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Ivermectin

Vets have a saying regarding Ivermectin:
"White feet? Don’t treat!"

We had a sad situation occur with a friends Lab last night (9-14-09). After receiving an overdose of Ivermectin, the dog presented symptoms of poisoning and died hours later.

There is NO ANTIDOTE for IVERMECTIN POISONING. Your dog must not have heartworms prior to administering the Ivermectin and the correct dosage is extremely important! 

The Ivermectin used is for cattle to control parasites and it is the INJECTIBLE type. It is a 1% injectible cattle wormer with the trade name of Ivomec ™. This is given orally (by mouth) to your dog, it is not to be injected.

It is important that you get a syringe (without the needle) which shows amounts less than a full cc so you can give the exact amount needed. Many drugstores will give you one syringe without a needle if you tell them it is for administering a medication to your dog.

Your dog must be heartworm free. He must NOT have heartworms prior to receiving this medication. If you are not sure but choose to administer the medication anyway, only give 1/4 of the suggested dosage. Our friend did not do that, he gave a full dose without knowing if his dog had heartworms or not.

If you think there is ANY chance your dog may have heartworms, only give 1/4cc (0.25 ml) of 1cc (1 ml).

If there is no indication of poisoning, treat again with the same amount 1/4 cc, two weeks later.

A dog that is HEARTWORM FREE and weighs 100lbs would normally receive 1cc (1ml) of Ivermectin.

If you have given your dog this medication and they present with signs of Ivermectin toxicity, you must help him to vomit up as much as possible by using hydrogen peroxide. One teaspoon of hydrogen peroxide per 10 lbs (ten pounds) of body weight can induce vomiting in a little as five minutes. This is only effective if it has been less than an hour after giving the Ivermectin.

DO NOT induce vomiting in a dog which is having trouble breathing. It is easiest to administer the peroxide using a syringe but if you do not have one handy, try a baby syringe, a turkey baster, a snow cone cup, you get the idea, anything which will safely get the peroxide into your dogs mouth. Squirt the peroxide into the area between the cheek and gums of your dog so as not to choke him by accidentally putting it into his windpipe.

If it has been more than several hours since treatment, Do NOT induce vomiting as it is too late for this treatment to help. If has been less than an hour, you can give ACTIVATED CHARCOAL  to absorb any toxins that have made it past the stomach and it may be removed in his stool.

This activated charcoal is NOT the kind used for barbecuing. It is the charcoal found in the vitamin aisle of your grocery store. 

  • Activated charcoal is estimated to reduce absorption of poisonous substances up to 60%.
  • It works by adsorbing chemicals, thus reducing their toxicity (poisonous nature), through the entire length of the stomach and small and large intestines (GI tract).
  • Activated charcoal itself is a fine, black powder that is odorless, tasteless, and nontoxic.
  • Activated charcoal is often given after the stomach is pumped (gastric lavage). Gastric lavage is only effective immediately after swallowing a toxic substance (within about one-half hour) and does not have effects that reach beyond the stomach as activated charcoal does.
  • Activated charcoal is often combined with sorbitol (a substance that stimulates the bowels to move, like a laxative) to shorten the amount of time to move through the system and reduce the possibility of constipation. However, to avoid adverse effects, sorbitol is not given with every dose of activated charcoal.

Ivermectin should never be used in Collies, Shetland Sheepdogs, Old English Sheepdogs, Australian Shepherds and sometimes other herding dogs.

Ivermectin is a anti-parasitic medication and is effective against most common intestinal worms (except tapeworms), most mites, and some lice.

While normally used to treat animals, it is also prescribed to humans to treat infections of Strongyloides stercoralis and onchocerciasis (river blindness) in Africa. It is sold under brand names Stromectol® in the United States and Mectizan® in Canada.

The white feet saying relates to the gene {si~si} (sucrase-isomaltase) which is the "Irish spotting white" allele. It can be found in many breeds, and in many species, but in dogs and cats, when mixed with other white factor genes, it becomes what is called a "double lethal". That term does not mean it kills the animal, it is just a term for an animal that has inherited two copies of the same dominant gene, and sometimes causes health problems and sensitivities to medications and vaccines.

