Drug profile

The FDA adverse-event record for Monensin

265 FDA reports name Monensin, a high-volume drug in the CVM extract. Species, reactions, and outcomes follow.

#458 of 2,679
by report volume (all drugs)
265
adverse-event reports
52.1%
death-coded share
Cattle
most-reported species

Corpus placement

According to the FDA Center for Veterinary Medicine openFDA adverse-event extract, Monensin ranks #458 of 2679 by total reports (265) and #55 of 1130 by death-coded share (52.1%). 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)
#458
This drug, reports of 2679
#55
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. Monensin has 265 reports now versus 261 in that prior snapshot: 4 more (1.5%).

Report change
+4
Death-coded reports
+3
Death-coded share
+0.4 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 Monensin changes

Signature read: death-coded report count at 138 is the most distinctive stamp on Monensin's FDA AER row.

Important: Adverse event reports do not establish that a drug caused or contributed to the event. Consult your veterinarian before making treatment decisions.
265
Total Reports
138
Deaths Reported
52.1%
Death-coded share of reports

Active Ingredients

Monensin

Administration Routes

OralUnknownOphthalmic

Species Affected

Cattle 193
Turkey 26
Chicken 14
Horse 10
Goat 7
Dog 4
Other 2
Sheep 2
Other Birds 2
Unknown 2

Most Affected Breeds

Crossbred Bovine/Cattle 76
Cattle (unknown) 38
Holstein-Friesian also known as Holstein 35
Turkey (unknown) 25
Unknown 17
Chicken (unknown) 14
Cattle (other) 10
Horse (unknown) 7
Jersey 7
Aberdeen Angus 7

Most Reported Reactions

Death 126
Anorexia 61
Diarrhoea 59
Lack of efficacy (protozoa) - Coccidia 50
Accidental exposure 43
Recumbency 30
Inappropriate preparation of medication 24
Bloody diarrhoea 19
Milk production decrease 18
Depression 12
PR-HEART, LESION(S) 11
Alteration of milk quality 11

Outcome Breakdown

Died
137 (77.0%)
Outcome Unknown
30 (16.9%)
Recovered/Normal
6 (3.4%)
Euthanized
3 (1.7%)
Ongoing
2 (1.1%)

Monensin: high death-coded share 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 Monensin, both floored at ≥50 reports so the neighborhoods stay in the advertised mass.

What to do with this drug

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

openFDA Animal & Veterinary Adverse Events (FDA CVM) for Monensin (#458 of 2,679 by report volume); death-coded 52.1%. PlainBreed drug row · death-coded report count stamp 138 · vintage 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 →