Drug profile

The FDA adverse-event record for Thiamazole

623 adverse-event reports submitted to the FDA Center for Veterinary Medicine reference Thiamazole. See the species affected, top reactions, and outcomes below.

623
adverse-event reports
8.3%
death-coded share
Cat
most-reported species
142
Vomiting - top reaction
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Important: Adverse event reports do not establish that a drug caused or contributed to the event. Consult your veterinarian before making treatment decisions.
623
Total Reports
52
Deaths Reported
8.3%
Death Rate

Active Ingredients

Thiamazole

Administration Routes

OralUnknownTransdermalTopicalOtherAuricular (Otic)Intradermal

Species Affected

Cat 565
Unknown 38
Human 18
Dog 2

Most Affected Breeds

Domestic Shorthair 372
Cat (unknown) 73
Domestic Longhair 64
Unknown 56
Siamese 17
Maine Coon 11
Ragdoll 8
Russian 4
Cat (other) 4
Burmese 2

Most Reported Reactions

Vomiting 142
Weight loss 108
Lethargy (see also Central nervous system depression in 'Neurological') 69
Elevated alanine aminotransferase (ALT) 66
Lack of efficacy - NOS 49
Anorexia 47
Decreased appetite 45
Other abnormal test result NOS 37
Excoriation 35
Elevated blood urea nitrogen (BUN) 35
Low thyroxine (T4) 32
Pruritus 31

Outcome Breakdown

Outcome Unknown
332 (56.5%)
Recovered/Normal
163 (27.7%)
Ongoing
39 (6.6%)
Died
28 (4.8%)
Euthanized
24 (4.1%)
Recovered with Sequela
2 (0.3%)

Thiamazole Adverse Event Insights

623 reports name Thiamazole; 52 recorded a death outcome (8.3% of reported events, not a population-level mortality rate). Active ingredient: Thiamazole. Administration routes: Oral, Unknown, Transdermal, Topical.

By species: Cat (565 reports), Unknown (38 reports), Human (18 reports). By breed: Domestic Shorthair (372), Cat (unknown) (73), Domestic Longhair (64).

Leading clinical signs: Vomiting (142), Weight loss (108), Lethargy (see also Central nervous system depression in 'Neurological') (69), Elevated alanine aminotransferase (ALT) (66). Outcome, 588 coded reports: Outcome Unknown leads at 56.5%.

Read these counts as reporting volume, not risk: per our methodology, a widely-prescribed drug will rack up more raw FDA reports in a given year than a rarely-used one at an identical true rate, so we recommend comparing within similar-exposure products rather than across the full 2025 catalog.

Source: FDA Center for Veterinary Medicine openFDA Animal & Veterinary Adverse Events (CVM AER) · 2025

Every figure on PlainBreed is rendered directly from FDA openFDA adverse event data, no number is typed in by an editor. This page draws directly on FDA openFDA data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.