and report attributes. Counts describe reports in this data set, not risk.

Clear filters
openFDA adverse-event cases are reported signals. They are not verified, do not prove causation, and do not estimate a pet's individual risk.
Stored reports
9
Matching reports
1
Active filters
2
Selected filters
Reaction: Abdominal pain Clear Body system: Digestive Clear
Reset
Drill into common report signals
Vomiting (4) Behavioural disorder NOS (3) Medication error NOS (2) Abdominal pain (1) Other (8) Digestive (5) Behavior (3) Skin & allergy (2)
Showing up to 50 matching reports.

USA-USFDACVM-2025-US-069686

Received 2025-11-12 · MSK · MSK

Serious
Species
Cat
Breed
Domestic Shorthair
Size / weight
Under 10 lb (3.9 Kilogram)
Age
8+ years (14 Year)
Sex
Female Neutered
Region
USA
Reactions
Swollen limbEpistaxisDeath by euthanasiaMalaiseHeart murmurNeutropeniaThrombocytopeniaHypoalbuminaemiaIncreased drinkingHaematuriaDecreased urine concentrationElevated protein:creatinine ratioDehydrationLymphopeniaAbdominal painIntestinal disorder NOSAbnormal radiograph findingRenal failureRenal disorder NOSInflammatory bowel disorderBronchopulmonary inflammationBruisingAnaemia NOSTachycardiaPale mucous membraneElevated alanine aminotransferase (ALT)Prolonged one stage prothrombin time (OSPT)Intentional misuseMedication error NOSPolyuriaAnorexiaAzotaemiaNecropsy performedHaemorrhage NOSFractureThyroid adenomaPancreas disorder
Body systems
OtherDigestive
Outcomes
Euthanized

Tap or hover a reaction to see what it means in plain language.

Tracked signals
32
Reported cases
32
Serious reports
29
Species represented
1
Grouped by Body System
Digestive (2) · Loss of appetite, Decreased appetite Neurologic (1) · Unsteady walking (ataxia) Behavior (1) · Behavioral disorder (unspecified) Other (28) · Haematuria, Glucosuria, General illness
Most Reported Reactions
Reaction Body system Cases Species Serious cases
Digestive 1 Cat 1
Other 1 Cat 1
Other 1 Cat 1
Other 1 Cat 1
Other 1 Cat 1
Other 1 Cat 1
Other 1 Cat 1
Other 1 Cat 1

Species coverage: Cat (32)

View detailed reaction table
Reaction Body system Species Seriousness Frequency Reports
Neurologic Cat Non-serious - 1
Digestive Cat Serious - 1
Other Cat Serious - 1
Other Cat Non-serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Non-serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Digestive Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Behavior Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Source metadata:

Storage & Handling

Store at room temperature.

Source Documents

The most useful source links appear first; full previews and metadata stay in the veterinary/professional layer.

Use original documents to confirm product-specific warnings, ingredients, and handling details with your veterinarian.

Felanorm® SPL · SPL Methimazole Coated Tablets SPL · SPL Felimazole® SPL · SPL

Full source previews and metadata remain in the veterinary/professional layer.

Owner handouts

0
No owner handouts linked yet.

Official label / PI

0
No official label or package insert links yet.

SPL

11

FOI

3

Felanorm®

SPL · SPL

Open original
FDA Structured Product Label

Felanorm®

Rendered from Roxee's cached FDA SPL package contents for on-page reading. Use Open original for the raw FDA ZIP/XML source.

Sponsor
Virbac AH, Inc.
ANADA
200-771
Status
RX
Form
Oral Solution
Route
Oral
Composition / specifications
5 mg/mL

Cats

Indication

For the treatment of hyperthyroidism in cats.

Dosage

The starting dose is 2.5 mg administered every 12 hours. Following 3 weeks of treatment, the dose should be titrated to effect based on individual serum total T4 (TT4) levels and clinical response. Dose adjustments should be made in 2.5 mg increments. The maximum total dosage is 20 mg per day divided, not to exceed 10 mg as a single administration.

