What is known about ivermectin toxicity from accidental ingestion of veterinary products in emergency department reports?
Executive summary
Emergency-department and poison-center reports have documented a rise in ivermectin toxicity tied to people ingesting veterinary formulations or taking excessive doses for COVID-19 prevention or treatment; these cases commonly present with gastrointestinal and neurologic effects and are usually managed with supportive care, though hospitalizations and at least one death have been reported [1] [2] [3]. Veterinary products intended for large animals are more concentrated and contain inactive ingredients not evaluated for humans, and patients who took veterinary formulations tended to ingest higher doses and have more altered mental status than those taking prescription tablets [4] [1].
1. The pattern seen in emergency and poison‑center reports
Retrospective case series and poison center summaries collected during the pandemic show clusters of exposures: for example, a 24‑week Oregon Poison Center review found most patients required healthcare visits, with 21 hospitalized and 13 treated in emergency departments; among those cases 17 had ingested veterinary formulations and 15 prescription tablets, and ingestion was often motivated by attempts to prevent or treat COVID‑19 [1]. National alerts and surveillance noted increases in poison center calls and retail dispensing of ivermectin compared with pre‑pandemic baselines, with veterinary product use particularly prominent in 2021 reporting [4] [2].
2. Typical clinical presentation in these reports
Clinical effects reported across emergency and poison‑center data cluster into gastrointestinal symptoms (nausea, vomiting, abdominal pain, diarrhea) at lower or moderate overdoses and central nervous system effects — altered mental status, ataxia, seizures, coma — at higher doses, reflecting case descriptions and public‑health advisories [3] [5]. In one multi‑case summary, 30 patients had neurotoxicity, 14 had GI complaints, and musculoskeletal complaints were noted in seven; onset was often rapid after a large single dose and sometimes gradual after repeated misuse [1] [2].
3. Dose, formulation and risk factors that emerge from the data
Reports consistently identify higher ingested doses and veterinary formulations as risk factors for more severe neurologic toxicity: veterinary pastes and solutions marketed for horses and livestock can deliver much larger milligram amounts per use than human tablet dosing, and reported veterinary doses in case series ranged from single‑dose paste exposures of about 6.8 mg up to 125 mg and solutions of 20–50 mg in some patients [2] [1]. Public‑health notices explain that these animal products are concentrated for large animals and may include inactive ingredients untested in humans, amplifying overdose risk [4] [6].
4. Treatment and clinical outcomes reported in emergency settings
Emergency‑department management described in reviews and toxicology guidance is largely supportive: decontamination with activated charcoal may be considered for large oral ingestions if the patient is appropriate for it, and most human case reports improved with supportive care and time; no specific, consistently proven antidote is documented for humans, and experimental veterinary treatments like intravenous lipid emulsion have mixed evidence and limited human data [5] [3]. Case series include hospitalizations for confusion, ataxia, hypotension and seizures and report at least one death in the reviewed cohorts, underscoring that while many patients recover with care, severe outcomes can occur [1] [7].
5. Limitations, open questions and competing narratives
Available publications are predominantly retrospective case series, poison‑center reports and clinical case reports that can identify associations but cannot quantify population risk or causal dose‑response precisely; they also reflect a pandemic period with heightened off‑label use that may bias case mix toward large‑dose veterinary exposures [1] [2]. Regulatory and scientific bodies have emphasized lack of evidence for ivermectin in COVID‑19 and warned against veterinary product use, but some advocates continue to promote off‑label human dosing — a competing narrative that likely contributed to increased exposures reported by poison centers [2] [4]. The literature also documents veterinary‑species and genetic sensitivity issues (e.g., MDR1/ABCB1 in dogs) that illustrate mechanisms of neurotoxicity but cannot be directly mapped onto human susceptibility without further study [8] [9].