Ivermectin for Dogs Dosage Chart
⚡ Key Takeaways: Expert Quick Answers
| ❓ Your Question | ✅ Expert Answer |
|---|---|
| What’s the heartworm prevention dose? | 6 mcg/kg (2.72 mcg/lb) monthly—extremely low and safe |
| Is ivermectin safe for all dogs? | NO—MDR1-mutant breeds can die from standard mange doses |
| Can I use horse/cattle ivermectin? | NEVER—concentration is 100-200x higher than dog products |
| What breeds are at highest risk? | Collies (70%), Australian Shepherds (50%), Shelties, Border Collies |
| How do I know if my dog has MDR1? | Genetic test via cheek swab ($70) from WSU or UC Davis |
| What are toxicity symptoms? | Dilated pupils, tremors, blindness, seizures, coma—within 4-12 hours |
| Is there an antidote? | NO—only supportive care; recovery can take weeks |
| What’s the lethal dose? | Normal dogs: >2.5 mg/kg; MDR1 dogs: as low as 0.1 mg/kg |
🔬 Yes, The FDA Approved It—But Only At Specific Doses For Specific Uses
Let’s establish something critical: The U.S. Food and Drug Administration (FDA) has approved Ivermectin for use in dogs for specific indications. Those indications are extremely narrow, and the approved doses are calculated with precision that DIY dosing cannot replicate.
HEARTGARD® PLUS should be administered orally at monthly intervals at the recommended minimum dose level of 6 mcg of ivermectin per kilogram (2.72 mcg/lb) and 5 mg of pyrantel (as pamoate salt) per kg (2.27 mg/lb) of body weight.
That’s 6 micrograms per kilogram—not milligrams, not a “splash” from a livestock bottle. To put this in perspective:
| 🧪 Measurement | 📊 Equivalence |
|---|---|
| 1 milligram (mg) | 1,000 micrograms (mcg) |
| Heartworm prevention dose | 6 mcg/kg |
| Mange treatment dose | 200-600 mcg/kg |
| Livestock ivermectin concentration | 10,000 mcg per mL (1%) |
In the case of beagle dogs the dose required for prevention of heartworm disease is 6 μg/kg body weight, while the LD50 of this drug in the same breed is 80,000 μg/kg body weight. That sounds like a massive safety margin—until you learn about the genetic landmine waiting in certain breeds.
🧬 The MDR1 Gene: Why “White Feet Don’t Treat” Exists
Here’s the single most important fact in this entire article: A subpopulation of collie dogs is extremely sensitive to neurotoxicity induced by ivermectin. We report a deletion mutation of the mdr1 gene that is associated with ivermectin sensitivity.
This isn’t a minor sensitivity—it’s a potentially fatal genetic defect. In affected dogs, toxicity is caused by doses of ivermectin that are 1/200th of the dose needed to cause toxicity in normal dogs.
What’s happening biologically? The MDR1 gene is responsible for the production of a protein known as p-glycoprotein. This protein acts as a pump in cells, helping to clear chemicals and potential toxins from the cell. In dogs with the mutation, this pump doesn’t work properly, allowing ivermectin to flood into the brain.
In dogs with the MDR1 mutation, defective p-glycoproteins allow higher levels of drugs to enter the brain, increasing the neurologic effects of some medications.
| 🐕 Breed | 📊 Affected Percentage | ⚠️ Risk Level |
|---|---|---|
| Collie (Rough/Smooth) | 70% | 🔴 Extreme |
| Australian Shepherd | 50% | 🔴 Extreme |
| Miniature Australian Shepherd | 50% | 🔴 Extreme |
| Shetland Sheepdog | 15% | 🟠 High |
| English Shepherd | 15% | 🟠 High |
| Old English Sheepdog | 5% | 🟡 Moderate |
| Border Collie | 2-5% | 🟡 Moderate |
| German Shepherd | 10% | 🟠 High |
| Long-haired Whippet | 65% | 🔴 Extreme |
| Silken Windhound | 30% | 🔴 Extreme |
| Mixed breeds with herding ancestry | Unknown | ⚠️ Test first |
The mutation is very common in collies: depending on the source, 55 to 70% of the collie population is affected by this mutation.
