IVERMECTIN TOXICITY
This toxic reaction occurs especially in dogs that are genetically hypersensitive to ivermectin, an anti-parasite medication most commonly used for heartworm prevention, or to treat ear and hair mites, which can lead to mange. Ivermectin prevents or kills parasites by causing neurological damage to the parasite, resulting in paralysis and death for the parasite. But dogs genetically sensitive to the medication have an anomaly that allows the ivermectin to pass the dog’s blood-brain barrier and into its central nervous system, which can be lethal for the animal.
About Ivermectin »
While the sensitivity to this type of medication is not always guaranteed, the following breeds are most likely to be affected (although not every “sensitive” animal in the breed is affected):
- Old English Sheepdog
- English Sheepdog
- Shetland Sheepdog (Sheltie)
- Australian Shepherd
- German Shepherd
- Long-haired Whippet
- Silken Windhound
- Skye Terrier
- Collie
Washington State University Veterinary School developed a DNA test for a mutant gene which produces adverse reaction to ivermectin and other medications in some dogs. They have discovered that 75% of Collies, 25% of Border Collies, 8% of Old English Sheep dogs, mixed dogs of these breeds, plus other breeds have this mutant gene.
It is also seen in mixed-breed dogs, older dogs that have experienced a blow to the head, puppies, dogs that have overdosed on similar types of drugs, or other central nervous system diseases that affects the blood-brain barrier. Treating dogs that are susceptible to ivermectin toxicity with parasitic medication should be only be done under a veterinarian’s supervision and with great caution.
For breeds predisposed to the disease, an autosomal recessive trait (MDR-1) gene has been identified that causes a defect in the p-glycoprotein multidrug transporter to the blood brain barrier. This allows the ivermectin to pass into the brain at low dosages thus causing toxicity. This trait may also cause toxicity from other related drugs and should also be avoided or used in lower doses in susceptible breeds.
Toxicity can occur in cats, although it is uncommon.
SYMPTOMS
Symptoms for the dog may be acute or mild. Acute signs will become apparent within 4 to 12 hours of the drug’s administration. In mild cases, symptoms will occur between 48 to 96 hours after your dog has been treated. Such symptoms include:
- Lethargy
- Depression
- Drooling
- Vomiting
- Dilation of the pupil
- Loss of appetite (anorexia)
- Difficulty controlling voluntary movement
- Disorientation
- Tremors/Seizures
- Inability to stand
- Blindness
- Slow heartbeat
- Respiratory distress
- Coma
TREATMENT
Unfortunately, ivermectin toxicity cannot be reversed. Therefore, it is best to make your pet comfortable and treat the symptoms to the best of your ability. If exposure has occurred within the past four to six hours, induce vomiting and/or administer activated charcoal for the purposes of minimizing absorption. Be on the lookout for signs of secondary complications.
Some or all of the following measures may also be recommended by your veterinarian:
- Intravenous fluid therapy
- Keeping electrolytes in balance
- Intravenous nutritional support
- Turn the dog over frequently
- Appropriate bedding
- Physical therapy
- Ocular lubricants
- Ventilator in case of respiratory distress
- Heat support if body temperature is low
- Fans if body temperature is high
- If your dog can not stand up, urinary catheters may be needed
- Medication for seizures if appropriate
Much will depend on the severity of the dog’s reaction, along with its initial overall health. It may take several weeks of dedicated care before the dog fully recovers.
PREVENTION
There is a test available to check sensitivity to ivermectin. If your dog is one of the breeds that is prone to ivermectin toxicity, you might consider testing for it. If you decide not to have the testing done, be cautious about using ivermectin to prevent heartworm disease or for the treatment of mites.
In dogs with MDR 1 gene mutation, the following drugs should be avoided or used with caution:
- Ivermectin
- Selamectin
- Milbemycin
- Moxidectin
- Loperamide
- Acepromazine
- Butorphanol
- Vincristine
- Vinblastine
- Doxorubicin
WHY TELL YOU ALL THIS?