Methimazole Coated Tablets

SPL · SPL

Open original
FDA Structured Product Label

Methimazole Coated Tablets

Rendered from Roxee's cached FDA SPL package contents for on-page reading. Use Open original for the raw FDA ZIP/XML source.

Sponsor
Felix Pharmaceuticals Pvt. Ltd.
ANADA
200-814
Status
RX
Form
Coated Tablets
Route
Oral
Composition / specifications
2.5 mg or 5 mg methimazole per tablet

Cats

Indication

For the treatment of hyperthyroidism in cats.

Dosage

The starting dose of Methimazole Coated Tablets is 2.5 mg administered every 12 hours. Following 3 weeks of treatment, the dose should be titrated to effect based on individual serum total T4 (TT4) levels and clinical response. Dose adjustments should be made in 2.5 mg increments. The maximum total dosage is 20 mg per day divided, not to exceed 10 mg as a single administration.

Felimazole®

SPL · SPL

Open original
FDA Structured Product Label

Felimazole®

Rendered from Roxee's cached FDA SPL package contents for on-page reading. Use Open original for the raw FDA ZIP/XML source.

Sponsor
Dechra, Ltd.
NADA
141-292
Status
RX
Form
Coated Tablets
Route
Oral
Species
Cat

Cats

Indication
For the treatment of hyperthyroidism in cats.
Dosage
The starting dose is 2.5 mg administered every 12 hours. Following three weeks of treatment, the dose should be titrated to effect based on individual serum total T4 (TT4) levels and clinical response. Dose adjustments should be made in 2.5 mg increments. The maximum total dosage is 20 mg per day divided, not to exceed 10 mg as a single administration.
Limitations
Due to potentially serious adverse reactions such as hepatopathy, immune-mediated anemia, thrombocytopenia, and agranulocytosis, cats on methimazole therapy should be monitored closely for any sign of illness including anorexia, vomiting, head/facial pruritus or edema, depression/lethargy, weight loss, anemia, skin lesions, diarrhea, fever, or lymphadenopathy. If a cat becomes ill while on FELIMAZOLE Coated Tablets, the drug should be stopped and appropriate hematological and biochemical testing should be done (see ANIMAL SAFETY and POST APPROVAL EXPERIENCE).

Felanorm SPL

SPL · Structured Product Label

Open original
FDA Structured Product Label XML for Felanorm. Use the source link for the full official labeling record.

ReguZol SPL

SPL · Structured Product Label

Open original
FDA Structured Product Label XML for ReguZol. Use the source link for the full official labeling record.

Methimazole SPL

SPL · Structured Product Label

Open original
FDA Structured Product Label XML for Methimazole. Use the source link for the full official labeling record.

Felimazole SPL

SPL · Structured Product Label

Open original
FDA Structured Product Label XML for Felimazole. Use the source link for the full official labeling record.

Felanorm SPL

SPL · Structured Product Label

Open original
FDA Structured Product Label XML for Felanorm. Use the source link for the full official labeling record.

Methimazole SPL

SPL · Structured Product Label

Open original
FDA Structured Product Label XML for Methimazole. Use the source link for the full official labeling record.

Methimazole SPL

SPL · Structured Product Label

Open original
FDA Structured Product Label XML for Methimazole. Use the source link for the full official labeling record.

Felanorm SPL

SPL · Structured Product Label

Open original
FDA Structured Product Label XML for Felanorm. Use the source link for the full official labeling record.

FOI Summary oA 200-771 Approved July 8, 2024.pdf

FOI · FOI

Open original

FOI Summary oA 200-814 Approved June 27, 2025.pdf

FOI · FOI

Open original

UCM165091.pdf

FOI · FOI

Open original
Source metadata:
Veterinary reference (advanced)

Canonical medication sections are above. This legacy block remains available for deeper cross-reference without cluttering the primary workflow.