Critical distinction: At low doses, such as those used in heartworm prevention, ivermectin is safe even for dogs with the MDR1 mutation. The danger emerges at higher doses used to treat mange, mites, and other parasites.
💊 The Dosage Reality: One Drug, Wildly Different Doses
Here’s what confuses most pet owners: ivermectin doses vary by 50 to 100 times depending on what you’re treating. Dosages as high as 50 to 100 times the amount used to prevent heartworms are used to treat mites on dogs (demodectic mange).
FDA-APPROVED HEARTWORM PREVENTION DOSING
Heartgard dosage is a minimum of 6 mcg/kg (2.72 mcg/lb).
| 🐕 Dog Weight | 💊 Heartgard Product | 📋 Ivermectin Content |
|---|---|---|
| Up to 25 lbs (11 kg) | Blue (Small Dogs) | 68 mcg |
| 26-50 lbs (12-22 kg) | Green (Medium Dogs) | 136 mcg |
| 51-100 lbs (23-45 kg) | Brown (Large Dogs) | 272 mcg |
| Over 100 lbs | Combination of tablets | As directed |
Heartgard has shown a wide margin of safety at the recommended dose level in dogs including pregnant or breeding bitches, stud dogs and puppies aged 6 or more weeks.
OFF-LABEL DOSING FOR OTHER CONDITIONS
This is where things get dangerous. Heartworm prevention: 6 micrograms per kilogram monthly. External parasites: 0.15 mg per pound for two weeks. Internal parasites: 0.1 mg per pound as single dose. Sarcoptic mange: 300-600 micrograms per kilogram weekly. Ear mites: 200-400 micrograms per kilogram as single dose.
| 🎯 Condition | 💉 Dose Range | ⏱️ Frequency | ⚠️ Risk |
|---|---|---|---|
| Heartworm Prevention | 6 mcg/kg | Monthly | ✅ Very Safe |
| Ear Mites | 200-400 mcg/kg | Single dose | 🟡 Moderate |
| Sarcoptic Mange (Scabies) | 200-400 mcg/kg | Every 1-2 weeks x 3-4 | 🟠 Higher |
| Demodectic Mange | 300-600 mcg/kg | Daily for weeks | 🔴 Highest |
| Microfilaria clearance | 50 mcg/kg | Once | 🟡 Moderate |
The dose was increased gradually from 50 microg/kg body weight on day one, 100 microg/kg body weight on day two, 150 microg/kg body weight on day three, 200 microg/kg body weight on day four, to the final dose of 300 microg/kg body weight on day five.
Why the gradual increase matters: Dogs that are heterozygous for the MDR1 gene can also react, although less severely, and similar idiosyncratic reactions may develop in any breed, so a gradually increasing dose (daily progression of 50, 100, 150, 200, then 300 mcg/kg) should be administered to identify susceptible patients.
🚨 Toxicity: What Happens When Things Go Wrong
The clinical signs are typically neurologic in nature (ataxia, lethargy, mydriasis, tremors, blindness, drooling, vomiting, disorientation) and are related to excessive gamma-aminobutyric acid (GABA) receptor activity in the central nervous system.
TIMELINE OF SYMPTOMS
Clinical signs usually develop within a few hours but may be delayed for up to 24 hours.
| ⏰ Time Post-Exposure | 🩺 Symptoms |
|---|---|
| 2-4 hours | Dilated pupils, drooling, mild incoordination |
| 4-12 hours | Severe ataxia, disorientation, vomiting, tremors |
| 12-24 hours | Blindness, recumbency, inability to stand |
| 24-48 hours | Seizures, coma, respiratory depression |
| Without treatment | Death from respiratory failure |
Signs and symptoms of toxicity: Clinical signs of toxicity include fatigue, difficulty walking, increased saliva production, dilated pupils, blindness, and seizures.
