What are typical ivermectin doses (mg/kg) for common veterinary species versus humans?
Executive summary
Typical human therapeutic ivermectin doses used for parasitic infections are about 150–200 micrograms per kilogram (mcg/kg) as a single oral dose; higher investigational human regimens have tested up to 2,000 mcg/kg in trials (200–800 mcg/kg have been used in some onchocerciasis and malaria studies) [1] [2]. Veterinary dosing varies by species and product: common labeled doses for cattle and horses are about 0.2 mg/kg (200 mcg/kg) (subcutaneous or oral depending on species), while toxicity in dogs is reported at much higher levels (signs often at >2 mg/kg) and some veterinary uses involve concentrated injectable or paste formulations that are not interchangeable with human tablets [3] [4] [5].
1. Humans: the standard, approved range and experimental escalation
For routine, approved human indications (onchocerciasis, lymphatic filariasis, strongyloidiasis), clinicians prescribe ivermectin by body weight at roughly 150–200 mcg/kg as a single oral dose; product information and major clinical references state 200 mcg/kg as the usual single dose for adults and children ≥15 kg [1] [2]. Researchers have tested higher human doses in controlled trials: single doses as high as 800 mcg/kg have been used for onchocerciasis and dose-finding studies for malaria transmission reduction have evaluated repeated regimens up to several hundred mcg/kg per day and noted tolerability even with escalations up to 2,000 mcg/kg in investigational settings [2].
2. Veterinary practice: species, route, and common mg/kg numbers
Veterinary ivermectin dosing is species-specific and depends on formulation and route. For cattle and horses, a commonly cited effective dose is 0.2 mg/kg (that is, 200 mcg/kg) administered subcutaneously in cattle or orally in horses as part of parasite control programs [3]. Veterinary products come as injectables, drenches, and concentrated pastes; these forms and concentrations differ markedly from human tablets and are approved under separate regulatory frameworks [3] [5].
3. Safety margins, toxicity thresholds and breed vulnerabilities
Ivermectin has a wide therapeutic index overall, but toxicity emerges when doses far exceed therapeutic ranges or when veterinary routes (e.g., parenteral) or formulations are misused in humans. Reports and reviews indicate neurologic toxicity in humans after very high exposures or non-oral administration of veterinary products; one case report linked combined high oral dosing (>0.4 mg/kg/day) plus an intravenous veterinary bolus to neurotoxicity [6]. In dogs, clinical signs of toxicosis are commonly reported at doses greater than about 2 mg/kg, and certain breeds with MDR1 gene mutations (Collies, Shetlands and related crosses) are uniquely susceptible to neurotoxicity even at much lower doses [3] [4].
4. Why mg/kg units vary in headlines and what to watch for
Confusion arises because veterinary literature often quotes mg/kg (0.2 mg/kg = 200 mcg/kg) while human medicine typically states mcg/kg (150–200 mcg/kg). Also, veterinary formulations are sometimes concentrated for large animals (horses/cattle), so the same product volume can deliver much higher mg/kg doses if given to a small animal or person. Public health reporting and poison control alerts repeatedly emphasize that the active ingredient is identical but formulations, concentrations and routes differ — making direct cross-use dangerous [5] [7].
5. Competing perspectives in the sources: approved use vs experimental interest
Regulatory and clinical sources focus on approved antiparasitic uses at standard single doses of 150–200 mcg/kg in humans [1]. Research groups explore higher or repeated dosing for public-health goals (malaria transmission reduction, higher-dose onchocerciasis trials) and report tolerability in controlled settings up to several-fold higher than standard human doses — but those are investigational and monitored closely [2]. News and veterinary experts warn against repurposing concentrated animal products for human use because formulation and route differences have caused poisonings and neurotoxicity [7] [6].
6. Practical takeaways and limitations of available reporting
Do not substitute veterinary ivermectin products for human prescriptions; labeled human dosing is weight-based at about 150–200 mcg/kg [1], and veterinary products can deliver much higher mg/kg amounts and are formulated for different routes [5]. Available sources document investigational human dosing up to 2,000 mcg/kg in trials [2] and case reports of toxicity when veterinary products or non-oral routes were used in people [6]. Sources provided do not offer a comprehensive species-by-species veterinary dosing table for every common companion or farm animal dose beyond the cited examples; a full dosing reference requires product labels or veterinary formularies (available sources do not mention a complete cross-species dosing chart).
If you want, I can extract a concise mg/kg comparison table for specific species you care about (humans, dogs, cats, horses, cattle, sheep/goats) using only the sources above and flag where product-specific labels or breed cautions apply.