How do veterinary ivermectin formulations and concentrations (pour-on, injectable, oral paste) differ from human formulations in mg/mL and mg/g?
Executive summary
Veterinary ivermectin products commonly contain far higher nominal concentrations than human formulations: livestock injectables are sold as 1% (10 mg/mL) and concentrated long‑acting preparations as about 3.15% (31.5 mg/mL), while animal “paste” and pour‑on forms are formulated and dosed for large animals rather than people [1] [2] [3]. Human ivermectin is available in regulated tablet and topical forms approved at specific therapeutic doses, and the FDA cautions that animal formulations differ chemically and in their vehicles, with safety in humans untested [3] [4].
1. Veterinary injectable concentrations — concentrated and long‑acting
Commercial veterinary injectable ivermectin preparations include standard injectables labeled as 1% ivermectin (which equals 10 mg of ivermectin per mL) and more concentrated long‑acting formulations around 3.15% (≈31.5 mg/mL); these higher percentages are deliberate pharmaceutical choices to extend persistence of drug in tissues and circulation for parasite control in livestock [1] [2]. Studies of long‑acting veterinary formulations report extended tissue residence and variable plasma half‑lives in animals depending on the vehicle, reflecting that the percent concentration and the formulation vehicle together determine how long therapeutically active ivermectin remains in an animal [2] [5].
2. Pour‑on formulations — topical, vehicle‑dependent, and targeted for animals
Pour‑on (topical) veterinary products are formulated to deliver ivermectin across animal skin using solvent vehicles that enhance absorption; regulatory descriptions and reviews emphasize that pour‑on, injectable, drench and paste products for animals are distinct classes with different vehicles and pharmacokinetics, and the FDA warns these are not equivalent to human topical products [3] [6]. Reporting and reviews highlight that changing the vehicle (the solvent/carrier) changes systemic availability, so two pour‑on products with the same labeled percent could produce different blood levels in treated animals [7] [6]. The sources do not supply a single universal mg/mL figure for all pour‑on products because manufacturers vary solvent systems and label concentrations by species and use [7] [6].
3. Oral paste for large animals — high delivered doses, animal‑calibrated markings
Oral paste preparations (commonly for horses) are manufactured and calibrated to deliver ivermectin doses appropriate for animals weighing hundreds of kilograms; commentary about these pastes warns they are not intended or tested for human consumption and that dose markings on tubes correspond to animal weights rather than human dosing [8] [3]. Some consumer and veterinary sources note that the percent strength and excipient mix of horse paste differs from human tablets and that using veterinary paste can deliver far larger mg/kg exposures than standard human regimens, though peer‑reviewed numeric concentrations for every paste product are not summarized across the literature provided [8] [6].
4. Human formulations — standardized tablets and topical forms, lower therapeutic doses
Human ivermectin is approved as oral tablets for specific parasitic infections and as topical formulations for lice and skin conditions; regulatory guidance stresses human products are manufactured and dosed to achieve established therapeutic exposures and have been evaluated for human safety, in contrast to animal products that use different vehicles and concentrations [3] [4]. The reviewed literature points to human plasma half‑life estimates and human pharmacokinetic reviews but does not list every tablet mg strength in the supplied sources, so precise tablet mg per tablet claims cannot be documented here from these reports [5] [4].
5. Why concentration differences matter — vehicles, dosing per kg, and safety
Higher nominal concentrations in veterinary injectables (1% and 3.15%) and animal pastes reflect dosing strategies for very large animals and use of organic solvent vehicles that alter absorption — factors that can produce much higher plasma or tissue residues in treated animals than would be achieved with a human tablet dose, and which also create unknown safety risks if animal products are used by people [1] [2] [6]. The FDA explicitly warns animal ivermectin products are different formulations than human products and have not been tested for human safety, a central regulatory and public‑health rationale for discouraging off‑label use of veterinary ivermectin by humans [3].