What is ivermectin and how does veterinary ivermectin differ from human formulations?

1. What ivermectin is and how it works

Ivermectin is a macrocyclic lactone derived from Streptomyces avermitilis with broad antiparasitic activity against both ecto‑ and endoparasites, which led to its widespread use in veterinary practice and specific approved human uses such as treatment of onchocerciasis and intestinal strongyloidiasis as well as topical use for lice and rosacea ^{[1] [6]}.

2. Human formulations and regulatory context

Human‑approved ivermectin is made and tested as precise oral tablets or topical formulations with defined dosing regimens and safety data for human indications; these formulations have been evaluated through regulatory pathways for efficacy and safety in humans and are not approved for COVID‑19 treatment or prevention ^{[6] [3]}.

3. Veterinary formulations: variety, concentration and intended use

Veterinary ivermectin comes in many forms tailored for animals — concentrate injectables, oral drenches, pastes (notably equine pastes), and pour‑on solutions for livestock — designed for different species, routes and larger body masses, and therefore often at much higher concentrations and with different excipients or vehicles than human products ^{[2] [3] [7]}.

4. How formulations change pharmacokinetics and risk

Different vehicles and routes of administration used in veterinary products alter ivermectin pharmacokinetics — subcutaneous or long‑acting depot injections used in animals yield different absorption and elimination profiles than human oral or topical forms, and modifying the vehicle can substantially change bioavailability and tissue exposure, which affects safety and efficacy ^{[1] [8] [9]}.

5. Safety, toxicity and documented harms from misuse

Public‑health agencies and poison‑control data documented a surge in human exposures and toxicity during the pandemic when people ingested veterinary or non‑prescribed human ivermectin; clinical series report hospitalizations, neurologic symptoms and at least one death among cases of overdose, and veterinary formulations intended for large animals were specifically implicated as highly concentrated products that produced severe adverse events in humans ^{[5] [10] [3]}.

6. Why veterinary products are unsafe substitutes for human medicines

Even when the active molecule is the same, animal drugs have not been evaluated for human safety or effectiveness, may contain different inactive ingredients or preservatives, and may be formulated at dosages appropriate for horses or cattle rather than people — factors regulators cite when warning against treating human medical conditions with veterinary ivermectin ^{[3] [6] [11]}.

7. Market effects and broader consequences

Demand spikes for ivermectin tied to misinformation increased prices and strained supplies, with one analysis showing veterinary product prices rising dramatically during 2021 and commentators noting both price discrimination and that veterinary products sometimes face less stringent distribution channels — consequences that affected access for animals and created public‑health risks ^[4].

8. Bottom line

The active compound ivermectin is shared between human and veterinary medicines, but formulations, concentrations, approved uses, pharmacokinetics, safety testing and intended routes differ materially; regulators and clinical toxicologists therefore uniformly advise using only appropriately prescribed human formulations for human illnesses and avoiding veterinary products, which have caused documented poisonings when misused ^{[6] [3] [10]}.