Neomec (Ivermectin)

What it’s used for          Side effects          Dosage

Neomec (Ivermectin) is poisonous and dangerous in the wrong dosage.

Don’t kill your dog by giving it the wrong dose.

Now stand at ease and read on.

Despite the dramatic warning, Ivermectin (that’s the name of the drug; Neomec is just one of its many brand names) has been hailed as a wonder drug. Its discovery led to the Nobel Prize for Medicine being awarded in 2015 to the two scientists who discovered it, William C. Campbell and Satoshi Ōmura.

What it’s used for

In veterinary use, it treats many intestinal worms (but not tapeworms), most mites, and some lice. That includes mange.

Neomec (Ivermectin) is not effective for eliminating ticks, flies, flukes, or fleas. That is because the eggs and larvae on the floor will mature and come back to the host. It is effective against larval heartworms, but not against adult heartworms, though it may shorten their lives. The dose of the medicine must be very accurately measured, as it is very toxic in over-dosage. It is sometimes administered in combination with other medications to treat a broad spectrum of animal parasites. Some dog breeds (especially the Rough Collie, the Smooth Collie, the Shetland Sheepdog, and the Australian Shepherd), though, have a high incidence of a certain mutation within the MDR1 gene (coding for P-glycoprotein); affected animals are particularly sensitive to the toxic effects of Ivermectin. Clinical evidence suggests kittens are susceptible to Ivermectin toxicity. (Ed. – In other words, it poisons them.)


Interestingly for Kolkata, research is currently underway to see if Ivermectin is effective in treating chikungunya in humans.

Side effects

In some dogs (those with an MDR1 gene mutation), Neomec (Ivermectin) has dangerous side effects that affect the brain and nervous system, and the liver. For the latter reason, some (but not all) vets prescribe a liver protector, such as Liv-52, to be given with the Neomec. There is a test (which may or may not be available in Kolkata) to see if an individual animal has that gene mutation. Some dog breeds have a high incidence of adverse reaction.

Side Effects of Ivermectin in Cats

In cats, ivermectin has a fairly high margin of safety. When seen, side effects include:

  • agitation
  • crying
  • lack of appetite
  • dilated pupils
  • paralysis of hind legs
  • muscle tremors
  • disorientation
  • blindness
  • other neurological signs, such as head pressing or wall climbing

If your cat is receiving ivermectin and you notice these types of symptoms, discontinue the medication and contact your veterinarian.

Side Effects of Ivermectin in Dogs

In dogs, the risk of side effects associated with ivermectin depends on the dosage, on the susceptibility of the individual dog and on the presence of heartworm microfilaria (a larval form of the heartworm.)

When used at a low dose for heartworm prevention in a dog free of heartworms, ivermectin is relatively safe. At higher doses which may be used for treating other parasitic infections, the risk of side effects increases. Potential side effects include:

  • vomiting
  • dilated pupils
  • muscle tremors
  • blindness
  • incoordination
  • lethargy
  • lack of appetite
  • dehydration

When used in a dog infected with heartworms, a shock-like reaction believed to be caused by dying microfilaria can occur. This type of reaction may be accompanied by lethargy, a low body temperature and vomiting. Dogs testing positive for heartworms should be observed closely for at least 8 hours following the administration of ivermectin.

Ivermectin Sensitivity in Collies and Similar Breeds

Neurotoxicity can also occur with ivermectin usage in some dogs. This is particularly common in dogs that have a genetic mutation known as the MDR1 (multi-drug resistance) gene mutation. This gene mutation is known to occur most commonly in breeds such as Collies, Australian Shepherds, Shelties, Long-haired Whippets and other breeds with “white feet.”

Symptoms of neurotoxicity include incoordination, muscle tremors, seizures, blindness and death.

Ivermectin used at dosages used for heartworm prevention is generally safe for these dogs. However, the drug should not be used at higher doses for dogs that may possess the MDR1 gene mutation. There is a test that can be performed to check for the gene mutation.


A vet writes about the safe use and dangers of Neomec (Ivermectin)

The owners were unaware of what had happened until the dogs began to fall ill. Treatment had failed to save the puppy that developed symptoms first. Meanwhile two more had died, and the owners called me out to euthanize the sole remaining puppy that was in a coma.
My clients were obviously heartbroken and felt terrible that their puppies had died from a preventable poisoning. Let me take this opportunity to review some basic information about ivermectin.

Ivermectin is a member of the macrocytic lactone class of parasiticides. It is commonly used as a heartworm preventative in small animals and for the treatment of certain types of external (e.g., mites) and internal parasites in many different species. The difference between the safe use of ivermectin and poisoning is all about the dose and an animal’s inherent sensitivity to the drug. Some dogs carry a gene (MDR1 or ABCB1) that makes doses of ivermectin and other drugs that are safe for the general population dangerous to those individuals.