At a Glance

Quick facts and links to official labeling and safety signals.

Data freshness
  • Reference facts: Source Roxee | Refreshed Jun 22, 2026, 10:41 AM UTC
    The reference fact projection used for browse cards and quick facts.
  • Animal Drugs @ FDA: Source FDA | Refreshed Jun 22, 2026, 10:40 AM UTC
    Applications/products are imported from FDA export data.
  • Animal Drugs @ FDA previews: Source FDA | Refreshed Feb 9, 2026, 3:05 AM UTC
    Label highlights/doc links are fetched from FDA preview endpoints.
  • Animal Drug Product Listing Directory (NDC): Source FDA | Refreshed Jun 22, 2026, 10:41 AM UTC
    Package/product NDCs from FDA’s electronic listing directory (XLS).
  • openFDA reaction terms: Source FDA openFDA | Refreshed Jun 22, 2026, 10:45 AM UTC
  • openFDA case summaries: Source FDA openFDA | Refreshed Jun 22, 2026, 10:45 AM UTC
Official (FDA)
Identity: Generic ingredient • FDA branded products available
Official FDA brands: Felanorm Felimazole Methimazole ReguZol
Manufacturer mapping: Multiple FDA labelers
Case-reported brands (openFDA): MSK
Catalog species: Cat • FDA-labeled species: Cat
Rx/OTC: RX
Form/route: Coated Tablets, Oral Solution • Oral
Applications: ANADA 200-771 • ANADA 200-814 • NADA 141-292
NDC: Packages 11695-7048-1 11695-7049-1 17033-225-10 17033-250-10 51311-044-30 51311-044-40 • Products 11695 17033 51311 55529 86032 86101
Documents: 3 (FOI: 3) • SPL: 3 • Label highlights • Official documents
Safety (openFDA)
Top reactions: Dog 0 • Cat 63 • View
Case summaries: 9 (showing 8) • View
openFDA reports are unverified and do not prove causation.
Explore
Linked using: Fda_Label (0.95), Fda_Label (0.95), Fda_Label (0.95)
Diagnosis Codes
ICD10_CM: E05.90
Thyrotoxicosis, unspecified without thyrotoxic crisis or storm

Counseling and Monitoring Highlights

Global Pet owner/Vet mode is controlled in the header. This section avoids duplicate in-page persona tabs.

Owner-facing counseling points
  • Use caution with liver disease, blood disorders, or autoimmune conditions. (Contraindication, High)
Top reaction signals
Loss of appetite (1) Haematuria (1) General illness (1) Gait abnormality (1) Fracture (1) Fever (1) Eye disorder NOS (1) Epistaxis (1)

Identifiers & Packages

Normalized identifiers (NDC/NADA/ANADA) and package metadata from regulator listings.

Identifiers
ANADA: 200771 ANADA: 200814 NADA: 141292 NDC Package: 11695-7048-1 NDC Package: 11695-7049-1 NDC Package: 17033-225-10 NDC Package: 17033-250-10 NDC Package: 51311-044-30 NDC Package: 51311-044-40 NDC Package: 55529-170-02 NDC Package: 55529-170-14 NDC Package: 86032-064-01 NDC Package: 86101-059-11 NDC Package: 86101-060-11 NDC Package: 86136-157-36 NDC Package: 86136-158-36 NDC Product: 11695 NDC Product: 17033 NDC Product: 51311 NDC Product: 55529 NDC Product: 86032 NDC Product: 86101 NDC Product: 86136
Package NDC Product NDC Form / Route Status
11695-7048-1 11695 -
11695-7049-1 11695 -
17033-225-10 17033 -
17033-250-10 17033 -
51311-044-30 51311 -
51311-044-40 51311 -
55529-170-02 55529 -
55529-170-14 55529 -
86032-064-01 86032 -
86101-059-11 86101 -
86101-060-11 86101 -
86136-157-36 86136 -
86136-158-36 86136 -

Enriched Documents

Documents are tiered by source trust: Official, Clinical, Manufacturer, Marketing.

