Ivermectin for dogs is a widely used antiparasitic drug that appears in FDA-approved canine heartworm preventives and, at much higher doses, in veterinarian-directed treatment of mange mites. At the low monthly doses used for heartworm prevention it has a long safety record in most dogs — but it is also a drug with a genuinely narrow margin in certain herding breeds, and the livestock and horse formulations sold in feed stores are labeled for those species only. If you are trying to work out where human ivermectin can legally be bought, that is a separate question; for dogs, the short answer is a veterinarian, because the canine products are prescription-only.

This page explains what the approved canine labeling covers, how dosing is calculated by body weight, why collies and related breeds need genetic testing first, and what overdose looks like. Livestock and equine products such as ivermectin horse paste and ivermectin pour-on for cattle are labeled for animal use only in the species named on the carton, are not approved for people, and are not measurable into a safe canine dose at home. The same species limits apply to cats, and ivermectin safety in cats is covered on a separate page. Prices, prescription status and state laws in this article were last verified in March 2026.

Key takeaways

  • Heartworm preventives containing ivermectin are FDA-approved for dogs at roughly 6 micrograms per kilogram per month — a tiny fraction of the doses used for mites.
  • Dogs with the MDR1 (ABCB1) gene mutation, common in collies and other herding breeds, can develop severe neurologic toxicity at doses other dogs tolerate easily.
  • Canine heartworm products require a prescription and a negative heartworm test; they are not legally sold over the counter for dogs in the US.
  • Ivermectin formulations for horses, cattle, sheep and swine are labeled for animal use only in those species and are not approved for people or for dogs.
  • Overdose signs are neurologic — stumbling, tremors, dilated pupils, drooling, blindness — and are a same-day emergency.

Is ivermectin safe for dogs?

Veterinarian's gloved hands preparing a skin scraping slide to check a dog for mange mites

At approved preventive doses, yes, for most dogs. VCA Animal Hospitals' drug monograph states that ivermectin is generally well tolerated at the doses used for heartworm prevention, with side effects appearing at higher doses. PetMD notes that ivermectin is approved for use in dogs at oral doses up to about 0.024 mg/kg, while most dogs tolerate substantially more without problems — which is why the monthly preventive dose sits far below the threshold at which toxicity is normally seen.

The safety picture changes in three situations. First, in dogs carrying the MDR1 mutation, where the blood–brain barrier does not clear the drug normally. Second, when a dog with circulating heartworm microfilariae is given ivermectin: VCA warns that killing large numbers of larvae can trigger a shock-like reaction with weakness, vomiting, diarrhea and pale gums, which is part of why a negative heartworm test is required before starting a preventive. Third, when the dose comes from a concentrated livestock product rather than a canine one.

That third point deserves repeating. Injectable cattle and equine ivermectin products are concentrated for animals weighing hundreds of kilograms. Older veterinary literature is explicit that cattle labeling has warned severe adverse reactions, including fatalities in dogs, may follow use in other species. These products are labeled for animal use only in the species named on the label, are not approved for human use, and diluting or eyeballing them for a dog is how accidental overdoses happen.

Veterinary uses (heartworm prevention, mites)

Gloved hands drawing a measured dose into a graduated oral dosing syringe next to a plastic veterinary paste syringe

Heartworm prevention

This is the core approved use. Ivermectin is combined with pyrantel in beef-flavored chewables given once monthly; the ivermectin blocks development of heartworm larvae acquired in the previous month, while pyrantel treats and controls hookworms and roundworms, according to product information published by 1-800-PetMeds. Veterinary clinical material reviewed through VIN describes ivermectin as microfilaricidal at preventive doses of roughly 6–12 mcg/kg per month, producing a gradual decline in microfilarial numbers.

Preventives work retroactively on the previous month's exposure, which is why dosing on schedule matters more than dosing heavily. VCA advises that if more than eight weeks have passed without a dose, you should contact your veterinarian rather than double up — and never give two doses at once.

