Fact check: What are the common side effects of ivermectin overdose in humans?

1. Dramatic neurologic presentations dominate recent reports and poison‑center data

Recent case reports and retrospective poison-center series have repeatedly described neurotoxicity as the hallmark of ivermectin overdose in humans. Individual case studies document decreases in sensorium, restlessness, complex visual hallucinations, drowsiness, agitation, confusion, and encephalopathy; poison-center analyses similarly report altered mental status, ataxia, tremor, and seizures in patients consuming higher-than-recommended doses. These neurological findings appear across acute supratherapeutic ingestions and some chronic overuse scenarios, indicating central nervous system involvement is the common—and most urgent—clinical feature in reported human toxicity ^{[1] [2] [4]}.

2. Gastrointestinal and musculoskeletal complaints are frequent accompaniments

Beyond neurologic signs, the literature consistently notes gastrointestinal symptoms—nausea, vomiting, diarrhea—and musculoskeletal or systemic complaints such as weakness and myalgias in people with ivermectin toxicity. The Oregon Poison Center retrospective specifically cataloged GI and musculoskeletal effects alongside neurotoxicity, highlighting that many patients present with a constellation of symptoms rather than isolated findings. These non‑neurologic manifestations are common and can precede, accompany, or follow neurologic deterioration, emphasizing multisystem involvement in overdose presentations ^{[2] [4]}.

3. Formulation and dose matter: veterinary products and high doses increase severity

Analyses compare outcomes in people ingesting human versus veterinary formulations and in acute versus chronic exposure patterns, and a consistent pattern emerges: ingestion of veterinary formulations and higher cumulative doses correlates with more severe toxicity. Veterinary products often contain concentrations and excipients not intended for human use, and retrospective data show those patients developed more profound neurologic impairment and required more intensive care. This dose–formulation relationship underpins much of the variability in clinical severity seen across reports ^{[2] [4]}.

4. Case studies illustrate recovery with supportive measures but underline risk

Individual case reports describe patients with severe neurologic symptoms who improved after supportive care such as activated charcoal and medical management, with no long-term neurologic sequelae reported in several instances. These accounts demonstrate that timely clinical intervention can reverse acute toxicity, yet they also underscore that serious, alarming presentations—including hallucinations and stupor—occur in people self-medicating with supratherapeutic doses. Reliance on case reports limits generalizability, but the clinical trajectory documented is consistent across multiple published cases ^{[1] [5]}.

5. Surveillance data point to demographic patterns and rising misuse during COVID‑19

Poison-center surveillance and letters to medical journals during the COVID‑19 period document increased ivermectin use and associated toxicities, with a disproportionate number of cases in older males and in individuals taking the drug for COVID‑19 prevention or treatment. A New England Journal of Medicine communication and multiple poison‑center reports tie rising exposure calls to the pandemic period, emphasizing that behavioral and public‑health contexts—rather than pharmacology alone—contributed to observed overdose patterns. These data illuminate the social drivers behind the clinical reports ^{[3] [2]}.

6. Cross‑species veterinary reports hint at shared toxicologic themes but limited human applicability

Animal case reports describe severe neurologic and autonomic signs—ataxia, seizures, hypersalivation, blindness, labored breathing—in dogs and calves after ivermectin exposure, indicating a cross‑species propensity for neurologic toxicity at high doses. However, veterinary findings must be interpreted cautiously for humans because of species differences in susceptibility, dosing, and formulations. The veterinary literature reinforces the biological plausibility of neurotoxicity but offers limited direct evidence about typical human side‑effect frequencies or thresholds ^{[6] [7]}.

7. Synthesis: what clinicians and the public should expect from reported evidence

Synthesizing case reports, poison‑center analyses, and medical correspondence yields a consistent picture: the most common side effects of ivermectin overdose in humans are neurologic (confusion, hallucinations, ataxia, decreased consciousness), accompanied by GI symptoms and sometimes musculoskeletal complaints, with severity linked to dose and formulation. Reports since 2021–2023 document increased exposures tied to COVID‑19‑related self‑medication and show that supportive care often leads to recovery, but serious acute illness can and has occurred ^{[1] [2] [3]}.