  • Felanorm SPL • Structured Product Label • Official
    FDA Structured Product Label from the electronic animal drug product listing directory.
  • ReguZol SPL • Structured Product Label • Official
    FDA Structured Product Label from the electronic animal drug product listing directory.
  • Methimazole SPL • Structured Product Label • Official
    FDA Structured Product Label from the electronic animal drug product listing directory.
  • Felimazole SPL • Structured Product Label • Official
    FDA Structured Product Label from the electronic animal drug product listing directory.
  • Felanorm SPL • Structured Product Label • Official
    FDA Structured Product Label from the electronic animal drug product listing directory.
  • Methimazole SPL • Structured Product Label • Official
    FDA Structured Product Label from the electronic animal drug product listing directory.
  • Methimazole SPL • Structured Product Label • Official
    FDA Structured Product Label from the electronic animal drug product listing directory.
  • Felanorm SPL • Structured Product Label • Official
    FDA Structured Product Label from the electronic animal drug product listing directory.
  • FOI Summary oA 200-771 Approved July 8, 2024.pdf • FOI summary • Official • Jan. 26, 2026
    FDA FOI summary for application 200771
  • FOI Summary oA 200-814 Approved June 27, 2025.pdf • FOI summary • Official • July 1, 2025
    FDA FOI summary for application 200814
  • UCM165091.pdf • FOI summary • Official • Aug. 8, 2019
    FDA FOI summary for application 141292

Data Sources & Change Log

Every non-trivial field is expected to include provenance and update timestamps.

Official 124 Clinical 7 Manufacturer 0 Marketing 0
Current Field Facts
  • overdose_info: Overdose may intensify side effects and can lead to overt hypothyroidism. Supportive care is required if an overdose occurs. (Clinical, 2026-04-12)
  • overdose_info: Overdose may intensify side effects and can lead to overt hypothyroidism. Supportive care is required if an overdose occurs. (Clinical, 2026-04-11)
  • overdose_info: Overdose may intensify side effects and can lead to overt hypothyroidism. Supportive care is required if an overdose occurs. (Clinical, 2026-02-12)
  • side_effects: Vomiting, decreased appetite, lethargy, facial itching. Rare: low blood cell counts. (Clinical, 2026-04-11)
  • storage_handling: Store at room temperature. (Clinical, 2026-04-12)
  • storage_handling: Store at room temperature. (Clinical, 2026-04-11)
  • storage_handling: Store at room temperature. (Clinical, 2026-02-12)
  • contraindications: Use caution with liver disease, blood disorders, or autoimmune conditions. (Official, 2026-04-12)
  • contraindications: Use caution with liver disease, blood disorders, or autoimmune conditions. (Official, 2026-04-11)
  • contraindications: Use caution with liver disease, blood disorders, or autoimmune conditions. (Official, 2026-02-12)
  • indications: For the treatment of hyperthyroidism in cats. (Official, 2026-06-22)
  • indications: For the treatment of hyperthyroidism in cats. (Official, 2026-06-22)
  • indications: For the treatment of hyperthyroidism in cats. (Official, 2026-06-21)
  • indications: For the treatment of hyperthyroidism in cats. (Official, 2026-06-20)
  • indications: For the treatment of hyperthyroidism in cats. (Official, 2026-06-13)
  • indications: For the treatment of hyperthyroidism in cats. (Official, 2026-06-12)
  • indications: For the treatment of hyperthyroidism in cats. (Official, 2026-06-12)
  • indications: For the treatment of hyperthyroidism in cats. (Official, 2026-06-11)
  • indications: For the treatment of hyperthyroidism in cats. (Official, 2026-06-11)
  • indications: For the treatment of hyperthyroidism in cats. (Official, 2026-06-10)
Recent Revisions
  • side_effects updated 2026-04-12 10:05 by etl_backfill • Backfilled from existing medication fields
  • contraindications updated 2026-04-12 10:05 by etl_backfill • Backfilled from existing medication fields
  • usage updated 2026-04-12 10:05 by etl_backfill • Backfilled from existing medication fields
  • side_effects updated 2026-04-11 10:05 by etl_backfill • Backfilled from existing medication fields
  • contraindications updated 2026-04-11 10:05 by etl_backfill • Backfilled from existing medication fields
  • usage updated 2026-04-11 10:05 by etl_backfill • Backfilled from existing medication fields
  • side_effects updated 2026-02-12 19:40 by etl_backfill • Backfilled from existing medication fields
  • contraindications updated 2026-02-12 19:40 by etl_backfill • Backfilled from existing medication fields
  • usage updated 2026-02-12 19:40 by etl_backfill • Backfilled from existing medication fields

