What inactive ingredients are in veterinary (horse) ivermectin paste versus human ivermectin tablets?

1. What the comparison actually is — active ingredient versus formulation

The scientific and regulatory literature confirms the active ingredient (ivermectin) is chemically the same across human and veterinary products, but the crucial differences lie in formulation, dose strength, and route of administration rather than the active moiety itself ^{[1] [4]}. Human ivermectin is typically supplied as precisely dosed oral tablets or topical formulations designed and tested for human pharmacokinetics and safety ^{[4] [5]}, whereas veterinary ivermectin is manufactured in multiple formats — oral pastes for horses, pour‑on liquids, injectables and chewables — and often at concentrations and with excipients intended for large animals ^{[2] [1]}.

2. What is known about inactive ingredients in horse paste formulations

Publicly available consumer and pharmacy reporting identifies a variety of excipients used in veterinary ivermectin preparations; for example, one pharmacy summary names piperazine citrate and (S)‑methoprene among inactive components associated with some animal antiparasitic products ^[3]. Industry and consumer commentary also flags that veterinary pastes include solvents, carriers, flavors, and binding agents optimized for palatability and dosing in horses, and that some of those excipients are not evaluated for human safety ^{[6] [7]}. However, those sources are illustrative rather than exhaustive, and ingredient lists vary by manufacturer and specific product — the sources do not produce an authoritative, universal catalog of inactive ingredients across all horse ivermectin pastes ^{[3] [6]}.

3. What is known about inactive ingredients in human ivermectin tablets

Human ivermectin tablets (the prescription product commonly referenced in clinical use) are manufactured with excipients chosen for oral human administration and stability; official drug‑information guidance recommends asking a pharmacist for a full ingredient list for a given human product, underscoring that excipient lists are product‑specific and should be consulted when allergies or interactions are a concern ^[5]. Wikipedia and regulatory overviews describe human formulations as tablets or topical creams/lotions approved for particular parasitic indications, but the provided sources do not list standardized inactive ingredients for every human tablet brand in the dataset supplied here ^{[4] [5]}.

4. Why the inactive‑ingredient difference matters — toxicity, dosing and legal/regulatory context

Medical and veterinary experts warn that inactive ingredients in animal formulations may be unsafe in humans and that livestock products are dosed for much larger bodyweights, creating overdose risk if human consumers use veterinary paste instead of a human prescription ^{[2] [1]}. Public health advisories note poisoning reports and adverse events from accidental or intentional ingestion of veterinary products and emphasize that veterinary excipients and solvents have not been evaluated under human drug‑approval standards ^{[8] [2]}. Consumer‑oriented commentary likewise highlights that veterinary products lack the regulatory safety net and labeling intended for human use — a practical risk and legal blind spot if adverse reactions occur ^{[7] [6]}.

5. Conclusion and reporting limits

Reporting across consumer health sites, pharmacy summaries and academic reviews converges on three points: the active ivermectin molecule is the same across human and animal products, formulations (including inactive ingredients) differ and can pose human safety risks, and specific excipient lists depend on the manufacturer and product and therefore require consulting product labels or a pharmacist for definitive answers ^{[1] [2] [5]}. The sources supplied name some veterinary additives (for example piperazine citrate and (S)‑methoprene in one pharmacy summary) and broadly document the concern about unvetted excipients, but do not provide a comprehensive side‑by‑side ingredient table for every horse paste and every human tablet — that level of specificity requires directly reading product labels or manufacturer data sheets beyond the material provided here ^{[3] [6] [5]}.