What clinical cases exist where veterinary ivermectin was used to treat humans, and what were the outcomes?
Executive summary
Reports and case-series show multiple instances where people ingested veterinary ivermectin formulations — most commonly during the COVID-19 pandemic — producing a spectrum of outcomes from mild gastrointestinal complaints to severe neurotoxicity and at least one reported death in a reviewed cohort [1] [2]. Scattered clinical-use reports exist where veterinary (parenteral) ivermectin was given orally in human parasitic disease trials with generally favorable parasitologic outcomes but occasional serious reactions, and a single published case documents intravenous veterinary ivermectin causing severe, non‑fatal encephalopathy [3] [4].
1. Documented poison‑center and emergency‑room cases: who took veterinary ivermectin and what happened
A retrospective review from an Oregon poison center identified 37 ivermectin toxicity cases tied to prevention or treatment of COVID‑19; 17 of those involved veterinary formulations, most patients were older males, many required hospitalization, and clinical effects centered on neurotoxicity (30 cases), gastrointestinal symptoms , and musculoskeletal complaints , with one death reported in the series [1]. The New England Journal of Medicine summarized 21 patients who had taken ivermectin for COVID‑19 prevention or treatment and reported that six of those were hospitalized for toxic effects; several of the exposures involved veterinary pastes or solutions with highly variable doses (reported veterinary doses ranged widely, e.g., 6.8 mg to 125 mg paste and 20–50 mg solutions) [2].
2. Severe and unusual individual clinical reports: intravenous use and encephalopathy
A unique case report describes a patient who received intravenous veterinary ivermectin for COVID‑19 and developed severe neurotoxicity requiring ICU care; the authors note this is the first published report of intravenous administration of ivermectin in a human and emphasize that non‑fatal outcome here contrasts with historical fatal encephalopathy cases tied to onchocerciasis treatment, highlighting overdose and blood‑brain mechanisms as likely drivers of harm [4].
3. Controlled clinical use of veterinary formulations in parasitic disease — limited but positive signals and a notable adverse event
A randomized trial in Thailand compared a single oral dose of a parenteral veterinary ivermectin preparation (given orally) against a 7‑day high‑dose albendazole regimen for chronic strongyloidiasis and concluded ivermectin was superior; the study reported one case of acute generalized exanthematous pustulosis temporally linked to the veterinary preparation but otherwise suggested oral use of the parenteral veterinary product was effective and largely safe in that controlled setting [3].
4. Broader context: rising off‑label veterinary use, regulatory warnings, and contested efficacy for COVID‑19
The rapid surge in public interest in ivermectin during the pandemic, and consequent off‑label use of veterinary products, triggered warnings from health authorities; reviews and commentaries document increased prescriptions and poison‑center calls and note that authoritative agencies have warned against using veterinary ivermectin for COVID‑19 because randomized trials do not show convincing clinical benefit and safety is unestablished for such formulations [5] [2]. Systematic reviews and meta‑analyses of ivermectin (largely focused on human‑grade formulations) have produced mixed and often low‑certainty findings about mortality or viral outcomes, with assessments frequently flagged for high risk of bias — these debates are relevant but do not validate use of veterinary products in humans [6] [7] [8].
5. What the reporting cannot resolve and the key limitations of the evidence
Available evidence about veterinary‑formulation use in people is dominated by poison‑center series, case reports, and a few small trials repurposing parenteral products orally; these sources document real harms (neurotoxicity, hospitalizations, at least one death) and rare controlled efficacy signals in parasitic disease, but do not establish safety, dosing equivalence, or regulatory approval for veterinary products in humans — rigorous trials of veterinary preparations in humans are essentially absent and pharmacokinetic differences and formulation intent remain important unanswered questions [1] [3] [9] [5].