Important Drug Info
Please read carefully (to order test sample, click on second link middle of page)

Multi-Drug Resistance Gene (MDR1)


Multi-Drug Resistance Gene, (MDR) codes for a protein that is responsible for protecting the brain by transporting potentially harmful chemicals away from the brain. In certain breeds, a mutation occurs in the MDR1 gene that causes sensitivity to Ivermectin, Loperamide, and a number of other drugs. Dogs with this mutation have a defect in the P-glycoprotein that is normally responsible for transporting certain drugs out of the brain. The defective protein inhibits the dog's ability to remove certain drugs from the brain, leading to a buildup of these toxins. As a result of the accumulation of toxins, the dog can show neurological symptoms, such as seizures, ataxia, or even death.

Dogs that are homozygous for the MDR1 gene (meaning that they have two copies of the mutation) will display a sensitivity to Ivermectin and other similiar drugs. These dogs will also always pass one copy of the mutation to all potential offspring. Dogs that are heterozygous (meaning they have only one copy of the mutation) can still react to these drugs at higher doses. Also, there is a 50% chance that a dog with one copy of the mutation will pass it on to any offspring.

There are many different types of drugs that have been reported to cause problems. The following is a list of some of the drugs:

Ivermectin (found in heartworm medications) Loperamide (Imodium over the counter antidiarrheal agent) Doxorubicin, Vincristine, Vinblastine (anticancer agents) Cyclosporin (immunosuppressive agent) Digoxin (heart drug) Acepromazine (tranquiliser) Butorphanol ("Bute" pain control).

The following drugs may also cause problems: Ondansetron, Domperidone, Paclitaxel, Mitoxantrone, Etoposide, Rifampicin, Quinidine, Morphine.

Sample Type:

Animal Genetics accepts buccal swab, blood, and dewclaw samples for testing. Sample collection kits are available and can be ordered at test now.

Test Is Relevant to the Following Breeds:

Australian Shepherd, Border collie, Collie, English shepherd, Longhaired Whippet, McNab Shepherd (McNab Border Collie), Old English Sheepdog, Shetland Sheepdog (Sheltie), Silken Windhound, Rough Collie, Smooth Collie, German Shepherd, Bobtail, American White Shepherd.


Animal Genetics offers DNA testing for multi-drug resistance gene (MDR1). The genetic test verifies the presenceof the recessive MDR1 gene and presents results as one of the following:



The dog carries two copies of the mutant gene and is homozygous for the MDR1 mutation. The dog will react to Ivermectin, or other listed drugs, and will always pass a copy of the mutated gene to its offspring.



Both the normal and mutant copies of the gene detected. Dog is a carrier for the MDR1 mutation, and can pass on a copy of the defective gene to its offspring 50% 0f the time.



Dog tested negative for the MDR gene mutation, and will not pass on the defective gene to its offspring.

To order a sample collection kit for the MDR1 Gene, please go to:

              Cost per sample is $55.00.


List of Drugs not to use on Aussies/Collies and other herding breeds

Never use an IVOMEC based product on an Aussie. It can kill them.

  • Abamectin Antiparasitic Agent
  •  Acepromazine Tranqualizers
  • Butorphanol Tartrate (Torbutrol, Torbugesic) Pain Control
  •  Cyclosporin Immunosuppressive agent
  • Cyclosporin A Immunosuppressive agent
  • Deramaxx
  •  dexamethasone, Steroids
  • Digoxin Heart drug
  • Domperidon Gastrointestinal Agents
  •  domperidone
  • doramectin
  • Doxorubicin Chemo drug
  •  Erythromycin Antibiotic
  •  etoposide
  •  Grepafloxacin Antibiotics
  •  Heartgaurd
  •  Hydrocortisone Steriods
  • Immodium Loperamide
  •  Ivermectin Antiparasitic Agent
  •  Kaopectate (some formulas)
  •  Loperamide (e.g. Immodium AD) Gastrointestinal Agents
  •  Macrocyclic Lactones Anti-helminthic pharameuticals that are P-glycoprotein substrates include the family of compounds
  • Milbemycin Oxime Antiparasitic Agent
  • mitoxantrone
  •  morphine
  •  Moxidectin Antiparasitic Agent
  • Ondansetron
  • Oxorubicin Anticancer agents
  • paclitaxel
  • PeptoBismol (some formulas)
  •  Pro Heart6
  • Quinidine
  • Revolution
  •  rifampicin
  • Rimadyl
  •  Selamectin Antiparasitic Agent
  • Substrates for P-glycoprotien
  • Tacrolimus Immunosuppressants
  • Vinblastine Chemo drug
  • Vinca Alkaloids Anticancer agents
  •  Vincristine Chemo drug
  • *Drugs that are P-glycoprotein substrates can build up dangerous levels in the brains of genetically sensitive Collies  

