Are there documented cases of toxicity from taking horse ivermectin paste and what were the outcomes?
Executive summary
Documented cases show that people who self-administered veterinary (horse) ivermectin paste have experienced toxicity requiring medical attention, including hospitalization, with symptoms such as confusion, ataxia, seizures and hypotension; animal formulations explicitly warn they are not for human use [1] [2] [3]. Separately, horses given ivermectin overdoses or that react to appropriate doses can develop severe neurologic signs and, in at least one published equine case series, one horse was euthanized while others recovered with supportive care [4] [5].
1. What the public reports say: human poison center and clinical accounts
A clear, peer‑reviewed piece of evidence comes from calls to the Oregon Poison Center in August 2021: 21 ivermectin‑exposure reports were logged, 17 involving veterinary formulations (commonly called “horse paste”), and six of those callers required hospitalization for toxic effects; reported clinical features included severe confusion, ataxia, seizures and low blood pressure [1]. Major clinical and public‑health outlets summarized that the FDA and hospitals received multiple similar reports of people seeking medical care after self‑medicating with animal ivermectin, and clinicians warn that large amounts can be toxic or deadly for people [2] [6].
2. Why veterinary paste poses special risks for people
Veterinary ivermectin pastes are formulated and dosed for large animals and contain higher total amounts of ivermectin per syringe than human products; labels and manufacturers explicitly state they are for oral use in horses only and warn against human use, noting potential for severe personal injury or death [7] [3] [8]. Observers and clinicians have flagged additional unknowns — including differing base ingredients and absorption characteristics in paste or liquid animal formulations — that can increase the unpredictability of human blood levels compared with pharmaceutical human preparations [9] [3].
3. Clinical spectrum and outcomes in humans from available reporting
Available source reporting documents a range from mild to severe toxicity in people: the Oregon report lists neurologic presentations (confusion, ataxia, seizures) and hypotension and notes hospital admissions among exposed individuals [1], while clinical outreach pieces (Cleveland Clinic summarizing FDA data) state multiple people required medical attention and hospitalization after self‑medicating with animal ivermectin [2]. The sources do not provide a comprehensive mortality count from these human cases in the collected reporting; they emphasize hospitalization and serious adverse effects rather than detailed long‑term outcome statistics [2] [1].
4. Equine toxicity shows biologic plausibility for severe effects
Veterinary literature documents ivermectin toxicosis in horses with acute progressive neurologic signs — depression, forelimb and hindlimb ataxia, drooping lips and muscle fasciculations — with one case series reporting one horse euthanized and others recovering with supportive care; brain tissue assays in that case showed ivermectin presence, underscoring dose‑related CNS penetration and risk [4]. Drug labeling and veterinary guidance describe adverse reactions in animals and stress proper dosing, reinforcing that overdose or species‑specific sensitivity can produce severe outcomes [5] [7].
5. Balanced assessment and limits of the reporting
The documented human cases in poison‑center data and clinical summaries establish that toxicity from taking veterinary ivermectin paste has occurred and can produce severe, sometimes hospitalization‑level, illness [1] [2]. However, these sources are not population‑level epidemiology and do not provide exhaustive counts or long‑term follow‑up for all patients; likewise, while animal studies and veterinary reports demonstrate clear toxic potential in horses (including death), direct extrapolation to precise human risk thresholds is limited by differences in formulation, dosing and human pharmacokinetics [4] [9]. Agency and clinical guidance uniformly caution against human use of veterinary ivermectin and point to safer, approved human formulations and clinical pathways for treating parasitic disease or COVID‑19 [3] [2] [6].