FDA Products & Applications (Animal Drugs @ FDA)

Official sponsor/proprietary-name/application-status records linked by active ingredient.

Product Sponsor Application Status Published
Felanorm®
RX
Methimazole
Oral Solution • Oral
Label highlights
Official documents
Virbac AH, Inc. ANADA 200-771 Approved Jan 26, 2026
Methimazole Coated Tablets
RX
Methimazole
Coated Tablets • Oral
Label highlights
Official documents
Felix Pharmaceuticals Pvt. Ltd. ANADA 200-814 Approved Jul 1, 2025
Felimazole®
RX
Methimazole
Coated Tablets • Oral
Label highlights
Official documents
Dechra, Ltd. NADA 141-292 Approved Aug 8, 2019

Data source: FDA Animal Drugs @ FDA (public search export).

What It's For (FDA Label Highlights)

Extracted from FDA Animal Drugs @ FDA product labeling. Always confirm details with your veterinarian.

Composition / specifications
5 mg/mL
Cats
Indication

For the treatment of hyperthyroidism in cats.

Dosage

The starting dose is 2.5 mg administered every 12 hours. Following 3 weeks of treatment, the dose should be titrated to effect based on individual serum total T4 (TT4) levels and clinical response. Dose adjustments should be made in 2.5 mg increments. The maximum total dosage is 20 mg per day divided, not to exceed 10 mg as a single administration.

Limitations

FDA page: Open in Animal Drugs @ FDA

Composition / specifications
2.5 mg or 5 mg methimazole per tablet
Cats
Indication

For the treatment of hyperthyroidism in cats.

Dosage

The starting dose of Methimazole Coated Tablets is 2.5 mg administered every 12 hours. Following 3 weeks of treatment, the dose should be titrated to effect based on individual serum total T4 (TT4) levels and clinical response. Dose adjustments should be made in 2.5 mg increments. The maximum total dosage is 20 mg per day divided, not to exceed 10 mg as a single administration.

Limitations

FDA page: Open in Animal Drugs @ FDA

Species: Cat
Cats
Indication
For the treatment of hyperthyroidism in cats.
Dosage
The starting dose is 2.5 mg administered every 12 hours. Following three weeks of treatment, the dose should be titrated to effect based on individual serum total T4 (TT4) levels and clinical response. Dose adjustments should be made in 2.5 mg increments. The maximum total dosage is 20 mg per day divided, not to exceed 10 mg as a single administration.
Limitations
Due to potentially serious adverse reactions such as hepatopathy, immune-mediated anemia, thrombocytopenia, and agranulocytosis, cats on methimazole therapy should be monitored closely for any sign of illness including anorexia, vomiting, head/facial pruritus or edema, depression/lethargy, weight loss, anemia, skin lesions, diarrhea, fever, or lymphadenopathy. If a cat becomes ill while on FELIMAZOLE Coated Tablets, the drug should be stopped and appropriate hematological and biochemical testing should be done (see ANIMAL SAFETY and POST APPROVAL EXPERIENCE).

