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Are there any reported cases of ivermectin toxicity in humans due to incorrect formulation use?
Executive summary
Published case series and toxicology reports confirm human poisonings from misuse of veterinary or nonstandard ivermectin formulations, with hospitalized patients showing severe neurological and gastrointestinal effects; one New England Journal of Medicine case series described 21 people with toxic effects and 6 hospitalizations after inappropriate ivermectin use [1]. Regulatory bodies and reviews warn that veterinary formulations differ from human products and have not been tested for human safety [2] [3].
1. Reported human poisonings after using veterinary or incorrect ivermectin formulations
Clinical and public-health literature documents multiple instances in which people ingested veterinary ivermectin or took human formulations in nonstandard ways and developed toxicity: the New England Journal of Medicine summarized 21 people who had used veterinary products or taken excessive human doses, reporting symptoms from confusion and ataxia to seizures and hypotension and noting six hospitalizations among those cases [1]. Toxicology reviews and case reports likewise list rash, edema, headache, dizziness, nausea, vomiting, diarrhea and asthenia after accidental or intentional exposure to veterinary formulations [4] [5].
2. How formulations and dosing differ — why misuse causes risk
Authorities emphasize that veterinary ivermectin products are formulated and dosed for animals (pour-on, injectables, pastes, drench solutions) and are not tested for human safety; the FDA and fact-checkers repeatedly warn humans should not use animal products because concentrations, excipients and intended routes differ and can result in toxic exposures [2] [3]. MedicineNet and other drug references state that veterinary formulations can be highly toxic to humans and explicitly advise against ingesting, injecting or otherwise using animal ivermectin [6] [4].
3. The spectrum of reported toxic effects and their severity
The documented clinical picture ranges from gastrointestinal upset and dizziness to serious neurologic events. The NEJM series highlighted severe episodes including confusion, ataxia, seizures and hypotension in people misusing ivermectin [1]. Postmarketing and clinical-trial data also record dizziness, somnolence and tremor as recognized adverse effects in humans; rare but serious neurologic events have been reported in other contexts [7] [8].
4. Toxic dose context and species differences — what the lab data say
Preclinical toxicology gives a wide LD50 range across species, with mice and dog data extrapolated to human-equivalent doses that are much higher than standard approved human doses for parasitic infections [9] [10]. However, laboratory-to-human extrapolations are imperfect: human susceptibility is mediated by blood–brain barrier transporters like P‑glycoprotein (MDR1), and genetic or disease-related differences can increase CNS exposure and risk [11] [7].
5. The role of the COVID‑19 controversy and policy changes in driving misuse
Several sources link spikes in human use of inappropriate ivermectin products to interest during COVID‑19, with prescriptions and attempts to obtain animal formulations rising and some jurisdictions changing access rules; public-health bodies cautioned that available clinical-trial evidence did not support ivermectin for COVID‑19 and warned against using animal products [1] [12] [13]. Journalists and fact‑checkers documented misinformation and repeated warnings that “animal ivermectin should not be used on humans” [3].
6. What authorities and reviews recommend
The FDA and medical reviewers advise that ivermectin approved for humans be used only at indicated doses and that animal formulations not be used by people; WHO and manufacturers have discouraged routine off‑label use for COVID‑19 outside clinical trials [2] [12]. Toxicology and clinical reviews recommend avoiding self‑medication with veterinary products and emphasize that misuse can cause life‑threatening adverse effects [6] [5].
7. Uncertainties, gaps, and alternative perspectives
Available sources document case series and toxicology signals but do not provide a single comprehensive national count of all poisonings from misuse; larger epidemiologic surveillance data on total numbers and long‑term outcomes are not detailed in these reports (not found in current reporting). Some systematic reviews and meta-analyses examined ivermectin’s potential benefits for COVID‑19 with mixed conclusions about efficacy, but safety concerns from misuse of veterinary formulations remain distinct from debates over ivermectin’s clinical benefit in controlled human dosing [14] [12].
8. Bottom line for clinicians, pharmacists and the public
Do not use veterinary ivermectin formulations in people; documented cases show real harms when animal products or excessive/nonstandard doses are taken by humans, and regulators explicitly warn the safety of animal formulations in humans is unknown [2] [1] [3]. When questions arise after exposure, clinicians should treat symptoms, report cases to poison-control and public‑health authorities, and advise patients to obtain human medicines only through legitimate prescriptions and pharmacies [2] [6].
If you want, I can pull the exact NEJM case-series details (dates, locations, ages) from the paper or summarize official FDA consumer guidance language verbatim as cited above [1] [2].