Ivermectin for Cats: Dosage, Safety and Alternatives
By Dr. Zubair Khalid, DVM, MS, PhD ·
Ivermectin for cats dosage is not something you can safely guess at home. The drug is a potent antiparasitic with a narrow margin between a helpful dose and a dangerous one, and cats are far more sensitive to it than dogs. Most owners should never calculate this dose themselves, because the difference between a safe amount and a toxic one can be a fraction of a milliliter.
This article is educational and is not a substitute for veterinary diagnosis or treatment.
Quick Answer
- Ivermectin is a prescription antiparasitic. A veterinarian decides the dose based on your cat's exact weight, the condition being treated, and the product's concentration.
- Cats are unusually vulnerable to ivermectin and related drugs because of a genetic difference in a drug transporter called P-glycoprotein. Cats with two copies of a specific mutation (ABCB11930_1931del TC) can develop severe neurotoxicity even at labeled doses of some products [1][2].
- Never use a livestock, cattle, or horse ivermectin product on a cat. Concentrations differ enormously, and a tiny error can cause poisoning.
- Selamectin is often the safer, better-studied choice for routine parasite prevention in cats, and it carries a much lower reported risk of neurologic reactions [1].
- If you suspect your cat received too much ivermectin, call your veterinarian or a pet poison hotline immediately. Do not wait for symptoms to appear.
What Ivermectin Is and What Veterinarians Use It For
Ivermectin belongs to a family of drugs called macrocyclic lactones. These medications kill parasites by disrupting their nervous systems. In veterinary medicine, ivermectin has been used for decades to treat and prevent a range of internal and external parasites.
In cats, veterinarians sometimes use ivermectin for specific, targeted situations. One example is a rare neurologic parasitic condition called neurocuterebriasis, where a botfly larva migrates into the nervous system. In a series of 13 cats with presumptive neurocuterebriasis, a three-day protocol using ivermectin at 0.4 mg/kg alongside diphenhydramine and dexamethasone was used, and the earlier version of this protocol in three cats produced no adverse effects [3]. That is a specialist decision made in a referral setting, not a home treatment.
Ivermectin also appears in some topical combination products. A field study of 142 cats evaluated a topical formulation combining ivermectin, imidacloprid, and praziquantel for flea control and found effective flea reduction after a single application [4]. This shows ivermectin can be part of a legitimate, vet-guided parasite plan when the product is made for cats and used exactly as directed.
What ivermectin is not is a general-purpose dewormer you can grab off a farm store shelf and dose by eye. The margin for error is small, and the consequences of getting it wrong can be permanent or fatal.
How Ivermectin Works
Ivermectin opens channels in the nerve and muscle cells of parasites, which paralyzes and kills them. The drug targets channels that parasites rely on heavily.
The problem is that these same channels exist in mammals, including cats. In most animals, a pump called P-glycoprotein keeps ivermectin out of the brain by pushing it back across the blood-brain barrier. When that pump works normally, the drug stays largely where it should and the brain is protected.
Some cats have a genetic variant that makes this pump non-functional. Cats homozygous for the ABCB11930_1931del TC mutation have a broken P-glycoprotein system, so ivermectin and similar drugs can accumulate in the brain and cause neurotoxicity [2]. This is why a dose that seems reasonable on paper can still poison a cat.
Ivermectin for Cats Dosage: What Owners Need to Understand
Who decides the dose
Your veterinarian does. There is no safe universal ivermectin dose for cats, and there is no reliable home dosage chart you should follow. The correct amount depends on your cat's weight, the parasite being treated, the concentration of the specific product, and your cat's overall health and genetics.
If you see an ivermectin for cats dosage chart by weight online, treat it with suspicion. A chart cannot account for product concentration differences or for your cat's P-glycoprotein status.
Why concentration differences matter so much
Ivermectin comes in wildly different strengths. A product made for cattle or horses may contain many times the concentration found in a cat-labeled product. When owners try to convert a large-animal dose down to a cat, the math often goes wrong, and even a small measuring error becomes a large overdose.
This is also why ivermectin for cats dosage in ml is such a risky search. Milliliters only make sense when you know the milligrams per milliliter of that exact product. Two bottles with the same volume can contain completely different amounts of drug.
