Drug profile
The FDA adverse-event record for Methimazole
1,168 FDA reports name Methimazole, a high-volume drug in the CVM extract. Species, reactions, and outcomes follow.
- #160 of 2,679
- by report volume (all drugs)
- 1,168
- adverse-event reports
- 13.5%
- death-coded share
- Cat
- most-reported species
Corpus placement
According to the FDA Center for Veterinary Medicine openFDA adverse-event extract, Methimazole ranks #160 of 2679 by total reports (1,168) and #413 of 1130 by death-coded share (13.5%). National dual: Milbemycin Oxime + Spinosad is #1 of 2679 drugs by total adverse-event reports (149,624) at death-coded-share rank 965 of 1130 drugs with at least 50 reports (2.3%); separately, Atlantic Salmon Transgenic Whole (Opafp-Ghc2 Rdna Construct Inserted Into The A-Locus In The Eo-1A Lineage) is #1 highest death-coded share at 97.8% (report rank #821).
- 149,624
- Milbemycin Oxime + Spinosad reports (#1)
- 97.8%
- Atlantic Salmon Transgenic Whole (Opafp-Ghc2 Rdna Construct Inserted Into The A-Locus In The Eo-1A Lineage) death share (#1)
- #160
- This drug, reports of 2679
- #413
- This drug, death share of 1130
Report volume reflects how common a breed or drug is and how often owners and vets file — not actual risk. Death-coded share ranks are limited to entries with enough reports to be meaningful. The two maps do not agree at #1.
Release-over-release change
What changed in the latest FDA data snapshot
PlainBreed reconstructed the prior snapshot from dated openFDA partitions through 2025 Q4, then compared it with the 2026-07-27 openFDA export. Methimazole has 1,168 reports now versus 1,114 in that prior snapshot: 54 more (4.8%).
- Report change
- +54
- Death-coded reports
- +0
- Death-coded share
- −0.7 pts
This compares reported-event counts in two source snapshots. It does not establish a change in real-world risk, product safety, or disease incidence.
Subscribe to Methimazole changesSignature read: death-coded report count at 158 is the most distinctive stamp on Methimazole's FDA AER row.
Active Ingredients
Administration Routes
Species Affected
Most Affected Breeds
Most Reported Reactions
Outcome Breakdown
Methimazole: high report volume in the FDA AER row
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.
High-volume nationwide drug peers
Two openFDA-derived peer sets for Methimazole, both floored at ≥50 reports so the neighborhoods stay in the advertised mass.
Similar report volume
Nearest other drugs by FDA report count (1,168 here).
Similar death-coded share
Nearest other drugs by death-coded share (13.5% here), distinct from the volume row.
What to do with this drug
- Compare Methimazole's report volume and death-coded share against similar drugs nationwide. See similar drugs
- Read how death-coded share differs from a mortality rate before drawing conclusions. Understanding adverse events
- Browse the full drug directory to compare report counts across products. All drugs
A report does not prove a drug caused the reaction; consult a veterinarian before acting on this data.
Source: FDA Center for Veterinary Medicine openFDA Animal & Veterinary Adverse Events (CVM AER) · 2025
Informational only. FDA adverse-event reports are voluntary and do not prove causation; consult a veterinarian before acting on them. Verify with FDA CVM →