I include all this scary stuff so you know what can go wrong when using ivermectin on your own to treat your pets. It’s the same ingredient used in the popular heartworm meds you can buy for cats and dogs, but I know someone whose dog died when she administered Zimecterin Gold, a horse wormer, to her dogs. I don’t know the particulars in her case — what breed her dog was, how much she dosed, etc. I offer this info so you know what can go wrong and are as informed as possible before going this route. I assume no responsibility. Zimecterin Gold contains ivermectin and praziquantel. The praziquantel kills tapeworms. I have used this product for several years on my cats and dogs with no ill effects (knock on wood). My dogs are mutts. But be aware of the hazards if you have any of the breeds mentioned above. Having several cats and dogs, this is a more affordable alternative for me. There are several generic versions of heartworm preventative on the market. I used to order them from PetShed out of Australia. That worked fine, too. However, I have a number of cats and dogs and even the generic version became quite expensive.
Zemecterin Gold comes in an oversized syringe with a dosage appropriate for horses. The plunger on the syringe is marked at 50 lb intervals. This is how I determine the appropriate dosage. One syringe treats approximately 1300 pounds and costs about $15.
You can also buy the cattle version of just plain 1% ivomec (without the praziquantel), but it requires a larger dosage ivermectin (1/10 of 1 cc per 10 pounds) and it tastes really nasty. So you need to mix it in something like orange juice or yogurt.
Overview
- Parasitic diseases are common in animals. Parasites can affect the skin, ears, stomach and intestines, and the internal organs including the heart, lungs and liver. Several drugs have been developed to kill or prevent parasites such as fleas, ticks, mites and worms. Ivermectin and related drugs are among the most effective of these.
- Ivermectin is a parasite control drug. Ivermectin causes neurologic damage to the parasite, resulting in paralysis and death.
- Ivermectin has been used to prevent parasite infections, as with heartworm prevention, and to treat infections, as with ear mites.
Ivermectin as a Heartworm Preventive Medication in Dogs
Ivermectin is approved by the United States Food and Drug Administration (FDA) to prevent heartworm infections in dogs. Products containing Ivermectin are normally administered monthly for heartworm prevention and include medications such as Heartgard®, Iverhart®, Tri-Heart® and many other generic ivermectin-based heartworm preventive medications.
When used as a heartworm preventive medicine, ivermectin is used at much lower dosages than when used for other purposes. When used at the lower heartworm prevention dosages, ivermectin has a much lower potential for side effects than when used at higher dosages and this is the reason that ivermectin is approved for use as a heartworm preventive medication but must be used off-label (in a fashion not approved by the FDA) for many other purposes.
Read more at Suite101: Ivermectin for Dogs: Usages, Safety and Side Effects of Ivermectin in Dogs
Brand Names and Other Names
- This drug is registered for use in animals only.
- Human formulations: None
- Veterinary formulations: Ivomec® (Merial), Zimectrin® (Farnam), Eqvalan® (Merial), Heartgard® (Merial), Iverhart® (Virbac) and various generic preparations
Uses of Ivermectin
- Ivermectin is used to control skin parasites, gastrointestinal parasites and parasites within the bloodstream.
- Ivermectin prevents development of heartworm disease in dogs and cats.
- Ivermectin can be used in an extra-label manner to kill microfilaria (microscopic offspring) in heartworm infected dogs.
- Ivermectin is not effective against tapeworms and liver flukes.
How Ivermectin Is Supplied
- Ivermectin is available in 10 mg/ml and 2.7 mg/ml injectable form; 0.153 percent and 1.87 percent paste form; 10 mg/ml liquid oral form and 68 mcg, 136 mcg and 272 mcg tablets.
- Heartgard Plus® and Iverhart® are available in various concentrations of ivermectin combined with pyrantel pamoate.
Dosing Information
- Medication should never be administered without first consulting your veterinarian. The dose for ivermectin varies from species to species and also depends on the intent of treatment. General dosing guidelines follow.
- For dogs: Dose is 0.0015 to 0.003 mg per pound (0.003 to 0.006 mg/kg) once a month for heartworm prevention; 0.15 mg per pound (0.3 mg/kg) once, then repeat in 14 days for skin parasites; and 0.1 mg per pound (0.2 mg/kg) once for gastrointestinal parasites.
- For cats: Dose is 0.012 mg per pound (0.024 mg/kg) once monthly for heartworm prevention.
- The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your pet feels better, the entire treatment plan should be completed to prevent relapse or prevent the development of resistance.