I’m going to focus on dogs from here on out since they were involved in 282 of the 318 potentially toxic ivermectin exposures reported to the ASPCA Animal Poison Control Center during 2008–2009. Typical doses for ivermectin in dogs are:

  • 6 ug/kg for heartworm prevention
  • 300 ug/kg for treatment of sarcoptic mange
  • 400-600 ug/kg for treatment of demodectic mange

Non-sensitive breeds generally need to be exposed to more than 2,000 ug/kg before significant symptoms develop, but the potentially toxic dose in MDR1 positive individuals can be as low as 100 ug/kg. Take note that the incredibly low dose used for heartworm prevention is well below the toxic dose even for even the most sensitive dogs. Before using higher doses of ivermectin, however, at risk dogs can be tested for the MDR1 gene mutation. This is especially important for breeds like Collies, Shetland Sheepdogs (Shelties), Australian Shepherds, Old English Sheepdogs, English Shepherds, German Shepherds, Long-haired Whippets, Silken Windhounds, and mutts that might be derived from these breeds.

Animals can absorb ivermectin through oral or topical exposures as well as via injection. Symptoms arise when the drug is present in the body at high enough concentrations that it crosses the blood-brain barrier and adversely affects neurologic function. Typical signs include:

  • dilated pupils
  • unsteadiness when walking
  • mental dullness
  • drooling
  • vomiting
  • blindness
  • tremors
  • seizures
  • coma

Treatment for an overdose of ivermectin is essentially symptomatic and supportive. If the poisoning is caught early enough, decontamination is helpful (e.g., washing pets after topical exposure or inducing vomiting and/or activated charcoal administration within a few hours of ingestion). Intravenous fluid therapy, endotracheal intubation, mechanical ventilation, extensive nursing care, seizure control, application of eye lubricants if the patient cannot blink, and nutritional support may all also be necessary. In some cases, intravenous lipid emulsion therapy, which is a new but promising option for certain types of poisoning, might be worth considering.

A pet’s prognosis can be quite good if aggressive treatment is initiated in a timely manner, but because severe cases of ivermectin overdose often require several weeks of therapy, the expense is often prohibitive …  as was the unfortunate case with my clients who chose to euthanize the last puppy in what had been their much anticipated litter.


Dosage to treat mange

Please ask for and follow your vet’s instructions when you use Neomec (Ivermectin). Also read the packaging. (Update Dec 2018 – see below)

Many people give one Neomec tablet per week for four weeks. Some people also give a teaspoon of a liver protector, such as Liv-52, at the same time.

In addition, use Amitraz bath. This is an insecticide. Dilute it in water (follow the instructions on the packet) and put it on the affected skin twice per week for 4 – 6 weeks. One vial of Amitraz costs about Rs50 (in late 2016).

A packet of 5 Neomec tablets costs about Rs60 (in late 2016), and a packet of 10 tablets costs about Rs100.

How to administer a Neomec tablet   You can try putting the tablet in the dog’s mouth, but it’s safer to you (and easier) to either crumble the tablet into the dog’s food or hide the tablet inside a sandesh or other treat. An alternative is to use an injection – ask your vet which which is best.


Update (December 2018)

At last, the manufacturers of Neomec have added an information leaflet inside the packet. Here are photos of the recommended dosages, plus contraindications. (Note: Ectoparasites are parasites on the outside of the body, and endoparasites are those inside the body.) If you’re not sure about a meaning, please check with a vet before you give the dog this medicine. Click on an image to enlarge.



The following extracts are copied from the information leaflet produced by Neomec manufacturer, Intas Pharma:



For dogs suffering from mixed parasictic infection, for treatment of ear mite infestation (Otodectes cynotis), scabies (caused by Demodex canis), prevention of heartworm disease (L3 and L4 larvae of Dirofilaria immitis), treatment of ticks infestation (caused by Rhipicephalus sanguineus), lice infestation and treatment of infections with gastrointestinal nemotodes (L4 larvae, immature and adults of Toxocara canis, Ancylostoma caninum and Uncinaria stenocephala, adults of Toxascaris leonina and Trichuris vulpis).



For Endoparasites:

Nematodes at 0.2 mg/kg body weight as a single dose

Whipworms at 0.2 mg/kg body weight once daily for 3 days

Microfilia of Heartworm at 0.05 mg/kg body weight once a month


For Ectoparasites

Sarcoptes, Otodectes and Cheyletiella Mites at 0.2-0.25 mg/kg body weight twice in a week till clinical and parasitic cure

Demodex Mites at 0.3-0.6 mg/kg body weight until 2 negative skin scraping tests

Ticks at 0.2 mg/kg body weight as a single dose

Lice at 0.2 mg/kg body weight at weekly interval



Ivermectin is not recommended for use in puppies less than 6 weeks of age. Ivermectin should not be used in Collies or Collie-mix breeds at the doses specified for treating microfilaria or other parasites unless alternative therapies are unavailable. This is due to a more permeable blood-brain barrier to the drug or drug accumulation in the central nervous system. At the dosage recommended for heartworm prophylaxis, it is generally believed that the drug is safe to use in Collies at the dose of 0.05 mg/kg body weight.


Animal Safety and Adverse Reactions

Although Ivermectin is safe at 10 times the recommended dose for canines, the reactions may be observed transiently in a few animals, viz depression, lethargy, vomiting, diarrhoea, mydrisasis, ataxia, staggering, convulsions and hypersalivation. Dogs that are accidentally overdosed develop signs of acute toxicity (central nervous system effects, GI, Cardiovascular) and should be advocated with supportive and symptomatic therapy. Emptying the gut should be undertaken to avoid further drug absorption.


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