How it is given
Ivermectin for cats is typically given either by mouth or applied topically, depending on the product. Your veterinarian will tell you which route and which product to use. Follow the label and the prescription exactly. Do not split, combine, or substitute products.
Missed doses
If you miss a dose, do not double up to catch up. Call your veterinarian's office and ask how to proceed. Doubling a dose is one of the most common ways cats get poisoned.
Side Effects: Common and Serious
| Side effect | How common or serious | What to do |
|---|---|---|
| Mild digestive upset (drooling, soft stool) | Uncommon at correct doses, usually mild | Monitor, call your vet if it persists |
| Sleepiness or mild lethargy | Possible, usually short-lived | Watch closely, call your vet if it worsens |
| Dilated pupils (mydriasis) | A warning sign of neurotoxicity | Call your vet the same day |
| Wobbly walking (ataxia) | Serious, seen in macrocyclic lactone toxicosis | Emergency visit now |
| Generalized weakness | Serious, seen in toxicosis | Emergency visit now |
| Tongue protrusion or trouble swallowing (glossal paresis) | Serious and characteristic of eprinomectin toxicosis | Emergency visit now |
| Tremors, seizures, coma | Life-threatening | Emergency visit now |
The neurologic signs above are the ones that matter most. In documented cases of macrocyclic lactone toxicosis in cats, mydriasis, ataxia, generalized weakness, and glossal paresis were typical findings, and blood work was often normal [5]. That last point is important. A normal blood panel does not rule out toxicity.
Glossal paresis deserves special mention. When a cat cannot use its tongue normally, it cannot eat or drink well, and nutritional support that bypasses the mouth may be needed during recovery [5]. This is a hospital-level problem, not something to manage at home.
Who Should Not Take Ivermectin, and What Interacts With It
Cats with a known MDR1 mutation, or cats whose genetics are unknown but who have reacted badly to a macrocyclic lactone before, should not receive ivermectin without a serious conversation with a veterinarian. In one case series, 26 of 27 cats with toxicosis were linked to eprinomectin, and 21 of those 26 were homozygous for the MDR1 mutation [1]. Genetics clearly drives much of this risk.
Certain drugs should be avoided in a cat being treated for macrocyclic lactone toxicosis. Central nervous system depressants and other P-glycoprotein substrates can worsen or prolong the poisoning and should be avoided [5]. Always tell your veterinarian every medication, supplement, and parasite product your cat receives, including anything you bought without a prescription.
If your cat takes other medications, ask about interactions before starting any ivermectin product. This is also a good habit with common owner-administered drugs. Our guides on Benadryl dosing and safety for cats and melatonin safety for cats explain how even over-the-counter products need a vet's input.
Overdose: What to Do Right Now
There is no antidote for macrocyclic lactone toxicosis [5]. Treatment is supportive, and it can take a long time. One cat that developed toxicity after a routine labeled application of an eprinomectin-containing product took three months to make a complete recovery [2].
Intravenous lipid emulsion therapy has been used successfully in ivermectin overdose in a dog, with neurologic symptoms improving within hours [6]. However, this treatment may not be effective in cats homozygous for the MDR1 mutation [5]. That means prevention and early recognition matter far more than any rescue therapy.
If you think your cat got too much ivermectin:
- Call your veterinarian or an emergency clinic immediately, even if your cat seems fine.
- Call a pet poison hotline if your regular vet is closed. Have the product bottle, the concentration, and your cat's weight ready.
- Do not induce vomiting unless a veterinarian tells you to.
- Do not give other medications to "counteract" the ivermectin. Some can make things worse [5].
Time matters. The sooner treatment starts, the better the odds.
Selamectin: Often the Safer Choice
Selamectin is a macrocyclic lactone too, but it has a different safety profile in cats. In a pharmacovigilance review of topical macrocyclic lactone products, neurologic adverse event reporting was compared across products, and the data provide comparative context for veterinarians choosing among them [7].
The genetic data are more striking. When researchers looked at cats that developed neurotoxicity after labeled doses of eprinomectin- or selamectin-containing products, 26 of 27 cases involved eprinomectin, and only 1 involved selamectin [1]. That does not make selamectin risk-free, but it does help explain why many veterinarians reach for it first.