Old English Sheepdogs, and Ragdoll cats are most widely known for these anomalies because of breeders attempting to control the si~si gene to create specific coat patterns. Collies with Ivermectin sensitivity have been found to have a mutant gene for what is called the "P-glycoprotein." The P-glycoprotein has been studied largely because overexpression of this protein (i.e., having more of it than normal) results poor function of chemotherapy drugs in the treatment of cancer. The P-glycoprotein appears to be involved in keeping drugs out of certain body tissues. Having excess P-glycoprotein keeps chemotherapy drugs from reaching the tumor; having a mutant/non-functional protein fails to keep medications like Ivermectin out of the central nervous system.

In other words, Collies (and their cousins: Old English Sheepdogs, Shetland Sheepdogs, Australian Shepherds, etc.) have less P-glycoprotein than normal. Having less P-glycoprotein means certain drugs gain access to protected body tissues more readily. This phenomenon is responsible not only for Ivermectin toxicity in sensitive breeds but also Loperamide toxicity. Loperamide is the drug in Imodium. Approximately 35% of Collies appear affected by this condition. Approximately 35% of Collies appear affected by this condition.  It is probably best to avoid Loperamide in Collies and their relatives

Source: The Washington State University Veterinary School website:

 It is well known that Collies and related breeds can have adverse reactions to drugs such as Ivermectin, Loperamide (Imodium®), and others. It was previously unknown why some individual dogs were sensitive and others were not.

Advances in molecular biology at the Veterinary Clinical Pharmacology Laboratory at Washington State University's College of Veterinary Medicine have led to the discovery of the cause of multi-drug sensitivity in affected dogs.

The problem is due to a mutation in the multi-drug resistance gene (MDR1). This gene encodes a protein, P-glycoprotein, that is responsible for pumping many drugs and other toxins out of the brain. Dogs with the mutant gene can not pump some drugs out of the brain as a normal dog would, which may result in abnormal neurologic signs. The result may be an illness requiring an extended hospital stay--or even death.

A test has recently been developed at Washington State University to screen for the presence of the mutant gene*. Instead of avoiding drugs such as Ivermectin in known susceptible breeds, veterinarians can now determine if a dog is normal, in which case the drug can be administered or abnormal, in which case an alternative treatment can be given. 

 Owners and breeders can submit samples for testing. All that is needed for the test is a cheek brush sample that can be obtained by the owner and sent by mail for analysis.

Affected Breeds

Approximately 3 of every 4 Collies in the United States have the mutant MDR1 gene. The frequency is about the same in France and Australia, so it is likely that most Collies worldwide have the mutation. The MDR1 mutation has also been found in Shetland Sheepdogs (Shelties). Australian Shepherds, Old English Sheepdogs, German Shepherds, Long-haired Whippets, Silken Windhounds, and a variety of mixed breed dogs.

The only way to know if an individual dog has the mutant MDR1 gene is to have the dog tested. As more dogs are tested, more breeds will probably be added to the list of affected breeds.

Ivermectin is not approved to be used in this manner.  So your veterinarian should let you know this prior to getting your permission to utilize Ivermectin therapy in the treatment of scabies (mange) in dogs and cats.

You can retain some confidence to know that it is in common usage, and has been for a number of years, for the treatment of scabies (mange) in pets.  It simply has not been tested by the manufacturer and approved by the FDA to be used in this manner. You are on your own, you and your veterinarian, in the decision-making arena regarding whether or not to use it to treat sarcoptic mites. 

Your alternative is to use insecticide dips and sprays.  Administering the correct dose of ivermactin is very important since an incorrect dosage could cause your dog to have a very serious and even fatal reaction.

All pets in contact with an affected animal should be treated since there can be asymptomatic carriers (they have the disorder but aren’t showing any signs of disease) of the sarcoptic mites.