Posted on December 28th, 2009 by isak
Filed under: Cats, Dogs, Pet Illnesses, Pet Meds/Vaccinations
My Husband and I have breed dogs for close to 20 years, and this is the first time using this Medication on our 4 month old Mini Dachshunds. He gave them the dose that seemed to be correct. The Next day, One was near death and the other two were very sick as well. This medication, should not be used on dogs. One of mine died last night, and one seems to be blind. It is not worth the effect this could have on your dog and you as the owner. We of course have decide against using this medication on any of our pets. My husband spoke to a feed store owner today, and He too agrees. He also stated that many people purchase this to give to their Beagles. Please use Zimecterin Gold only on horses. This medication is no joke and causes a sad slow, death for the animals.
I have a 5 months old Pitbull/German Shepard mix. He was diagnosed with Demadex Mange and was prescribed Ivermectin. He was on a low dose at first but then they increased it. After they did that we noticed his pupils dilated and the next day after another dose he became very ill. He is in the hospital now and he’s stable, but I am worried he will have permanent damage. I also question why the vet didn’t think to test him or take precautions since he has one of the sensitive breeds in him.
My 5 month old puppy was diagnosed with demodetic mange. The vet gave him ivamec 2cc every day. The second day i noticed that his back legs began to get wobbly. Does he have ivamec posioning and if so what should i do and is there any thing else to cure demodectic mange?
I just adopted a lab/retriever mix from a local shelter 10 days ago. She has been put on ivomec teo days before we got her as a treatment for demodectic mange. She has spent the last two days in the vet hospital on IV ans steriod drip. She was falling over, deeply depressed, swollen eyes, etc. They also diagnosed her as heartworm positive, which I was told she didn’t have upon adoption. Poor baby. She’s only 2 years old. Will she ever get better? I fear not. Do dogs recover from this toxicity?
Our 12 yr old very healthy male golden retriever had a severe adverse reaction to Heartgard Plus three days ago. He had all the symptoms listed above (except seizure, coma, and death… so far anyway). He’s taken this stuff for years with only getting nausea in the past. He vomited within an hour but still (today) has dilated pupils, fear & paranoia, difficulty standing, and staggers like a drunken sailor. The vet only gave him some anti-nausea pills. She seemed incredulous that this was the cause. I can assure you, I watch my dogs very closely and this reaction was caused by the Heartgard. I can coax him to drink and eat boiled chicken but mostly he’s just laying around looking miserable (POOR BABY!).
So… it’s not just collies and it’s not just “high” doses that can cause problems. I just hope he recovers from this because I can’t find anything (online or from the vet) that talks about possible long term damage.
It is to notice Finnish Lapinkoiras can carry the MDR1 lethal mutation too. Recently one dog of this breed died in Canada from ivermectin.
I have a poodle schnauzer cross, Rosey, that had her 18th birthday in June. She averages 18-20lbs weight. I have been giving her 2/10 ml 1% IVOMEC [injectable-but dosed orally in dogs] since I adopted her at 6 months of age. In our South Central U.S. location I give this every 30 days year round. I was a veterinary assistant at the time I acquired old Rosey. This was the dose recommended by the very good vet that I worked for. I had several dogs at the time and it was most economical for me. I have never used anything else for parasite control on any of my dogs. They have all stayed healthy and lived long lives on it. This includes many purebreds as well as my favorite mutts. [no collies of course, but I did have one Aussie that was on it with no problems]. I now have two Jack Russell Terrier / Min Pin mix pups that are 9 months old which I have started on the IVOMEC. Rosey plays with them and they are all a lively bunch. We also have an Anatolian Shepherd Dog which weighs 110 lbs. He is on the 1% IVOMEC and gets 1 full ml every month. No ill effects for him either. Of course dogs should be heartworm free before begining this high a dosage, but keep in mind that too low a dosage is not 100% effective for heartworm prevention and does nothing for intestinal worms either. The dose in Heartguard is NOT effective on other [intestinal] parasites. Old Rosey has NEVER had any intestinal parasites and has had a clean [occult] heartworm test every year of her life as well as clean fecal exams. I attribute this, thanks to the IVOMEC, and her hearty mix-breed constitution to her longevity. I expect the old gal has several more good years in her yet!
This is great information shared above and has enlightened me a great deal with regards to a situation I am going through with my dog right now. A few days ago I gave my dog her monthly dosage of HeartGuard a few days ago and within 30 minutes her rear legs were paralyzed. One more then the other. We ruhed her to the hospital and then to a Neurologist who tested her with an xray, catscan, myleogram, spinal tap, etc…everything came back relatively normal with the exception of a little swelling in the L3/L4 area of the spinal cord. We have her home no and are treating her with Prednezone daily. We feel very strong that this paralysis is attributed to the HeartGuard. My dog also had a liver shunt that corrected a little over a year ago and has not taken HeartGuard since that time due to the fact we lived in Las Vegas for a while and wasn’t necessary. 2 questions:
1. Why is my Neurologist insistent that this wasn’t the cause of her partial paralysis?
2. What are the recommended next steps?
Thank you in advance for your feedback.
