What are the documented adverse events and poison‑control trends linked to human use of veterinary ivermectin since 2020?
Executive summary
Human use of veterinary ivermectin since 2020 has been linked to a clear rise in poison‑center reports and clinically significant toxic effects, including hospitalizations, neurologic complications, and at least one reported death in case series and surveillance summaries [1][2][3]. The pattern is tied to higher-than-recommended dosing, use of veterinary formulations not evaluated for humans, and a surge in prescriptions and informal procurement during the COVID‑19 pandemic [4][5][6].
1. Rising calls and prescriptions: the epidemiology of exposure
Multiple surveillance sources documented sharp increases in human exposures reported to poison control centers during 2020–2021, with three‑ to five‑fold rises from baseline in some months and dramatic spikes in dispensing of human ivermectin prescriptions contemporaneous with those calls [1][6][4]. National and tribal health agencies flagged that 2021 saw more reports of adverse effects associated with ivermectin misuse than pre‑pandemic baselines, a trend mirrored by outreach from the FDA and CDC to warn clinicians and retailers [3][5].
2. Clinical spectrum: from mild symptoms to hospitalization and death
Case series and poison‑center aggregates show a spectrum of presentations: many callers reported gastrointestinal and neurologic complaints, while cohorts described high rates of emergency‑department visits and hospital admissions, including seizures, altered mental status, and coma in severe overdose cases; one systematic case collection recorded one death among identified cases [2][3][4]. In a focused Oregon report, six of 21 callers in a single month required hospitalization for toxic effects after using ivermectin for COVID‑19 prevention or treatment [7][4].
3. Veterinary products, dosing errors, and formulation hazards
A recurrent and specific driver of toxicity was ingestion of veterinary formulations—pastes, pour‑ons, injectables and drenches—that are more concentrated, contain inactive ingredients not tested in humans, and are not intended for oral human use; in reported poison‑center cases, many patients had obtained veterinary ivermectin, often ingesting single large doses or repeated high doses [5][8][2]. Reported ingested amounts in case reports ranged widely (e.g., 6.8 mg to 125 mg of paste; 20–50 mg of 1% solution), well above standard human dosing, and some human‑prescribed regimens used experimentally high frequencies that also correlated with adverse events [4][7].
4. Neurotoxicity and mechanistic concerns
Serious neurologic toxicity has been reported when doses exceed recommended human ranges or when non‑oral veterinary routes were used; a published case described neurotoxicity after an oral regimen >0.4 mg/kg/day combined with an intravenous bolus of a veterinary product, illustrating route‑ and dose‑dependent risk and the absence of safety data for parenteral veterinary administration in people [9]. Pharmacologic caution stems from ivermectin’s central nervous system effects at high concentrations and the lack of human pharmacokinetic data for many of the off‑label regimens pursued during the pandemic [9][10].
5. Who was affected and outcomes
Across studies and poison‑center reports, older adults—median ages in the 60s—and men predominated among those presenting with toxicity, with many hospitalizations clustered in this demographic; poison‑center data and case series repeatedly identify older, often male patients ingesting supra‑therapeutic doses [7][2]. While many adverse events were reversible with supportive care, documented hospitalizations and at least one death in systematic case reviews and surveillance notices underscore that serious, sometimes fatal outcomes occurred [2][3].
6. Public‑health response, messaging, and evidence gaps
Federal agencies (FDA, CDC) and poison‑control networks issued advisories emphasizing that ivermectin is FDA‑approved for certain parasitic infections but not for COVID‑19, urging against veterinary product use and highlighting poisoning risks; these communications were driven by surveillance spikes and by steep increases in outpatient dispensing of human ivermectin during 2021 [5][1][6]. Important limitations persist in the record: many reports are passive surveillance or small case series, causal linkage to specific formulations or long‑term outcomes is variably documented, and quantitative national fatality counts tied solely to veterinary ivermectin remain incompletely reported in the cited sources [3][2].
7. Bottom line
Documented adverse events since 2020 form a consistent narrative: increased exposures and poison‑center calls, a preponderance of older male patients ingesting high doses or veterinary formulations, frequent emergency visits and hospitalizations including neurologic toxicity, and agency warnings to stop using animal ivermectin for COVID‑19 prevention or treatment [1][2][5]. Surveillance limitations mean that while morbidity from misuse is convincingly elevated and sometimes severe, precise population‑level mortality attributable only to veterinary ivermectin is not fully captured in the available reporting [3][2].