The Collie breed
along with a few other breeds, are carriers of a genetic mutation in the MDR1
gene. This protein made from this gene
is responsible for transporting drugs across the blood-brain barrier. A mutation
in this gene enables some drugs to accumulate in the brain in abnormally high
amounts possibly resulting in an overdose and death of the dog. The following link lists breeds known to have
MDR1 mutations and includes the frequency of the mutation https://www.vgl.ucdavis.edu/cghg/mdr1b.php About 75% of all Collies are affected in
some way either being carriers of the mutation or pure mutants. Dogs with two copies of the mutation (25% of Collies)
are highly susceptible to overdosing from some drugs.
A classic saying
taught to veterinarians during their schooling is, “white feet, don’t
treat”. The sentence typically refers to
the use of Ivermectin. The number of
drugs found to be affected by the MDR1 mutation has expanded past Ivermectin ( vcpl.vetmed.wsu.edu/problems-drugs
). Included in the list are many de-wormers
and anti parasitics (Ivermectin, Flagyl), Loperimide (Imodium® - anti-diarrhea),
Morphine, Buprenorphine, Fentanyl and Acepromizine (pain
killers and pre-anesthetics), as well as many chemotherapy agents.
Recently I had an
encounter with a newly graduated veterinarian.
She quoted to me the, “white feet, don’t treat” saying and also told the
pup, “No Ivermectin for you.” As I was
casually mentioned that many other drugs were now included on the list, she was
about to give the pup a dose of de-wormer (we had forgotten to bring in a poop
sample). I stopped her and asked her
what were the active ingredients in that wormer and she didn’t know. Not
knowing the MDR1 status of my pup and having my handy list of drugs known to
cause problems in MDR1 mutants with me, I stopped her until I had an answer.
In summary, it
may not only be useful, it may be life saving for our dogs, for us to know the
dog’s MDR1 status of our Collies and familiarize ourselves with the list of
harmful drugs if our dogs have the mutation.
We should not rely on our veterinarians to be encyclopedias of all
breeds and drugs and we should be able to have discussions with our
veterinarians about their drug choices for our dogs.
Below are links for
MDR1 Testing. Testing is as simple as mailing in a cheek swab. At
this writing the last link had the best pricing. Two out of my three
Collies are carriers and one tested to be a mutant. The mutant happens to be the pup mentioned
above in the de-worming example.
MDR1 Testing
The drugs listed below put your MDR1 dog at risk.
Class A
Do NOT use these drugs with the MDR1 gene defect:
Ivermectine substances "Anti parasites": (Diapec®,
Ecomectin®, Equimax®, Eqvalan®, Ivomec®, Noromectin®, Paramectin®, Qualimec®,
Sumex®, Virbamec®)
Doramectine substances "Anti parasites": (Dectomax®
)
Loperamide substances "ant diarrheal ": (Imodium®)
Moxidectine substances "Anti Parasites"
(Cydectin®, Equest®) (Flagyl )
Class B
Use only under close supervision of Veternarian:
Cytostatics "Chemotherapy": (Vinblastine,
Vincristine, Doxorubicine, Paclitaxel, Docetaxel, Methotrexat, Vincristine)
Immunosuppressive: (Cyclosporine A)
Heart glycosides: (Digoxine, Methyldigoxine)
Opioids: (Morphium) Antiarrhythmics: (Verapamil,
Diltiazem, Chinidine)
Antiemetics (Ondansetron, Domperidon, Metoclopramide
)
Antibiotics (Sparfloxacin, Grepafloxacin,
Erythromycin)
Antihistamin (Ebastin) Glucocorticoid (Dexamethason)
Acepromazine (tranquilizer and pre-anesthetic agent)
*
Butorphanol "analgesic and pre-anesthetic
agent" *
Other drugs: Etoposide, Mitoxantrone, Ondansetron,
Paclitaxel, Rifampicin
Class C
Can be used only in the permitted application form and dose:
Selamectin (Stronghold®), Milbemax® and
Advocate®
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