What ingredients differ between horse paste ivermectin and human versions?

1. The active ingredient is the same; formulation and delivery differ

Reporting from university and science outlets states that the active pharmaceutical ingredient — ivermectin — is identical across human and animal products, but the way it is formulated and delivered is different: human ivermectin is typically a swallowed tablet or an approved topical, whereas animal ivermectin is sold as pastes, injectables or pour‑ons optimized for animals ^{[1] [7]}.

2. Strength per dose and intended dose schedule diverge sharply

Veterinary pastes are concentrated and packaged to dose very large animals: a typical horse paste syringe contains enough paste to treat a 1,250–1,500 lb horse at about 200 mcg/kg, with weight markings and a plunger calibrated for equine weights ^{[2] [8]}. Human prescriptions use much smaller, specifically calculated doses. That mismatch means a syringe marked for a horse can deliver many times a typical human dose and carries significant overdose risk if used by people ^{[4] [6]}.

3. Inactive ingredients and carriers — a key difference with safety implications

Government and medical communications emphasize that inactive ingredients matter: many inactive ingredients used in animal products have not been evaluated for human safety or are included in different quantities, and can affect absorption or cause direct harm ^{[5] [2]}. Industry and clinic pieces note that animal pastes may include flavorings, oily carriers, or other excipients to aid absorption in horses — features that are unnecessary or potentially harmful for humans ^{[9] [10]}.

4. Labeling and regulatory testing: “not for use in humans” is explicit

Package inserts and databases for specific ivermectin pastes explicitly state they are formulated for horses only, have not been tested in humans, and warn against human use; regulators review both active and inactive ingredients when approving human drugs, a process not applied to animal formulations intended solely for veterinary use ^{[2] [3] [5]}.

5. Toxicity concerns: dose, accumulation, and misuse

Clinicians and scientists warn that toxicity can result from a single excessive dose or from repeated dosing that causes accumulation; ivermectin labels (human and animal) often describe intended single‑use dosing and the dangers of taking multiple doses in sequence, which some people attempting off‑label antiviral regimens have done ^{[1] [6]}. Reporting also quantifies that lethal doses are far above typical therapeutic doses, but practical risk comes from inadvertent high intake and untested excipients in animal products ^[7].

6. Areas of disagreement or uncertainty in public reporting

Some consumer or retail sources emphasize differences in carriers and flavorings and suggest specific other antiparasitic actives may be present in multi‑ingredient animal products; a retail article claimed human formulations include additional agents (praziquantel, pyrantel) in some cases — but broader reporting and regulatory notices focus on excipient and dose differences rather than asserting consistent extra active drugs across all human products ^[9]. Available sources do not give a universal, itemized list of inactive ingredients across all horse pastes versus all human ivermectin formulations; composition varies by brand and product and must be checked on specific labels (not found in current reporting).

7. Practical takeaway and reporting caveats

Public health and veterinary–medical reporting uniformly cautions: don’t use animal ivermectin on people because of concentrated dosing and untested inactive ingredients; read product labels and seek human‑grade prescriptions when ivermectin is medically indicated ^{[5] [6] [4]}. Limitations: the supplied sources document broad categories of difference (dose, excipients, form, labeling) but do not provide a complete, side‑by‑side ingredient table for every brand — for precise comparisons refer to the specific product’s label or DailyMed entry ^{[2] [3]}.