    This list may not be inclusive as new drugs are coming out all the time.

Jeffery Levy DVM PCH

Classical Veterinary Homeopathy


This parasite is a source of great anxiety among dog caretakers. (I don't believe that one "owns" a dog.) Thanks in large part to the scare tactics of many veterinarians in promoting preventive drugs, many people believe that contracting heartworms is the equivalent of a death sentence for their dogs. This is not true.

     I practiced for seven years in the Santa Cruz, California area, and treated many dogs with heartworms. The only dogs that developed symptoms of heart failure were those that were being vaccinated yearly, eating commercial dog food, and getting suppressive drug treatment for other symptoms, such as skin problems. My treatment, at that time, consisted of switching to a natural (that is, homemade) diet, stopping drug treatment whenever possible, and eliminating any chemical exposure, such as flea and tick poisons. I would usually prescribe hawthorn tincture as well. None of these dogs ever developed any symptoms of heart failure.

     I concluded from this that it was not the heartworms that caused disease, but the other factors that damaged the dogs' health to the point that they could no longer compensate for an otherwise tolerable parasite load. It is not really that different from the common intestinal roundworms, in that most dogs do not show any symptoms. Only a dog whose health is compromised is unable to tolerate a few worms. Furthermore, a truly healthy dog would not be susceptible to either type of worm in the first place.

     It seems to me that the real problem is that allopathic attitudes have instilled in many of us a fear of disease, fear of pathogens and parasites, fear of rabies, as if these are evil and malicious entities just waiting to lay waste to a naive and unprotected public.

     Disease is not caused by viruses or by bacteria or by heartworm-bearing mosquitoes. Disease comes from within, and one aspect of disease can be the susceptibility to various pathogens. So the best thing to do is to address those susceptibilities on the deepest possible level, so that the pathogens will no longer be a threat. Most importantly, don't buy into the fear.

  That having been said, there are practical considerations of risk versus benefit in considering heartworm prevention. The risk of a dog contracting heartworms is directly related to geographic location. In heavily infested areas the risk is higher, and the prospect of using a preventive drug more justifiable. Whatever you choose to do, a yearly blood test for heartworm microfilaria is important.

     There are basically three choices with regard to heartworm prevention: drugs, nosodes, or nothing.

     There are currently a variety of heartworm preventive drugs, most of which are given monthly. I don't like any of them due to their toxicity, the frequency of side effects, and their tendency to antidote homeopathic remedies. Incidentally, the once-a-month preventives should be given only every 6 weeks.

     The next option is the heartworm nosode. It has the advantage of at least not being a toxic drug. It has been in use it for over 10 years now, and I am reasonably confident that it is effective. It is certainly very safe. The biggest problem with the nosode is integrating it with homeopathic treatment. But at least it's less of a problem than with the drugs.

     The last option, and in my opinion the best, is to do nothing. That is to say, do nothing to specifically prevent heartworm, but rather to minimize the chances of infestation by helping your dog to be healthier, and thereby less susceptible. This means avoiding those things that are detrimental to health, feeding a high quality homemade diet, regular exercise, a healthy emotional environment, and, most of all, constitutional homeopathic treatment. Of course, this will not guarantee that your dog will not get heartworms, but, under these conditions, even the worst-case scenario isn't so terrible. If your dog were to get heartworms, s/he shouldn't develop any symptoms as a result.

     For what it's worth, I never gave my dog any type of heartworm preventive, even when we lived in the Santa Cruz area where heartworms were very prevalent. I tested him yearly, and he never had a problem.


Printed from Jeffrey Levy DVM PCH,
- © 2003, Jeffrey Levy, All Rights Reserved -