DOSE THRESHOLDS FOR TOXICITY
For most dogs signs of toxicosis may be seen at doses greater than 2 mg/kg (0.9 mg/lb). Dogs affected by genetic sensitivity can have toxicosis with as little as 0.1 mg/kg (0.04 mg/lb).
| 🐕 Dog Type | ⚠️ Toxic Threshold | 💀 Lethal Potential |
|---|---|---|
| Normal dogs | >2.5 mg/kg | >5 mg/kg |
| MDR1 heterozygous | 0.3-0.5 mg/kg | >1 mg/kg |
| MDR1 homozygous | 0.1 mg/kg | >0.2 mg/kg |
| Puppies (immature BBB) | Lower than adults | Higher sensitivity |
However, certain dogs, primarily rough-coated collies, exhibit signs of toxicity when given ivermectin at doses in the range of 100–2500 μg/kg body weight.
🏥 Treatment: There Is No Antidote
There is no specific antidote for ivermectin toxicosis.
Let that sink in. If your dog develops ivermectin toxicity, veterinarians can only provide supportive care and hope the drug clears before irreversible damage occurs.
Most dogs with signs of ivermectin toxicity will need to be hospitalized and placed on IV fluids for hydration and supportive care. Medications will be given to treat the symptoms of vomiting and diarrhea, as well as for muscle twitching and seizures.
WHAT TREATMENT LOOKS LIKE
| 🏥 Intervention | 📋 Purpose |
|---|---|
| IV Fluids | Hydration, support circulation |
| Intubation/Ventilator | Respiratory support if breathing fails |
| Seizure medications | Phenobarbital, propofol for convulsions |
| Lipid emulsion therapy | May help pull ivermectin from tissues |
| Feeding tubes | Nutritional support for comatose dogs |
| Temperature regulation | Hypothermia prevention |
| Rotating patient | Prevent pressure sores |
Recovery from ivermectin toxicity can vary from days to weeks.
If the drug was given within the past 4 – 6 hours, your veterinarian may induce vomiting and/or give your dog activated charcoal to help minimize the amount of ivermectin that is absorbed.
The terrifying reality: The worse case that I saw where the dog survived was an Australian Shepherd from Montana who became exposed after licking up a dollop of dewormer that had dropped out of a horse’s mouth when the owner was deworming it. The dog was flown on a private jet to WSU, with a private vet tech hired to breathe for the dog.
🐴 Why Livestock Ivermectin Is Absolutely Not For Dogs
Veterinary professionals are increasingly concerned about the number of pet owners searching for ivermectin dosage charts as though it’s a DIY tool. But here’s the raw truth: there’s no one-size-fits-all chart for ivermectin in dogs—because a safe dose depends on genetics, weight, indication, and formulation.
The math explains the danger:
| 🧴 Product | 📊 Concentration | ⚠️ Comparison to Heartgard |
|---|---|---|
| Heartgard (25 lb dog) | 68 mcg total | Baseline |
| Ivomec 1% Injectable | 10,000 mcg/mL | 147x per mL |
| Horse paste 1.87% | 18,700 mcg/mL | 275x per mL |
| Cattle pour-on 0.5% | 5,000 mcg/mL | 74x per mL |
Note that the common recommendation to give 0.1 cc undiluted ivermectin per 10 pounds of body weight provides 37 times the amount of ivermectin needed for heartworm prevention.
Livestock-treated manure contains ivermectin residues that can linger for weeks. A dog licking manure or residue can ingest enough to induce CNS depression, especially if the animal is small, geriatric, or genetically susceptible.
🧪 Genetic Testing: Your Dog’s Life Insurance Policy
This test identifies the well-known and relatively widespread 4-bp deletion associated with multidrug sensitivity in several purebred and mixed-breed dogs.
WHERE TO GET TESTED
| 🏛️ Laboratory | 💵 Cost | 🔬 Method |
|---|---|---|
| Washington State University VCPL | ~$70 | Cheek swab |
| UC Davis VGL | ~$50-80 | Cheek swab |
| Embark DNA | Included in panel | Cheek swab |
| Wisdom Panel | Included in panel | Cheek swab |
Finding out if your dog has the MDR1 mutation is easy. A simple cheek swab can be taken at home and mailed to the Veterinary Clinical Pharmacology Laboratory at Washington State University.
TEST RESULTS INTERPRETATION
Normal/Normal – These dogs do not carry the mutation, and will not pass on the mutation to their offspring. These dogs would not be expected to experience unexpected adverse drug reactions to normal doses of ivermectin, loperamide (Imodium) and some anticancer drugs.
