Have there been reported adverse events from people using horse paste ivermectin instead of prescribed human ivermectin?

1. Reported harms and their scale

Multiple clinical reports and poison-center analyses recorded dozens of ivermectin toxicity cases tied to misuse for COVID‑19: a retrospective poison-center review identified 37 cases that resulted in healthcare visits, with most patients hospitalized and one death reported ^[2], while a New England Journal of Medicine letter noted that six of 21 people in a case series required hospitalization for toxic effects, some after taking veterinary formulations ^[1]. Poison-control summaries and hospital case reports describe severe presentations from ingesting veterinary paste or concentrated solutions, including gastrointestinal collapse, neurologic symptoms (confusion, seizures, loss of consciousness), hypotension and other life‑threatening effects ^{[3] [4] [5]}.

2. What made veterinary products dangerous for humans

Veterinary ivermectin pastes are formulated and dosed for large animals and can contain much higher concentrations than human tablets; using these products led some people to ingest single very large doses or repeated high daily doses, producing overdoses that exceed human therapeutic ranges ^{[1] [2] [6]}. Manufacturer warnings for horse pastes explicitly say “Not for use in humans” and advise reporting adverse events to animal‑drug channels, underscoring that these products were never intended for human consumption ^{[7] [6] [8]}.

3. Types of toxicity and plausible mechanisms

Clinical and pharmacovigilance literature links ivermectin toxicity to neurologic adverse events — dizziness, confusion, seizures, coma — and to drug–drug interactions or conditions that impair the blood–brain barrier; case series and reviews note that concomitant medications that affect CYP3A4 or P‑glycoprotein transport can raise central nervous system exposure and may explain some severe events ^[9]. Reports also connect overdose patterns (very large single doses or repeated high dosing) to rapid onset systemic toxicity described in emergency departments ^{[2] [3]}.

4. Public‑health signals and surveillance data

Poison‑control centers and public agencies documented a marked uptick in human exposures to ivermectin during the pandemic, often tied to veterinary products found in agricultural households or purchased at livestock supply stores; public advisories from CDC and FDA warned that adverse‑effect reports increased substantially compared with pre‑pandemic baselines ^{[10] [4]}. Media fact‑checks and health system warnings emphasized that social‑media claims about quick cures encouraged risky self‑medication and strained emergency services ^{[5] [10]}.

5. Counterpoints, approved uses, and research context

Ivermectin is an FDA‑approved human medicine for specific parasitic infections and is typically safe at approved doses under clinical supervision, but randomized controlled trials have not demonstrated efficacy for COVID‑19 prevention or treatment and in vitro antiviral effects would require far higher doses than human regimens provide ^{[1] [4]}. Some individuals who experienced toxicity had obtained human‑formulation ivermectin by prescription, indicating that even human preparations can produce harm if dosed inappropriately ^[1], while researchers caution that some rare serious neurological events have complex causes (underlying disease, drug interactions, genetic variants) beyond simple overdose ^[9].

6. What the reporting suggests about motives and misinformation

Reporting shows a mix of drivers: desperation for COVID‑19 treatments, amplification by social media and influencers, and availability of veterinary supplies in farming communities created an ecosystem where dangerous self‑dosing spread ^{[10] [5]}. Clinical and regulatory sources (NEJM, poison centers, FDA/CDC summaries) aimed to correct misinformation and reduce harm, while some community narratives and advocacy for off‑label use downplayed risks; readers should weigh clinical surveillance data and manufacturer warnings more heavily than anecdotal social‑media claims ^{[1] [7] [5]}.