What are documented clinical cases of human toxicity from veterinary ivermectin ingestion and their outcomes?
Executive summary
A multi-center review identified 37 cases of ivermectin toxicity reported during the COVID-19 era, with veterinary formulations implicated in a substantial proportion of severe presentations and one recorded death among the series [1]. Clinical manifestations were dominated by neurotoxicity — altered mental status, ataxia, seizures — frequently requiring emergency care or hospitalization, and most patients improved with supportive care [2] [3].
1. The scope: how many documented cases and where they came from
Analysts compiling reports from poison centers and case series documented 37–40 people with ivermectin-related adverse events during the COVID-19 period in a focused study, with most patients reported to emergency departments or admitted to hospital (21 hospitalized, 13 seen in ED in the 37-case series) [1] [2] [4]. Additional surveillance and case reports — including New England Journal of Medicine summaries and public health advisories — corroborate a marked rise in poison control contacts and emergency visits tied to ivermectin exposures during 2021 [5] [6] [7].
2. Veterinary formulations were overrepresented among severe cases
Patients who ingested veterinary ivermectin — sold as equine pastes, concentrates, or injectable solutions — tended to take larger absolute doses (single large doses or repeated large daily doses) and developed rapid-onset neurologic toxicity more often than those who took prescription human tablets, with 17 of the 37 cases involving veterinary products in the principal series [2] [8]. Public health agencies noted that veterinary products are more concentrated, contain inactive ingredients not evaluated for humans, and therefore pose heightened overdose risk when repurposed for people [7].
3. Clinical features: what toxicity looks like
Across reports, the dominant clinical picture was neurotoxicity: confusion, ataxia, loss of coordination, visual hallucinations, central nervous system depression and seizures; gastrointestinal symptoms (nausea, vomiting, abdominal pain) and musculoskeletal complaints were also repeatedly reported [2] [6]. Case reports of extreme exposure include an ICU admission after intravenous administration of veterinary ivermectin with measured serum ivermectin of 187.74 ng/mL; that patient experienced severe neurotoxicity but survived [9] [10].
4. Outcomes and treatments documented
Most published cases improved with supportive care and time, and typical management emphasized symptomatic support and, for large oral ingestions, consideration of activated charcoal; no widely accepted antidote exists and advanced therapies such as intravenous lipid emulsion have been used in animals and reported only anecdotally for humans [3]. In the 37-case series one death was recorded, while other series and NEJM correspondence reported multiple hospitalizations for serious effects including seizures, hypotension, coma and, rarely, death [1] [5] [6]. Toxic outcomes correlated with higher ingested doses, parenteral exposures, and likely coexisting vulnerabilities, although detailed risk stratification remains limited in the available reports [2] [9].
5. Patterns: acute high-dose versus chronic lower-dose exposure
Investigators distinguished acute high-dose ingestions — commonly involving veterinary products and producing rapid severe neurotoxicity — from chronic lower-dose misuse of human tablets, which tended to produce milder, more insidious symptoms after weeks of use (median chronic daily dose ~13.5 mg over 3.8 weeks) [2]. The implication is that dose and route drive severity, and that misuse to “prevent” or “treat” COVID-19 led to both patterns being clinically observed [8] [5].
6. Limits of the evidence and competing narratives
Available data are dominated by case series, poison center reports, and single-case publications rather than large prospective cohorts, leaving uncertainty about true incidence, population risk factors, and long-term outcomes beyond initial recovery; several summaries explicitly note that most evidence shows recovery with supportive care but severe events including seizures and death can occur [3] [6]. Public health messaging (New Mexico DOH, IHS, NEJM commentary) frames these harms in the context of misinformation-driven use during the pandemic, but the literature itself is limited to relatively small numbers and heterogeneous exposures, so broader epidemiologic conclusions require cautious interpretation [7] [5].