Fact check: Are there any reported cases of ivermectin overdose in humans and what were the symptoms?

1. A cluster of clinical reports shows a recurring overdose pattern

Multiple clinical case series compiled during and after the COVID-19 pandemic documented groups of patients who developed toxicity after taking ivermectin for prevention or treatment, most often at doses above recommended human regimens or after using veterinary formulations. A 2022 clinical toxicology series described 37 cases characterized by neurotoxicity, gastrointestinal symptoms, and musculoskeletal complaints, noting higher rates of altered mental status in those using veterinary products and among older male patients ^[1]. An earlier letter to a major medical journal reported 21 exposures linked to COVID-19 use with confusion, ataxia, seizures, and gastrointestinal distress, underscoring that inappropriate dosing and self-medication drove many presentations ^[2]. These reports establish that human overdose events occurred in real-world contexts of misuse and product substitution.

2. Systematic reviews and genetics identify mechanisms and vulnerable groups

A systematic review of severe neurotoxic ivermectin cases found that neurotoxicity is not limited to classical parasitic co-infections like Loa loa; it also occurs in diverse settings and is associated with ABCB1 (P-glycoprotein) loss-of-function mutations that permit central nervous system drug penetration, offering a biological explanation for some severe presentations ^[3]. This genetic vulnerability means that standard human doses can be hazardous in a subset of people who cannot effectively exclude ivermectin from the brain. The review therefore links observed clinical syndromes to identifiable mechanistic pathways, and it highlights that host genetics and co-existing infections influence severity, a critical context often omitted from simplistic overdose discussions.

3. Veterinary formulations and dosing errors amplify risk in clinical series

Comparative analyses within case collections show that people who ingested veterinary ivermectin or substantially higher-than-prescribed doses experienced more severe central nervous system symptoms, including altered consciousness and seizures. The 2022 series explicitly reported higher severity among patients using non-prescription veterinary products versus those taking prescription human tablets, indicating that dose concentration, formulation, and lack of dosing guidance materially increased toxicity risk ^[1]. Public health surveillance during the COVID era documented surges in calls and hospital visits tied to such misuse, demonstrating that product source and dosing mistakes were primary drivers of overdose incidents rather than isolated idiosyncratic reactions.

4. Animal toxicology and experimental work show biochemical injury and possible treatments

Preclinical studies in adult rats have detailed acute ivermectin toxicity effects on brain and skin tissue, including oxidative stress, altered P-glycoprotein activity, IL-5 and dopamine perturbations, and histologic changes, and they suggest potential mitigation strategies such as flumazenil and vitamin C in animal models ^[4]. While animal data cannot be translated directly to human dosing or therapy, these experiments corroborate clinical observations of neurologic injury and point to molecular pathways that explain neurotoxicity, supporting clinical concerns about high-dose exposure and informing hypotheses for therapeutic investigation in severe human poisoning.

5. Case reports include rare fatal outcomes linked to unconventional exposures

Beyond series and reviews, singular case reports document severe and even fatal events under unusual exposure routes. A recent 2025 case described fatal transdermal ivermectin poisoning after topical application of a solution to a rash, resulting in severe cerebral edema, respiratory failure, and death, emphasizing that non-oral exposure and high local absorption can produce catastrophic outcomes ^[5]. This case expands the risk profile beyond oral ingestion and shows that clinicians and public health communicators must consider formulation, route, and self-treatment behaviors when assessing ivermectin poisoning risk.

6. Big-picture synthesis: what clinicians and the public must know now

Taken together, clinical series, systematic reviews, animal experiments, and case reports produce a consistent picture: overdose or misuse of ivermectin can cause neurotoxic syndromes, gastrointestinal upset, and in rare cases death, with risk amplified by veterinary product use, excessive dosing, genetic susceptibility, and atypical exposure routes ^{[1] [2] [3] [4] [5]}. Recent sources from 2022 through 2025 document both frequency and severity patterns and identify plausible mechanistic explanations, offering a robust evidence base for public health messages that discourage self-medication and for clinical protocols prioritizing neurologic monitoring and supportive care in suspected overdose ^{[1] [5]}.