How have veterinary ivermectin poisoning cases been documented in poison control and emergency department data?
Executive summary
Poison control centers and emergency departments documented a clear uptick in human exposures to ivermectin during the COVID-19 era, with multiple case series and surveillance projects showing that many of those exposures involved veterinary formulations and in some instances produced hospitalizations and severe neurologic effects [1] [2] [3]. Public-health and toxicology groups have compiled case reports and aggregated poison‑center call data to characterize who was affected, what products were used, and the clinical consequences, while acknowledging limitations in passive surveillance and causality [4] [5].
1. Rising call volumes: national poison‑center systems recorded a spike
Beginning in 2021, poison control centers reported a multi‑fold increase in calls for human ivermectin exposures compared with pre‑pandemic baselines, with some states and national summaries describing three‑fold or greater rises in call volume and media reporting of clusters such as 17 cases tracked in Wisconsin [1] [6] [7]. Professional toxicology consortia and public health agencies echoed that trend: the ACMT’s ToxIC/FACT pharmacovigilance project and CDC‑linked reporting described surges in reports of adverse events tied to ivermectin misuse for COVID‑19 prevention or treatment [2] [5].
2. Veterinary versus human formulations: how records distinguish sources
Poison‑center and ED case series repeatedly note that a substantial share of exposures involved veterinary products rather than prescription human tablets; in the Oregon Poison Center series 17 of 32 healthcare‑visit cases implicated veterinary formulations while 15 involved prescription tablets [4]. State health advisories and poison‑center guidance point out that veterinary products—especially “sheep drench,” horse paste, and concentrated pour‑on or injectable formulations—are far more concentrated or include inactive ingredients not evaluated for human use, which contributes to risk when consumed by people [8] [1] [7].
3. Clinical picture in poison‑center and ED data: neurologic and supportive‑care patterns
Clinical data culled from poison‑center consults and ED admissions show a pattern of gastrointestinal symptoms at lower excess doses and central nervous system depression, ataxia, dizziness, or even respiratory failure in larger overdoses; management reported in the toxicology literature is primarily supportive care [9] [2]. The Oregon series described mostly older men ingesting higher than recommended doses, with many hospitalized and at least one death in a separate dataset; nationally, some reports described hospitalizations—six of 21 in one NEJM‑published case set—and cases of severe toxicity submitted to ToxIC [3] [4] [2].
4. Data sources, surveillance strengths and limits
Documentation comes largely from passive surveillance: poison‑center call logs, retrospective poison‑center case reviews, ED records, and voluntary reporting to toxicology consortia, which allow rapid detection of trends but have known limitations including underreporting, variable case confirmation, inconsistent dose/ product data, and inability to prove causation in every case [4] [2] [5]. Papers and state advisories explicitly state that while trends are clear, the datasets are heterogeneous—mixing self‑reported doses, different formulations, and varying clinical thresholds for presentation—so numerical tallies likely under‑ or misestimate total harms [4] [1].
5. Competing narratives and institutional responses
Public‑health bodies (FDA, state health departments), professional toxicology and veterinary organizations documented the same surveillance signal and issued warnings against off‑label human use of veterinary ivermectin, framing the increase as a preventable harm linked to misinformation about COVID‑19 therapeutics [2] [5] [8]. At the same time, reporting sometimes conflated veterinary product use with all ivermectin exposures and varied in emphasis between sensational case counts and measured clinical analyses; the surveillance groups themselves emphasize the need for careful interpretation of passive reports and for clinicians to report cases to poison centers to improve data quality [9] [10].
6. Bottom line: what the records show and what they cannot
Poison‑control and ED data unequivocally document an increase in human ivermectin exposures during the pandemic, with a notable proportion involving veterinary products and a subset causing hospitalization and severe neurologic effects, and these findings are consistent across state poison centers, published case series, and toxicology consortium reports [1] [4] [2]. What the assembled surveillance cannot fully resolve are precise incidence rates, exact causal pathways in every individual case, and long‑term outcomes—limitations acknowledged in the primary reports and advisories [4] [5].