What are standard veterinary ivermectin dosing ranges for dogs, cats, horses, and cattle by weight?
Executive summary
Veterinary ivermectin dosing commonly centers on a standard of roughly 0.2 mg/kg (200 mcg/kg) for large animals such as cattle and horses, and much lower, weight‑based monthly preventive doses for dogs and cats (for example, ~50–70 mcg/kg monthly for canine heartworm prevention in many products) — but therapeutic and off‑label regimens vary widely and carry toxicity risk in sensitive breeds (MDR1) [1] [2] [3] [4]. Official cattle injectable labels and veterinary formularies typically state 200 mcg/kg (0.2 mg/kg) as the recommended dose for many indications; small‑animal uses require exact product guidance because therapeutic doses for mites or demodicosis are often orders of magnitude higher than heartworm preventive doses and need veterinary oversight [5] [1] [6].
1. Standard large‑animal benchmarks: the 0.2 mg/kg anchor
Veterinary labels and manuals for livestock and horses converge on roughly 0.2 mg ivermectin per kg body weight (200 mcg/kg) as the routine single dose for many parasitic indications: for cattle this is the labeled subcutaneous injection rate for common worms, grubs and mites, and many horse parasite programs reference 0.2 mg/kg as a standard oral dose repeated as needed for control of gastrointestinal worms and microfilariae [5] [1]. Parasitipedia and technical datasheets echo the same 200 mcg/kg figure as the usual therapeutic dose used worldwide and note residue and approval constraints in dairy animals [7] [8].
2. Horses: product forms and usual dosing guidance
Horses are commonly treated with ivermectin at about 0.2 mg/kg orally; manufacturers and veterinary manuals state this dose kills many nematodes and microfilariae though it does not affect some adult filarial parasites, and repeat treatments are part of parasite control programs [1] [2]. Horse paste products are formulated to deliver that mg/kg amount per syringe [2]. Injectable formulations intended for cattle/swine are not generally used in horses, and product selection matters [7] [2].
3. Cattle and swine: the labeled injectable rate and practical dosing
Commercial ivermectin injectable products for cattle and swine are formulated and labeled to deliver 200 mcg/kg (0.2 mg/kg), with administration instructions such as 1 mL per 110 lb (50 kg) corresponding to that dose; the Dailymed product insert explicitly frames 200 mcg/kg as the recommended cattle dose for many parasites [5]. Parasitipedia and MSD Vet Manual confirm the same dosing benchmark and warn about residue withholding periods for lactating animals [7] [1].
4. Dogs and cats: low‑dose prevention vs. higher therapeutic regimens
For small animals there are two very different regimes: heartworm prevention uses very low, monthly doses tailored by product (for example Heartgard dosages translate to tens of micrograms per kilogram per month), while treatment of mange, demodicosis or off‑label high‑dose protocols are much higher and should only be done under a veterinarian’s supervision [6] [3] [1]. Practical guidance cited by veterinarians often equates to about 50 mcg per lb once monthly when using concentrated 1% solutions in some contexts (which translates to ~110 mcg/kg), but manufacturer preventive products use their own calibrated, much lower strengths — so product‑specific instructions matter [3] [6].
5. Toxicity thresholds and breed sensitivity — important clinical limits
Toxic clinical signs in dogs are reported at substantially higher doses (typical toxicity >2 mg/kg for most dogs), but genetic MDR1 sensitivity can produce severe toxicosis at much lower doses (clinical signs reported with doses as low as ~0.1 mg/kg in sensitive dogs); cats have reported clinical signs at ~0.3–0.4 mg/kg [4] [1]. MSD Vet Manual notes that doses many times the normal therapeutic amount produce neurologic effects in large animals, underscoring that “more is not safer” [1].
6. Wide variation, off‑label use, and real‑world cautions
Multiple sources stress that dosing varies by species, product formulation, indication and country approvals; parasiticide technical guides publish “usual” ranges but caution that not all recommendations are approved everywhere and that misuse (e.g., using cattle or horse formulations in small animals) causes accidental overdoses [8] [7] [9]. Consumer forums and clinic Q&A pages show people adapting injectable or horse paste formulas for dogs — practices that veterinary sources warn against because of narrow safety margins and breed genetic risks [3] [4] [9].
Limitations and next steps: these sources provide product‑level label doses (e.g., 200 mcg/kg for cattle/horses) and guidance that small‑animal heartworm prevention uses much lower, product‑specific monthly microdoses, but available sources do not present a single, authoritative weight‑by‑species chart covering every indication and product — consult your veterinarian or the specific product label for the exact mg or mcg per kg and for withholding periods in food animals [5] [6] [7].