How do veterinary ivermectin doses for cattle, horses, and dogs compare to human doses on a mg/kg basis?
Executive summary
On a mg/kg basis, typical veterinary ivermectin doses for cattle and horses are about 0.2 mg/kg (200 µg/kg) as a single treatment, while common human therapeutic dosing is about 0.15–0.2 mg/kg (150–200 µg/kg) as a single dose for parasitic infections; some veterinary labels and manuals show 0.1–0.2 mg/kg for livestock and 0.2 mg/kg for horses, and human guidance commonly cites 150–200 µg/kg [1] [2] [3] [4]. Coverage in the provided sources is consistent on those typical per‑kg ranges but does not address every product variation, formulations, or repeat‑dosing regimens [5] [6].
1. What the labels and vet manuals say: livestock and horses
Regulatory product information and veterinary manuals commonly list ivermectin doses for cattle and horses around 0.1–0.2 mg/kg: Merck’s MSD Veterinary Manual and some product datasheets show 0.2 mg/kg for cattle (single subcutaneous injection for lice/Psoroptes) and 0.2 mg/kg PO for horses [1] [2]. Other technical summaries note that agricultural single doses have been recommended at around 0.1 mg/kg in some settings, emphasizing low mg/kg values compared with misperceptions of “very high” livestock dosing [7].
2. Typical human therapeutic dosing (mg/kg)
Human prescribing references list ivermectin dosing around 150–200 µg/kg (0.15–0.2 mg/kg) as the usual single oral dose for conditions such as onchocerciasis or strongyloidiasis — for example, the Mayo Clinic cites 200 µg/kg as a standard single dose in adults and children ≥15 kg [4]. A pharmacokinetics review also documents human dosing in the 150 µg/kg range in clinical use for onchocerciasis [3].
3. Direct comparisons: livestock vs. human on a mg/kg basis
On a straight mg/kg comparison, the commonly labeled veterinary doses for cattle and horses (≈0.1–0.2 mg/kg) overlap with human therapeutic mg/kg doses (≈0.15–0.2 mg/kg). Product examples show cattle and swine injectables containing 10 mg/mL and dosing guidelines like 1 mL per 110 lb (~50 kg → ~0.2 mg/kg), which aligns with the 200 µg/kg figure [8] [2]. Thus, the numerical mg/kg dose is not always dramatically higher in veterinary products than in human prescriptions [8] [2] [4].
4. Why formulations and safety matter: more than mg/kg
Available sources emphasize that active ivermectin is the same molecule across formulations but formulations differ (tablets, horse paste, cattle injectable), and those differences—concentration, excipients, route (oral vs. subcutaneous), intended single use, and dosing frequency—affect safety and appropriateness for species [9]. The University of Illinois news piece warns against using animal formulations meant for other species because of formulation differences and cumulative dosing risks [9].
5. Toxicity, species sensitivity, and misuse risks
Vet literature and reviews note species‑specific sensitivities (notably certain dog breeds such as collies) and higher dose thresholds for toxicosis; documented toxic doses in animals are often substantially above labeled therapeutic mg/kg (for example, ataxia or CNS signs in horses at ~2 mg/kg and cattle at higher multiples), but misuse (wrong dilution, repeated dosing) has caused poisonings in people who took animal products [1] [7] [9]. Sources stress that “at least 10 times the normal dose” may be needed for toxic reactions in some species, but breed/genetic vulnerabilities alter risk [1] [7].
6. What the sources do not say / limitations
Provided sources do not comprehensively list every veterinary product’s mg/kg recommendations (product‑to‑product variability exists) nor do they present pharmacokinetic comparisons (Cmax, bioavailability) between animal injectable/paste forms and human tablets for the same mg/kg dose; those kinetic differences can change clinical effects and are not detailed in these search results (not found in current reporting). Also, none of the cited documents endorse humans using animal formulations; in fact, warnings against that practice appear [9] [8].
7. Practical takeaway and competing messages
Numerically, typical labeled veterinary doses for cattle and horses (≈0.1–0.2 mg/kg) are in the same mg/kg band as standard human therapeutic doses (≈0.15–0.2 mg/kg) according to the materials provided [1] [2] [3] [4]. However, veterinary formulations, concentrations, routes, species‑specific instructions, and safety warnings mean labeled animal products are not interchangeable with human prescriptions; veterinary materials and public‑facing reporting explicitly warn against people taking livestock products due to formulation and dosing risks [9] [8].