Fact check: What is the recommended dosage of ivermectin for humans vs horses?

1. Why the horse dose is repeated and what it means in practice — clear consensus on 200 µg/kg

Multiple equine-focused studies converge on the figure 200 µg/kg (0.2 mg/kg) given orally for horses and closely related equids. Researchers administering ivermectin paste in equine populations reported this dose as both effective against common nematodes and safe under study conditions, with pharmacokinetic profiles consistent with expected systemic exposure in horses ^{[1] [2] [3] [4]}. The repeated use of this numeric dose across independent equine studies constitutes a consensus within the sampled literature and is appropriate for veterinary guidance specific to horses and similar species, not for other species.

2. Evidence from mules and pharmacokinetics — intermediate findings that reinforce species-specific dosing

A study explicitly evaluated ivermectin paste at the horse dosage in mules and found both efficacy and a pharmacokinetic profile intermediate between horses and donkeys, supporting the safety of using the horse-recommended 200 µg/kg dose in mules under researched conditions ^{[1] [4]}. This demonstrates that even among equids, pharmacokinetics vary by species, and validated dosing comes from species-specific studies. The mule data strengthen the equine dosing claim but simultaneously illustrate why direct cross-species dose transfers—especially to humans—are scientifically inappropriate without targeted human pharmacokinetic and safety data.

3. The missing human dosage — an explicit omission across sources and why it matters

All documents reviewed either omit a recommended human dosage or emphasize the absence of human dosing guidance ^{[2] [3] [4]}. This consistent omission is significant: animal dosing cannot be presumed safe or effective in humans because absorption, distribution, metabolism, elimination, and safety thresholds differ between species. The literature’s silence on human recommendations functions as an implicit warning against extrapolation and points to the need for clinical pharmacology data and regulatory guidance before any human dosing claim can be supported.

4. Extra-label use in horses and the danger of under-dosing — a veterinary caution with broader implications

One analysis raises concerns about extra-label use in horses and the danger of under-dosing, which can drive resistance in parasites and compromise animal health ^[2]. That critique of dosing practices in veterinary medicine highlights a broader principle applicable across species: incorrect dosing—either too low or too high—has medical and ecological consequences, including reduced efficacy, adverse events, and selection pressure for resistance. The emphasis on careful, species-specific dosing in veterinary sources underscores why human dosing must rely on human studies and regulatory approval.

5. Agreement and limits across sources — where the literature aligns and where it stops

The sources uniformly agree on the numeric equine dose and its observed efficacy in horses and mules, but they uniformly stop short of offering human dosing guidance ^{[1] [2] [3] [4]}. That pattern indicates strong intra-domain consensus (equine veterinary use) and a clear inter-domain gap (human clinical dosing). The literature’s focus on horses and related equids, rather than humans, likely reflects study designs, ethical constraints, and regulatory frameworks that separate veterinary pharmacology from human clinical therapeutics.

6. What’s omitted and next steps for informed guidance — research and regulatory gaps

The principal omission across the reviewed analyses is any calibrated, evidence-based human dosage recommendation and human pharmacokinetic/safety data; this is not merely absence of information but a methodological boundary that precludes safe recommendations for people ^{[2] [3] [4]}. To move from veterinary consensus to actionable human guidance requires randomized clinical trials, pharmacokinetic studies, and regulatory review in humans. Until such data exist, professional guidelines appropriately avoid endorsing cross-species dose extrapolation and caution against unsupervised use.

7. Bottom line for readers seeking a direct answer — clear veterinary guidance, no human directive

The bottom line from the reviewed material: ivermectin is recommended at 200 µg/kg orally for horses and has been used safely at that dose in mules, but the documents provide no recommended human dosage and explicitly highlight that species differences preclude direct translation ^{[1] [2] [3] [4]}. Any discussion of human dosing must rely on human clinical research and regulatory-sanctioned guidance, which the sourced materials do not supply.