Are there documented cases or clinical reports of human harm from accidental ingestion of veterinary ivermectin products, and what doses were involved?
Executive summary
Documented clinical reports and poison‑center series do show human harm from accidental or intentional ingestion of veterinary ivermectin products, including hospitalizations and at least one published fatal transdermal‑overdose case with a measured plasma level of 27 ng/mL (fatal case report) [1]. Larger surveillance reports and poison‑center case series from the pandemic period describe dozens of exposures, multiple hospitalizations, neurological and gastrointestinal toxicity, and one series that identified higher toxicity among those taking veterinary formulations [2] [3] [4].
1. What the published case literature shows: a rare fatality with measured drug level
A peer‑reviewed case report and literature review describes a fatal case of transdermal ivermectin misuse in which the patient’s plasma concentration was 27 ng/mL; authors conclude the patient suffered ivermectin poisoning with progressive gastrointestinal symptoms followed by diffuse cerebral edema and intracranial hypertension [1] [5]. That report frames fatalities as uncommon but documents that severe outcomes, including death, can occur when ivermectin is misused in nonstandard routes or formulations [1].
2. Poison center series and clinical toxicology reports: dozens of harmful exposures, many linked to veterinary products
Multiple poison‑center reports during 2020–2022 documented sharp increases in ivermectin exposures tied to COVID‑19 claims. An Oregon Poison Center letter described 21 calls in one month with six hospitalizations; many of those involved ingesting veterinary injectable or topical products, and symptoms were mainly neurologic and gastrointestinal [2]. A clinical toxicology case series identified 37 cases of ivermectin toxicity: 17 involved veterinary formulations, most patients were hospitalized [6], neurotoxicity occurred in 30 patients, and one death was reported; the authors note patients taking veterinary products took higher doses and had more altered mental status [3].
3. Public‑health surveillance and poison‑control trends: increased calls and higher doses from animal formulations
Health departments and media covering poison‑control data reported five‑fold or more increases in calls and large upticks in dispensing and misuse; Wisconsin tracked 17 cases in 2021, and national poison‑center data showed a major rise in calls tied to animal formulations sold at livestock supply centers [4] [7]. Public‑health advisories from the CDC and state health departments warned veterinary products are formulated at much higher concentrations for large animals, which “may result in overdoses when used by humans” [8] [9] [10].
4. Typical human therapeutic doses vs. doses implicated in toxicity
Standard human therapeutic dosing for parasitic indications is weight‑based (for example, single oral doses around 150–200 µg/kg for some indications), which industry and regulatory sources say is safe in humans; by contrast, achieving ivermectin concentrations that inhibit SARS‑CoV‑2 in vitro would require massively higher oral dosing (an estimated 7.0 mg/kg, ~35× the maximum FDA‑approved human dose), a level the literature flags as toxic [11] [12]. Poison‑center analyses indicate those who ingested veterinary preparations generally consumed higher absolute doses than patients taking human prescription tablets and therefore had more severe neurotoxic presentations [3].
5. Typical clinical manifestations and outcomes reported
Across case series and advisories, reported adverse effects from overdose include nausea, vomiting, diarrhea, hypotension, allergic reactions, dizziness, ataxia, seizures, coma and, in rare cases, death; neurotoxicity (altered mental status) and gastrointestinal symptoms are repeatedly highlighted in the clinical reports [13] [3] [2]. Surveillance reports emphasize that many exposures involved misuse (intentional self‑medication) rather than purely accidental single‑tablet mistakes, though accidental ingestions of pet heartworm products have also been described in poison‑control counseling material [14].
6. Competing explanations, limitations, and gaps in reporting
Available sources show an association between veterinary‑formulation ingestion and more severe poisoning, but the literature is heterogeneous: many reports are poison‑center call summaries (subject to reporting bias), case series sample sizes are small, and toxicologic confirmation (measured plasma concentrations) is rare — the published fatal transdermal case is notable because it included a measured level [3] [1]. Available sources do not provide a large, systematic dose‑response dataset that quantifies precise human LD50 or threshold doses for every formulation (not found in current reporting).
7. What public health authorities advise and why
Regulators and professional bodies uniformly advise against using veterinary ivermectin in humans because veterinary products are more concentrated and not tested for human dosing or excipients; the FDA and state health alerts explicitly warn of overdose risks and list severe symptoms that can result [9] [8] [13]. Those authorities frame most harms as preventable misuse rather than inevitable adverse effects of appropriately prescribed human ivermectin [13] [15].
Bottom line: multiple poison‑center series and at least one peer‑reviewed fatal case document real human harm from misuse of veterinary ivermectin products, with hospitalizations and severe neuro‑gastrointestinal toxicity reported; veterinary formulations tend to produce higher consumed doses and worse outcomes, but comprehensive dose‑response data in humans remain limited [1] [3] [2].