FDA page: Open in Animal Drugs @ FDA

Usage

Used to manage hyperthyroidism in cats.

Source: FDA Animal Drugs @ FDA • Reference

Contraindications

Use caution with liver disease, blood disorders, or autoimmune conditions.

Side Effects

Vomiting, decreased appetite, lethargy, facial itching. Rare: low blood cell counts.

Source: FDA openFDA • Reference

Top Reported Reactions (openFDA)

De-duplicated reaction terms grouped by body system from FDA openFDA reports (not verified; does not prove causation).

Digestive
Loss of appetite (1) • Cat Decreased appetite (1) • Cat

Showing top 5 for Digestive.

Neurologic
Unsteady walking (1) • Cat

Showing top 5 for Neurologic.

Behavior
Behavioral disorder (1) • Cat

Showing top 5 for Behavior.

Other
Haematuria (1) • Cat Glucosuria (1) • Cat General illness (1) • Cat Gait abnormality (1) • Cat Fracture (1) • Cat
Show more (23)
Fever (1) • Cat Eye disorder NOS (1) • Cat Epistaxis (1) • Cat Elevated symmetrical dimethylarginine (1) • Cat Elevated protein:creatinine ratio (1) • Cat Elevated creatinine (1) • Cat Elevated alanine aminotransferase (1) • Cat Distress (1) • Cat Dermatitis (1) • Cat Dehydration (1) • Cat Defect Unknown/Not Specified (1) • Cat Decreased urine concentration (1) • Cat Decreased haematocrit (1) • Cat Death by euthanasia (1) • Cat Death (1) • Cat Confusion (1) • Cat Bruising (1) • Cat Bronchopulmonary inflammation (1) • Cat Azotaemia (1) • Cat Anaemia NOS (1) • Cat Abnormal radiograph finding (1) • Cat Abnormal movement NOS (1) • Cat Abdominal pain (1) • Cat

Showing top 5 for Other.

Data source: FDA openFDA Animal & Veterinary adverse event reports.

Adverse Event Case Summaries (openFDA)

These are individual FDA adverse event reports. They are unverified and do not prove the medication caused the reaction.

Cat, Domestic Shorthair, Male, 13 year, 6.876 kilogram • Drug: MSK, Unassigned, Unknown • Reactions: Fever, Not eating, Neutrophilia, Monocytosis, Immune mediated haemolytic anaemia… • Outcome: Ongoing

  • Report ID: USA-USFDACVM-2025-US-074332
  • Serious AE: Yes
  • Treated For AE: Yes
  • Sex: Male
  • Age: 13.00 Year
  • Weight: 6.876 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
  • Form: Unassigned
Reactions Reported:
Fever Not eating Neutrophilia Monocytosis Immune mediated haemolytic anaemia Behavioral disorder (unspecified) Decreased haematocrit
Outcomes: Ongoing

Cat, Domestic Mediumhair, Male, 20 year, 3.42 kilogram • Drug: MSK, Unknown • Reactions: Vomiting • Outcome: Ongoing

  • Report ID: USA-USFDACVM-2025-US-073853
  • Serious AE: No
  • Treated For AE: No
  • Sex: Male
  • Age: 20.00 Year
  • Weight: 3.420 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
Reactions Reported:
Vomiting
Outcomes: Ongoing

Cat, Domestic Shorthair, Female, 16 year, 4.128 kilogram • Drug: MSK, Unassigned, Unknown • Reactions: Seizure NOS, Wobbliness, Inappropriate elimination NOS, Vocalisation, Distress… • Outcome: Ongoing