If your cat needs flea, tick, or heartworm prevention, ask your veterinarian whether a selamectin-based product fits. Our Revolution Plus dose guide for cats walks through how selamectin and sarolaner dosing works. For heartworm prevention specifically, our Heartgard Plus ivermectin and pyrantel guide explains how ivermectin is used in that context.
Limitations and When to Contact a Veterinarian
This article cannot tell you the right dose for your cat. Only your veterinarian can, after examining your cat and reviewing its weight, history, and current medications.
Contact your veterinarian the same day if you notice dilated pupils, mild wobbliness, unusual sleepiness, drooling, or any change in behavior after an ivermectin product.
Go to an emergency clinic right now if your cat has trouble walking, cannot hold its head up, has a protruding tongue, cannot swallow, has tremors, or has a seizure. These are signs of neurotoxicity and they can progress quickly [5].
Schedule a routine visit if you are unsure whether your current parasite prevention is appropriate, if you have been using a product not prescribed for your cat, or if you want to discuss genetic testing for the MDR1 mutation.
Frequently Asked Questions
Can I use livestock ivermectin on my cat?
No. Livestock products are far more concentrated than cat-labeled products, and measuring errors are common and dangerous. Cats have a narrow safety margin with this drug, and some cats are genetically unable to clear it from the brain [2]. Use only a product prescribed by your veterinarian for your cat.
How do I know if my cat is one of the sensitive ones?
Genetic testing can identify cats homozygous for the ABCB11930_1931del TC mutation, which causes a non-functional P-glycoprotein pump [2]. Your veterinarian can arrange this testing. If your cat has reacted badly to a macrocyclic lactone before, tell every veterinarian you see from then on.
Is selamectin safer than ivermectin for cats?
Selamectin appears to carry a much lower reported risk of neurologic toxicity in cats. In one case series, 26 of 27 cats with macrocyclic lactone toxicosis were linked to eprinomectin, with only one linked to selamectin [1]. Ask your veterinarian whether a selamectin product is right for your cat.
What happens if my cat gets too much ivermectin?
There is no antidote, so treatment is supportive and may take weeks to months [5][2]. Signs include dilated pupils, weakness, wobbliness, and tongue problems. Call your veterinarian or a pet poison hotline immediately, even before symptoms start.
Can ivermectin be used for flea control in cats?
Yes, in specific cat-labeled combination products and under veterinary guidance. A field study of a topical ivermectin, imidacloprid, and praziquantel product showed effective flea control in cats after a single application [4]. Never use a product that is not labeled for cats or not prescribed for your cat.
Related Articles
- Revolution Plus for Cats: Selamectin Sarolaner Feline Dose Guide
- Can I Give My Cat Melatonin? Safety, Dosage, and When to Avoid It
- Can You Give Your Cat Benadryl? Dosage and Safety Guide
- Onsior Robenacoxib for Cats: Feline NSAID Safe Dosing Protocol
- Heartgard Plus Dose: Ivermectin Pyrantel Prevention Guide
- Amoxicillin Dog Cat Dose: Broad-Spectrum Antibiotic Weight-Based Guide
References
- Avermectin-induced neurotoxicity and mortality reported more commonly in cats homozygous for ABCB11930_1931del TC after application of eprinomectin- versus selamectin-containing products. Journal of the American Veterinary Medical Association, 2025.
- Inherent P-glycoprotein deficiency and macrocyclic lactone toxicity in an Australian Maine Coon cat homozygous for ABCB11930_1931del TC. JFMS open reports, 2026.
- Antemortem diagnostic tests and treatment outcomes using ivermectin in 13 cases of presumptive feline neurocuterebriasis. The Canadian veterinary journal = La revue veterinaire canadienne, 2025.
- Field evaluation of a topical combination of ivermectin, imidacloprid, and praziquantel for flea control in cats under routine clinical. Frontiers in parasitology, 2026.
- Management of Eprinomectin Neurotoxicosis in Cats. Journal of veterinary emergency and critical care (San Antonio, Tex. : 2001), 2026.
- Intralipid emulsion therapy for ivermectin toxicity in a dog. Veterinary medicine and science, 2025.
- Topically administered macrocyclic lactone products, including eprinomectin, demonstrate comparable neurological safety in cats based on pharmacovigilance data. Journal of the American Veterinary Medical Association, 2026.