Mange and other external parasites

Ivermectin is also used, largely off-label under veterinary direction, for sarcoptic mange (scabies) and demodectic mange. These doses are dramatically higher than preventive doses — demodicosis protocols commonly run in the range of 300–600 mcg/kg, sometimes daily for weeks to months, versus about 6 mcg/kg once a month for heartworm prevention. That is a 50- to 100-fold difference, which is precisely why an accurate diagnosis, MDR1 status and veterinary supervision are non-negotiable before a mange protocol starts. Ivermectin is not a treatment for adult heartworm infection, and it does not replace adulticide therapy.

Dosage by weight

Cheek swab sample being collected from a rough-coated collie for MDR1 genetic testing

Canine ivermectin dosing is calculated on body weight in kilograms, and approved chewables are pre-portioned into weight bands so owners never have to measure the drug themselves. The table below summarizes the published weight bands for ivermectin/pyrantel chewables alongside the general dose ranges described in veterinary sources. It is reference information, not a dosing instruction — the ivermectin dog dose for any individual animal comes from the prescribing veterinarian.

Use Approximate dose range Frequency Status
Heartworm prevention ~6–12 mcg/kg (≈2.7–5.5 mcg/lb) Once monthly, year-round FDA-approved, prescription
Chewable weight bands 68 mcg (up to 25 lb); 136 mcg (26–50 lb); 272 mcg (51–100 lb) Once monthly Per product labeling; over 100 lb uses combinations
Sarcoptic mange ~200–400 mcg/kg Repeated at vet-specified intervals Extra-label, vet-directed
Demodectic mange ~300–600 mcg/kg Often daily, weeks to months Extra-label, vet-directed

Two practical notes on dog ivermectin dosage. Underdosing a preventive is not a safe hedge — it can leave a dog unprotected while still exposing it to the drug. And the arithmetic that circulates online for converting horse paste or cattle pour-on into a canine dose is unreliable, because those products are labeled for animal use only in the species on the carton, are not approved for people, and are not formulated for accurate microgram dosing of a 10-pound dog. Our overview of canine ivermectin formulations covers the differences in concentration between product types.

Breeds at risk: MDR1 gene and collies

Veterinary receptionist's hands passing a plain white medication carton and paper bag across a clinic counter to a customer

Ivermectin sensitivity in collies was traced by Mealey and colleagues, published in Pharmacogenetics in 2001 and indexed on PubMed, to a 4-base-pair deletion in the mdr1 gene. The gene encodes P-glycoprotein, a transport pump in the blood–brain barrier that normally moves ivermectin out of brain tissue. The deletion causes a frameshift and premature stop codons, so the protein is truncated and nonfunctional. Dogs homozygous for the deletion show the ivermectin-sensitive phenotype; homozygous-normal and heterozygous dogs do not show it to the same degree, though heterozygotes can still react to some drugs at higher doses.

Washington State University's veterinary pharmacology program, which discovered the mutation and developed the first diagnostic test, reports that up to 75% of dogs in some herding breeds carry it, along with about 4% of cats, and that affected animals can experience tremors, blindness and death from drugs a normal dog clears easily. Testing is a cheek swab or blood sample; MedVet notes puppies should be weaned before sampling, since cells from the mother's milk can produce a false positive.

Breeds where testing is routinely recommended include:

  • Rough and smooth Collie, Border Collie, Shetland Sheepdog
  • Australian Shepherd and Miniature American Shepherd
  • Old English Sheepdog, English Shepherd, McNab
  • Long-haired Whippet and Silken Windhound
  • German Shepherd Dog and herding-breed mixes of unknown ancestry

Importantly, MDR1-affected dogs can usually take standard monthly heartworm preventives safely — the risk concentrates at the much higher doses used for mange, and with certain other P-glycoprotein substrate drugs. Confirm with your veterinarian rather than assuming either way.