  • Report ID: USA-USFDACVM-2025-US-072860
  • Serious AE: Yes
  • Treated For AE: No
  • Sex: Female
  • Age: 16.00 Year
  • Weight: 4.128 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
  • Form: Unassigned
Reactions Reported:
Seizure NOS Wobbliness Inappropriate elimination NOS Vocalisation Distress Behavioral disorder (unspecified) Head twitching Eye disorder NOS Confusion Abnormal movement NOS
Outcomes: Ongoing

Cat, Domestic Shorthair, Female, 15 year, 5.4 kilogram • Drug: MSK, Solution, Oral, Dose: 0.65 mL per dose, Frequency: 12 per hour • Reactions: Vomiting, Behavioral disorder (unspecified), UNPALATABLE • Outcome: Outcome Unknown

  • Report ID: USA-USFDACVM-2025-US-074045
  • Serious AE: No
  • Treated For AE: No
  • Sex: Female
  • Age: 15.00 Year
  • Weight: 5.400 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Oral
  • Form: Solution
  • Dose: 0.65 mL per dose
  • Frequency: 12 per hour
Reactions Reported:
Vomiting Behavioral disorder (unspecified) UNPALATABLE
Outcomes: Outcome Unknown

Cat, Domestic Shorthair, Female, 9 year, 3.175 kilogram • Drug: MSK, Solution, Oral, Dose: 5 Milligram per animal, Frequency: 12 per hour • Reactions: Reddening of the skin, Itching, Localised hair loss, Skin irritation • Outcome: Outcome Unknown

  • Report ID: USA-USFDACVM-2025-US-074043
  • Serious AE: Yes
  • Treated For AE: Yes
  • Sex: Female
  • Age: 9.00 Year
  • Weight: 3.175 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Oral
  • Form: Solution
  • Dose: 5 Milligram per animal
  • Frequency: 12 per hour
Reactions Reported:
Reddening of the skin Itching Localised hair loss Skin irritation
Outcomes: Outcome Unknown

Cat, Domestic Mediumhair, Male, 17 year, 4.536 kilogram • Drug: MSK, Unassigned, Unknown • Reactions: Medication error NOS, Skin lesion NOS, Dermatitis, Vomiting • Outcome: Ongoing

  • Report ID: USA-USFDACVM-2025-US-073128
  • Serious AE: Yes
  • Treated For AE: Yes
  • Sex: Male
  • Age: 17.00 Year
  • Weight: 4.536 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
  • Form: Unassigned
Reactions Reported:
Medication error NOS Skin lesion NOS Dermatitis Vomiting
Outcomes: Ongoing

Cat, Domestic Shorthair, Female, 19.5 year, 4.454 kilogram • Drug: MSK, Solution, Unknown • Reactions: Glucosuria • Outcome: Outcome Unknown

  • Report ID: USA-USFDACVM-2025-US-073329
  • Serious AE: No
  • Treated For AE: Yes
  • Sex: Female
  • Age: 19.50 Year
  • Weight: 4.454 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
  • Form: Solution
Reactions Reported:
Glucosuria
Outcomes: Outcome Unknown

Cat, Siberian, Female, 15 year, 5.4 kilogram • Drug: MSK, Solution, Oral, Dose: 2.50 Milligram per dose, Frequency: 1 per day • Reactions: Vomiting, Defect Unknown/Not Specified • Outcome: Recovered/Normal

  • Report ID: USA-USFDACVM-2025-US-072611
  • Serious AE: No
  • Treated For AE: No
  • Sex: Female
  • Age: 15.00 Year
  • Weight: 5.400 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Oral
  • Form: Solution
  • Dose: 2.50 Milligram per dose
  • Frequency: 1 per day
Reactions Reported:
Vomiting Defect Unknown/Not Specified
Outcomes: Recovered/Normal

Data source: FDA openFDA Animal & Veterinary adverse event reports.

Overdose Information

Overdose may intensify side effects and can lead to overt hypothyroidism. Supportive care is required if an overdose occurs.

Storage & Handling

Store at room temperature.

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