Ivermectin for Dogs and Cats

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Ivermectin for dogs and cats is an antiparasitic drug that is used for various infections involving roundworms, threadworms, and other parasites. When introduced in the mid-1980s, ivermectin was the only broad-spectrum anti-parasite medication of its kind. 

Additionally, the medication is used to address lung parasite infections, intestinal parasites, mites, mange, etc. Ivermectin for heartworm prevention is among the many uses of this drug.

Ivermectin is effective against most common intestinal worms, with the exception of tapeworms, most mites, and some lice. This product is not effective against fleas, ticks, flies, or flukes. It is active against larvae, killing them quickly, but not efficient against adult worms, though it can be believed that it can decrease their lifespans.

Ivermectin is given monthly for heartworm prevention, daily (or every other day) for demodectic mange treatment, and weekly (or bi-weekly) for most mites.

The most common applications are:

  • Monthly prevention of heartworm infection (formerly a daily pill).
  • Treatment of ear mites
  • Heartworm infections
  • Treatment of sarcoptic, notoedric, or demodectic mange.
  • Ivermectin for tapeworms 
  • Ivomec for dogs
  • Ivomec for cats

Ivermectin for dogs and cats has ‘off-label’ or ‘extra-label’ uses as well. For dogs, this would be for mites, intestinal parasites, and capillaria. However, for cats, it is used to treat scabies in addition to ear mites. Off-label or extra-label uses should only be used with a doctor’s explicit direction.

Ivermectin Side Effects

There are some side effects to watch out for when giving doses of ivermectin for dogs and cats.

Is Ivermectin Safe For Dogs?

There are some ivermectin side effects for dogs to watch out for. Dog side effects range from mild to acute. In mild cases, symptoms appear within 48 to 96 hours after your dog has been treated. Acute signs typically appear within 4 to 12 hours after taking a dose. Contact your veterinarian to report the following issues:

  • Vomiting or loss of appetite (or anorexia).
  • Difficulty controlling voluntary movement, inability to stand, or disorientation.
  • Drooling
  • Trembling, tremors, or seizures
  • Respiratory distress or difficulty breathing.
  • Slow heartbeat
  • Depression or lethargy
  • Dilation of the pupil or sudden blindness.
  • Coma

Ivermectin is usually well-tolerated by dogs, but it can cause serious neurological side effects at high doses. In such situations, ivermectin for dogs might cause a shock-like reaction in some dogs.

Is Ivermectin Safe For Cats?

There are some ivermectin side effects for cats to watch out for. These are typically brought on by toxicosis. Most animals recover completely within 2 to 4 weeks, and signs disappear within a few days. Contact your veterinarian to report the following issues:

  • Depression or weakness
  • Mydriasis
  • Blindness 
  • Recumbency or ataxia
  • Coma

Less common side effects in animals:

  • Tremors or seizures
  • Bradycardia
  • Sinus arrhythmia
  • Hyperthermia 

Ivermectin Precautions

The veterinarian should go over any precautions about ivermectin for dogs in general, and specific to the animal’s unique medical circumstances.

Ivermectin should be used with caution or not at all for the following situations:

  • Puppies younger than 6 weeks of age 
  • Kittens younger than 1-year-old
  • Dogs with a current positive heartworm test. 
  • Animals who are sensitive or allergic to anti-parasite medication toxicity.
  • Animals who are raised to produce dairy or meat products.
  • Turtles
  • Tortoises
  • Indigo snakes
  • Birds
  • Skinks

Some “white feet” canines are genetically sensitive to ivermectin for dogs. This is due to an anomaly that allows the medication to pass the dog’s blood-brain barrier, and enter its central nervous system. This creates a potentially lethal situation for the following breeds:

  • Old English Sheepdog
  • English Sheepdog
  • Shetland Sheepdog (Sheltie)
  • Australian Shepherd
  • German Shepherd
  • Long-haired Whippet
  • Silken Windhound
  • Skye Terrier
  • Collie 

Neurologic toxicity is a prevalent concern with the use of ivermectin for dogs (and other animals). This happens when the dosage is too high or for animals who carry the MDR1 genetic mutation. For this reason, veterinarians should tell their clients to contact them immediately if they notice signs of a coma, weakness, blindness, clumsiness, dilated pupils, trembling, excessive drooling, or mouth foaming. An animal pressing its head against a wall is also a sign of distress.


Ivermectin for dogs and cats is usually administered in pill form. For patients under 6 weeks of age, oral or injectable ivermectin is not recommended.

Handling instructions

Unless you are allergic to such medications, ivermectin for dogs should be safe to handle.  After touching the medication, hands must be washed prior to smoking or handling food. Wash your hands completely after handling the medication. Also, avoid contact with your eyes.

Ivermectin for Dogs Dosage

Oral ivermectin for dogs is usually administered by tablets in plain or chewable form.  Ivermectin dosage for dogs comes in units of 68, 136, or 272 mcg. 

Ivermectin for dogs dosing is 6 micrograms per kilogram of body weight. The dose is given orally once every 30 days for heartworm prevention.

As a cautionary measure, veterinarians may advise clients to begin with a low dose (50-100 mcg/kg), but then work up to a maintenance dose by increasing in increments of 50-100 mcg/kg.

This medication might also be combined with other deworming medications that include pyrantel, fenbendazole, or praziquantel.


Ivermectin for Cats Dosage

Cats are usually administered ivermectin by a chewable oral tablet. Ivermectin dosage for cats is dosed in units of 55 or 165 mcg.

How much ivermectin to give a cat depends on weight. Veterinarians will prescribe doses of 24 mcg per kilogram of body weight. As with ivermectin for dogs, the dose is given to cats is once by mouth every 30 days for heartworm prevention.

Overdose Cautions

Double dosing would be toxic to an animal. So, if a dose of ivermectin for dogs is missed, refrain from doubling up. Missed doses may also lead to negative side effects (after missing over 8 weeks in a row).

The main concern of ivermectin for dogs and cats is the potential for adverse effects from an overdose. Adverse effects might also present themselves after cessation of the medication. Your clients should watch for staggering, vomiting, diarrhea, depression, dilated pupils, agitation, vocalization, loss of appetite, tremors, blindness, head pressing in cats, etc.

Note: Veterinarians should advise clients of when they will be due back for heartworm retest. Get a complete list of medications the animal is on to ensure risk mitigation for drug interactions. Tell your client that they should check with you before changing pet foods.


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