Side effects and overdose signs

VCA lists the adverse effects that warrant an immediate call: serious neurologic signs including stumbling, trembling, dilated pupils, drooling or head pressing, and shock-like signs if the drug is killing large numbers of heartworm larvae. Ivermectin is short-acting at normal doses, with effects generally resolving within about 24 hours, though clearance is slower in dogs with liver or kidney disease.

Overdose is a neurologic emergency. PetMD advises contacting a veterinarian immediately if a dog receives the wrong weight-band product or eats more than one monthly dose. Treatment is largely supportive, and severe cases may require days of intensive care. A 2025 case report in Veterinary Medicine and Science, indexed on PubMed, described a 2.5 kg Shih Tzu with ataxia, tremors, absent pupillary light and menace responses, bradycardia and salivation after ingesting a 10 mg ivermectin tablet; neurologic signs began improving about 2.5 hours after intravenous lipid emulsion therapy and had resolved by 24 hours. That single case is not proof of a standard protocol, but it illustrates both the severity and the fact that outcomes depend on getting to a clinic fast.

Where to buy it

Canine ivermectin heartworm products are prescription items in the US. Retail listings at Walmart and 1-800-PetMeds both state that a prescription is required, and the manufacturer's own offers page says rebates can be claimed once the dog has a negative heartworm test and a prescription from a veterinarian. Legitimate sources are therefore veterinary clinics and licensed pet pharmacies that verify the prescription with your vet.

On cost, GoodRx's pet medication page for ivermectin/pyrantel chewables listed prices from about $90.69 with a coupon as of early 2026, with manufacturer rebates of $15 to $40 advertised on multi-dose purchases; Walmart listings for six-month supplies started around $59.59 depending on weight band. Pet drug pricing moves frequently, so treat these as a snapshot verified in March 2026 rather than a current quote.

A point of frequent confusion: several states changed their human ivermectin rules in 2025. Pharmacy Times reported that four states passed laws permitting over-the-counter sale of human ivermectin, and Idaho's Division of Occupational and Professional Licenses issued guidance in January 2026 on its 2025 statute allowing ivermectin suitable for human use to be sold without a prescription or consultation. Arkansas enacted a comparable law in 2025. None of those laws change anything about dogs: they govern human-labeled products, they do not authorize dosing a pet, and veterinary formulations remain animal-use-only products that are not approved for people.

Frequently asked questions

Can I use ivermectin horse paste on my dog?

It is labeled for use in horses only, is not approved for people, and is not designed for microgram-accurate dosing of a small animal. Veterinary sources have long warned that livestock formulations have caused severe reactions and deaths in dogs. If a veterinarian ever elects to use a non-canine formulation, that is an extra-label decision made with a dose calculation you should not attempt independently.

What is the ivermectin dog dosage for heartworm prevention?

Veterinary references describe roughly 6–12 mcg/kg once monthly, delivered through pre-portioned chewables in fixed weight bands. Your veterinarian selects the band by current body weight, which matters most in growing puppies.

How soon does ivermectin work for mange?

Mange protocols typically run for weeks to months, with repeat skin scrapings to confirm mites are gone. Itching often improves before the infestation is actually cleared, which is why stopping early is discouraged.

Is ivermectin safe for puppies?

Ivermectin/pyrantel chewables are labeled for dogs six weeks of age and older with no minimum weight, per product information published by 1-800-PetMeds. Higher off-label doses in very young puppies are a separate question for your veterinarian.

Should I test my mixed-breed dog for MDR1?

If herding-breed ancestry is plausible or unknown, WSU's program supports testing, since the mutation appears in mixed-breed dogs too. The result is useful beyond ivermectin, because it affects several other commonly prescribed drugs.

Does a missed dose need a heartworm test?

VCA advises contacting your veterinarian if more than eight weeks have elapsed without a dose. Retesting is often recommended, because a preventive given to an already-infected dog can cause a reaction.

Sources