Derek
I have been using the 8gm/l ivomec for many, many years. Originally the vet told me to use 1ml per 10 kg (sorry I am from Ossie) and said it was a fairly strong solution which meant that if I was not accurate in my dates of administration, it would not matter, even if it was a couple of weeks late. The vet used to do a lot of volunteer animal relief work overseas where there was a crisis due to flooding etc. He told me that he used to take the ivomec himself to prevent getting stomach bugs in these under developed areas and he never got food poising or anything similar.
our 2 month old mixed breed puppy overdosed with ivermectin.
it was an over-calculation of the dosage for a puppy his size. an understood accident and human-error but still resulted in a very sad outcome.
we saw him slowly loss his coordination and mobility.
he is now paralyzed – he can’t stand up – he totally lost mobility.
we’re deeply saddened by what happened to our little baby.
my question is: is it still possible for him to recover from his paralysis? what are the chances that he’d be normal again?
many thanks.
Your dosage for 1% Ivomec for heartworm prevention is incorrect. 1% Ivomec contains 10 mg/ml of ivermectin, or 10,000 mcg/ml. Ivermectin dosage for heartworm prevention in dogs is 2.73 mcg to 5.5 mcg per pound. Therefore a 100 pound dog would need between 273 and 550 micrograms of ivermectin. If you gave the 100 pound dog 1/10 of one cc for every 10 pounds, you would be giving him 10,000 micrograms. If you gave the 100 pound dog 1/10 of a cc you would be giving him 1,000 micrograms. 1/20 of a ml would give the 100 pound dog 550 mcg, but you can’t measure 1/20 ml accurately. To verify the information I am giving, look at a pack of heartworm preventative tablets to see how much ivermectin is in them. The 51 to 100 pound pack has 272 mcg in each tablet. That’s 2.72 mcg for the 100 pound dog. Yes, ivermectin is used at higher doses offlabel for other types of parasites, mange, etc. but not in collies and other breeds which might carry the gene. I am curious as to where you obtained your dosing recommendation.
Reference: See footnote no. 4 at the bottom of this article:
http://web.archive.org/web/20061104194714/http://www.heartwormsociety.org/katrina.htm
[...] 1 dose and she seems ok and then I found this should I stop using it on Bella? I'm worried now Ivermectin Poisoning from Parasite Prevention Drugs in Dogs | beingstray.com __________________ [...]
Jo–
The dosage came from several breeders and a few vets based on the protocol they have been using/recommending for years. I have used it for several years on my own dogs as well. I do not use it in the winter months so the dogs do not build up a resistance to the ivermectin. From what I have read, it is not necessary to administer heartworm preventative during non-mosquito season. I have also read that Heartgard is not necessarily a point of reference.
You lost me in the middle of your math with this: If you gave the 100 pound dog 1/10 of one cc for every 10 pounds, you would be giving him 10,000 micrograms. If you gave the 100 pound dog 1/10 of a cc you would be giving him 1,000 micrograms.
There seems to be a lot of latitude with the ivermectin dosage, however why administer more than is required. So I will do some new research based on new references I have and make any necessary adjustments. Many thanks for the info.
I don’t know about overcoming the paralysis. Given his young age, it seems that he might have the strength and vigor to overcome some of it. I am so sorry this has happened to you. Do you know what the dosage you used was and how you administered it so we can warn others? Your comment is a few weeks old (sorry. I’ve been away attending an ailing senior dog.). Has there been any change/improvement to his condition?
What breed of dog do you have? Is she one of the breeds that is overly sensitive to ivermectin?
Here’s to Rosey… and many more healthy, happy years! And to her playmates as well. Do you mix the 1% with anything to disguise the taste?
I am so sorry to hear about your boy. I hope he recovers fully. Let us know.
Your vet can best tell you, but many dogs overcome this.
Dogs can sometimes have a reaction to ivermectin if they are heartworm positive or they can have a bad reaction to the ivermectin itself for various reasons. Right now, your vet is the best source of info on this.
Best wishes, and please let me know how she does. Prayers to you both! And think positive! Think of many long years together once you get this behind you!