What are the clinical signs and timeline of severe ivermectin toxicity in adults and children?
Executive summary
Severe ivermectin toxicity in humans typically presents first with gastrointestinal symptoms (nausea, vomiting, abdominal pain, diarrhea) and early neurologic signs (dizziness, blurred vision, confusion, ataxia), then may progress over hours to days to hypotension, seizures, coma and rarely death; U.S. public-health alerts and case series record hospitalizations with confusion, ataxia, hypotension and seizures (CDC/FDA/NEJM reporting) [1] [2] [3]. Children and small patients are excluded from some mass campaigns because safety below 15 kg is not established; pediatric case reports show neurotoxicity can occur at high ingestions and require supportive care, sometimes intensive care [4] [5] [6].
1. Early signs: gastrointestinal upset and subtle neurologic changes
Clinical series and public-health advisories list nausea, vomiting, abdominal pain and diarrhea as the common first features of ivermectin overdose, often accompanied by headache, blurred vision, dizziness and mild confusion; poison-control case clusters in the pandemic showed most non-hospitalized cases had gastrointestinal distress and vision symptoms [1] [2] [3].
2. Neurologic progression: ataxia, confusion, seizures and coma
When toxicity advances the dominant picture is central nervous system depression — ataxia (loss of coordination), marked confusion, tremor and seizures — reflecting ivermectin’s ability at high concentrations to affect GABA-mediated CNS transmission; reports include ICU admissions for ataxia, seizures and severe confusion, and federal warnings list seizures and coma among possible outcomes [2] [1] [7].
3. Cardiovascular and respiratory deterioration: hypotension and respiratory depression
Case reports and the FDA advisory describe progression to hypotension (low blood pressure) and, in severe cases, respiratory depression requiring supportive measures; CDC and state advisories specifically list fast heart rate and low blood pressure among symptoms that should prompt immediate medical attention [1] [3] [8].
4. Timing: hours to days, with variability by dose and formulation
Available reporting shows symptoms can appear within hours after ingestion and may worsen over the following day; severity depends on total dose, formulation (veterinary products can be far more concentrated) and repeated dosing — cumulative exposures over days cause higher risk — and some cases have required days to weeks of supportive care [9] [10] [11].
5. Children: smaller margins, documented pediatric poisonings
Children under 15 kg are typically excluded from standard mass-administration programs because safety isn’t established; pediatric case reports document severe neurotoxicity after large accidental ingestions (examples include young children given very high mg/kg doses) and successful management has relied on aggressive supportive care because no specific antidote exists [4] [5] [6].
6. Formulation and source matter: veterinary products amplify risk
Many severe poisonings arose from people taking veterinary ivermectin (horse and livestock formulations) that contain much higher concentrations and inactive ingredients not intended for humans; poison-center surges reported during COVID-19 correlated with misuse of animal products and over-the-counter access has been implicated in increased exposures [9] [10] [3].
7. Management: supportive care only; no specific antidote
Guidance across reviews and case reports emphasizes that there is no antidote for ivermectin; clinicians treat symptoms — airway, breathing, circulation support, antiseizure measures and monitoring — and recovery can take days to weeks depending on dose and complications [12] [13] [7]. Some veterinary literature describes experimental measures (e.g., lipid emulsion) for animals, but human-specific antidotes are not described in current reporting [14].
8. Frequency and public-health context: rising poison-center calls during COVID era
Multiple public-health sources documented sharp increases in ivermectin prescriptions and poison-control calls during the COVID-19 pandemic; CDC and FDA issued advisories after clusters of severe illness, and the NEJM case series described hospital and ICU admissions linked to inappropriate use [11] [2] [9].
9. Limitations and disagreements in the record
Published sources agree on symptom clusters and that toxicity is dose- and source-dependent, but available material lacks a single prospective timeline stratified by precise ingested mg/kg for children versus adults; randomized-trial literature focuses on efficacy, not overdose kinetics, and veterinary reports provide mechanism but are not directly transferable to humans [15] [14] [16]. Available sources do not mention a validated pediatric antidote or precise mg/kg thresholds for predictable CNS catastrophe in humans.
10. Practical takeaway — when to seek urgent care
Seek emergency care or call poison control immediately for any unprescribed ivermectin ingestion, especially if gastrointestinal symptoms combine with neurologic signs (blurred vision, confusion, ataxia, seizures) or if a veterinary product was used; public-health advisories and the FDA explicitly advise against self-treatment and emphasize supportive management in hospitals for severe cases [1] [3] [2].
If you want, I can extract the specific symptom lists and case counts from the NEJM, FDA and CDC pieces cited here, or assemble a brief checklist you could use for triage or patient counseling (sources above).