Mutant/Mutant – These dogs carry the mutation and will pass on the mutant gene to their offspring. These dogs would be expected to experience toxicity after normal doses of loperamide (Imodium) and some anticancer drugs, and high doses of ivermectin (greater than 50 micrograms per kilogram.)
| 🧬 Result | 📋 Meaning | ⚠️ Risk Level |
|---|---|---|
| Normal/Normal | No mutation | ✅ Standard dosing OK |
| Normal/Mutant | One copy (carrier) | 🟡 Some sensitivity possible |
| Mutant/Mutant | Two copies (affected) | 🔴 Severe sensitivity |
💊 Drug Interactions: The Hidden Danger
Ivermectin doesn’t exist in a vacuum. Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any treatment.
DANGEROUS COMBINATIONS
| 💊 Drug | ⚠️ Interaction |
|---|---|
| Spinosad (Comfortis, Trifexis) | Increased ivermectin toxicity risk |
| Ketoconazole | Increases ivermectin blood levels |
| Cyclosporine | Inhibits P-glycoprotein |
| Erythromycin | Increases ivermectin absorption |
| Loperamide (Imodium) | Same MDR1 sensitivity applies |
Do not combine high doses of ivermectin used to treat mange with any product that uses spinosad, including Comfortis and Trifexis.
✅ Safe Alternatives For MDR1-Sensitive Breeds
Milbemycin oxime (e.g., Interceptor®): A heartworm preventive also effective against roundworms, hookworms, and whipworms. Safer for MDR1-sensitive breeds. Selamectin (e.g., Revolution®): A topical option used for heartworm prevention and treatment of fleas, ear mites, and sarcoptic mange. Moxidectin (e.g., Advantage Multi®, ProHeart®): Available in topical and injectable forms.
| 💊 Alternative | 🎯 Uses | 🐕 MDR1 Safety |
|---|---|---|
| Milbemycin (Interceptor) | Heartworm, intestinal worms | ✅ Safe at prevention doses |
| Selamectin (Revolution) | Heartworm, fleas, ear mites | ✅ Generally safe |
| Moxidectin (ProHeart) | Heartworm (6-12 months) | ✅ Safe at labeled doses |
| Isoxazolines (Simparica, Bravecto) | Fleas, ticks, mange | ✅ Not affected by MDR1 |
This group of compounds is highly efficacious against Demodex spp and has become the treatment of choice for demodicosis in dogs and cats. The newer isoxazoline class (fluralaner, afoxolaner, sarolaner) has largely replaced high-dose ivermectin for mange treatment because they don’t carry MDR1 risks.
📋 The Bottom Line: What Vets Actually Want You To Know
| 🎯 Situation | 💡 Expert Recommendation |
|---|---|
| Heartworm prevention | Use FDA-approved products—safe for virtually all dogs |
| Herding breed mix | Test for MDR1 before ANY off-label ivermectin use |
| Mange treatment needed | Ask about isoxazolines (Bravecto, Simparica) instead |
| Found livestock ivermectin | PUT IT DOWN—the math is too dangerous |
| Saw toxicity symptoms | Emergency vet IMMEDIATELY—minutes matter |
| Want to save money | Generic heartworm preventives exist—ask your vet |
| Dog ate horse paste | Call Pet Poison Helpline: (855) 764-7661 |
FDA-approved heartworm preventatives are not only meticulously dosed for each weight category, but they also undergo rigorous safety and efficacy trials specific to dogs.
Ivermectin toxicosis primarily varies in the amount of drug consumed, with higher doses producing more severe intoxication.
The veterinary profession has spent decades refining ivermectin dosing precisely because the consequences of getting it wrong are catastrophic. This medication should take effect within one to two hours; however, effects may not be visibly noticed, and so laboratory tests may be required to evaluate this medication’s effectiveness.
Your dog’s life shouldn’t be a DIY project. The $10 you might save using livestock formulations isn’t worth the $5,000 ICU bill—or the grief of losing your best friend to a preventable poisoning. Get the genetic test. Use approved products. Trust your veterinarian’s dosing calculations. Because in the world of ivermectin, precision isn’t just important—it’s life or death.
