What harms and adverse‑event reports have been linked to human use of veterinary ivermectin products?
Executive summary
Use of veterinary ivermectin formulations in humans has been repeatedly linked to overdoses and a spectrum of adverse events—most commonly gastrointestinal symptoms and neurologic problems—and has produced increased poison‑control calls, emergency visits, hospitalizations and rare deaths during the COVID‑19 era [1] [2] [3]. Serious cases include ICU admissions and a documented instance of severe neurotoxicity after intravenous administration of a veterinary product, underscoring both dose‑ and route‑related danger [4] [5].
1. Scope of the reports: poison‑center, hospital and surveillance data
Federal surveillance captured a marked surge in human exposures to ivermectin coinciding with COVID‑19 interest: poison control center calls rose multiple‑fold in 2021 versus baseline and retail ivermectin dispensing also climbed, with subsequent reports of severe illness prompting CDC and FDA health alerts [2] [6] [7]. Multi‑center pharmacovigilance projects and regional poison‑center reviews documented dozens of adverse‑event cases linked to ivermectin taken for COVID‑19, including 40 cases reported to the FACT network and 37 cases described in an Oregon series, many resulting in ED visits or hospitalization [8] [3].
2. The clinical picture: gastrointestinal, cardiovascular, hepatic, dermatologic and neurologic harms
Regulatory and clinical reports list a consistent constellation of harms from inappropriate ivermectin use: nausea, vomiting, diarrhea, hypotension, allergic reactions such as itching and hives, skin rash and swelling, liver injury, and a range of neurologic adverse events including dizziness, ataxia, confusion, seizures, coma and death in extreme cases [1] [9] [10]. Surveillance analyses emphasize neurologic dysfunction in many toxicity presentations, especially among patients who ingested higher‑than‑recommended doses or animal formulations [8] [3].
3. Severity, outcomes and illustrative case reports
Most surveillance cases required emergency evaluation and a substantial proportion were hospitalized; the Oregon retrospective found 21 of 37 patients hospitalized and one death, while the FACT pharmacovigilance report showed many ED visits and admissions among its 40 cases [3] [8]. A striking clinical example is a published case of intravenous administration of a veterinary ivermectin product to a COVID‑19 patient that produced severe neurotoxicity with toxic serum levels and ICU care, demonstrating that non‑oral routes and veterinary formulations can produce unprecedented toxicity [4] [5].
4. Why veterinary formulations heighten risk: concentration, excipients and untested routes
Regulators warn that veterinary ivermectin products are often formulated at much higher concentrations for large animals and may contain inactive ingredients not evaluated for human safety; these factors, plus misuse of non‑oral routes (e.g., injectable or “pour‑on” forms) and massive single or repeated dosing, explain why animal products are particularly hazardous when consumed by people [11] [6] [12]. FDA and CVM communications explicitly advise against substituting animal ivermectin for human therapy and urge veterinarians and retailers to warn consumers, noting spikes in misuse and associated adverse events reported to poison control [7] [11].
5. Context, interpretation, biases and limitations of the evidence
The body of evidence is dominated by surveillance reports, case series and individual case reports rather than randomized controlled trials of veterinary product use in people; regulators stress there is no authorization for ivermectin to treat COVID‑19 and that safety/efficacy data for such uses are lacking [7] [13]. Sources used here—the FDA, CDC, academic case reports and poison‑center analyses—carry implicit public‑health and regulatory agendas to prioritize safety warnings, while clinicians and researchers also caution against off‑label experimentation; nevertheless, surveillance data consistently link misuse of veterinary formulations and high dosing to the harms described, even if exact incidence and causal attribution are limited by underreporting and heterogeneous documentation [2] [8] [13].