What doses of veterinary ivermectin are considered toxic in adults and children compared to approved human ivermectin dosing?
Executive summary
Approved human oral ivermectin is typically dosed by weight at about 150–200 micrograms per kilogram (µg/kg) as a single dose for most parasitic indications; tablets are sold as 3 mg units [1] [2]. Reports of toxicity from people taking veterinary formulations list ingested amounts ranging from a few milligrams up to >100 mg of paste or solutions, and case series link such misuse to confusion, ataxia, seizures, and hypotension (reported veterinary-product ingestions 6.8–125 mg of 1.87% paste and 20–50 mg of 1% solution) [3].
1. What the approved human doses are — the baseline
Human oral ivermectin dosing is weight-based, commonly 150–200 µg/kg as a single dose for infections such as strongyloidiasis and onchocerciasis; tablets come in 3 mg strengths and dosing must be determined by a clinician based on body weight [1] [2]. Mass-treatment regimens in some programs have used higher single annual doses — for example 0.4 mg/kg once yearly in filariasis campaigns — but those are programmatic regimens under medical supervision [4].
2. How veterinary products differ and why that matters
Veterinary ivermectin formulations (pastes, solutions, injectables) are manufactured at concentrations and in dose volumes intended for large animals; users who take these products orally may ingest many times the mg quantity intended for a human. Case reports collected by clinicians show people ingesting veterinary paste or solutions that delivered from roughly 6.8 mg up to 125 mg of ivermectin in single episodes — far above typical human single doses of a few milligrams for a 60–80 kg adult [3].
3. Numbers to compare: “approved” vs. reported toxic ingestions
A 70-kg adult receiving 200 µg/kg would get 14 mg (70 kg × 0.2 mg/kg); commonly available 3 mg tablets mean roughly 4–5 tablets [1] [2]. Case reports of veterinary-product ingestion include amounts of 20–125 mg — two to ten times (or more) the human therapeutic single dose — and these higher ingestions were associated with hospitalizations and serious neurologic effects [3].
4. What is known about toxicity thresholds in adults
Controlled human trials have administered doses higher than standard and found tolerability up to certain limits: a dose-escalation trial in healthy adults reported no clear CNS toxicity for doses up to roughly 10 times the highest FDA‑approved single dose (study arms included single doses up to 90–120 mg in small cohorts) and generally acceptable tolerability, but real-world overdoses and veterinary-product misuse have still caused severe events [5]. The clinical case series emphasize that neurologic toxicity (confusion, ataxia, seizures) and cardiovascular effects have occurred with inappropriate use of veterinary products [3].
5. Children: dosing complexity and exposure differences
Regulatory guidance and trials typically limit tablet use to children weighing ≥15 kg, with pediatric dosing the same weight-based (150–200 µg/kg) approach as adults [1] [2]. Pharmacokinetic studies show children clear ivermectin faster and have roughly half the exposure (AUC/Cmax) compared with adults on the same µg/kg dose, leading researchers to model higher pediatric doses (e.g., ~250–300 µg/kg) or height-based dosing to achieve similar exposure — but those are research findings informing dosing strategy, not universal approvals [6] [7] [8].
6. What counts as “toxic” in children — evidence gaps
Available sources do not establish a precise mg/kg toxicity cutoff for children ingesting veterinary products; clinical pharmacology papers document lower exposure at equivalent mg/kg doses and propose adjusted dosing to match adult exposure, but case reports of poisoning largely describe adult misuse of veterinary forms [6] [8] [3]. Therefore, explicit pediatric toxicity thresholds from veterinary-product ingestion are not reported in the available sources.
7. Practical takeaways and limitations of the record
In short: approved human single doses are about 150–200 µg/kg (tablets 3 mg each) [1] [2]; veterinary-product ingestions reported in clinical series delivered tens to hundreds of milligrams and are linked to severe toxicity [3]. Controlled trials show higher-than-standard doses can be tolerated in small, supervised adult cohorts [5]. Limitations: published pharmacokinetic work shows children differ from adults and researchers have proposed higher pediatric doses to match exposures, but these are research conclusions rather than universal clinical practice changes [6] [7]. Available sources do not provide a single mg/kg “toxic” threshold for children from veterinary formulations.
If you want, I can convert the weight-based human doses into tablet counts for specific adult and child weights, and summarize the veterinary-product reported ingestion ranges alongside the corresponding fold-increase over therapeutic human dosing.