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The following
information is from an article published by the Washington State
University Veterinary Clinical Pharmacology Laboratory in
2007. You can read the entire article at www.vetmed.wsu.edu/depts-VCPL/
Please note:
The importance of this article is due to the high use of Heartguard
for controlling and preventing heartworm. Dogs with the mutant
MDR1 gene can have adverse reactions to the amount of ivermectin
in Heartguard. As a breeder, I recommend that you use an
alternative heartworm preventative such as Interceptor, which has a
lower dose of ivermectin and should not adversely affect dogs with
the mutant MDR1 gene. If you want to be sure whether or not
your dog has the mutant gene, gene testing can be done.
Contact your veterinarian for more
information.
It is well known that Collies and
related breeds can have adverse reactions to drugs such as
ivermectin, loperamide. It has been determined that these
breeds have this problem due to a mutation in the multi-drug
resistance gene (MDR1). This gene encodes a protein that is
respnsible for pumping many drugs out of the brain. Dogs with
the mutant gene cannot pump some drugs out of the brain as a normal
dog would. The result may be an illness requiring an extended
hospital stay or death.
This mutation has been found in
Collies, Shetland Sheepdogs, Australian Shepherds, Old English
Sheepdogs, German Shepherds, Long-haired Whippets, Silken
Windhounds, and a number of mixed breed
dogs.
There are many different types of
drugs that have been reported to cause problems. The
following is a current list of these drugs, however, please check
with the veterinary college for updated
lists.
Ivermectin (found in heartworm
medications)
Loperamide (Imodium over the
counter antidiarrheal agent)
Doxorubicin, Vincristine,
Vinblastine (anticancer agents)
Cyclosporin (immunosuppressive
agent)
Digoxin (heart
drug)
Acepromazine
(tranquilizer)
Butorphanol ("Bute" pain
control)
The following drugs may also cause
problems;
Ondansetron, Domperidone,
Paclitaxel, Mitoxantrone, Etoposide, Rifampicin, Quinidine,
Morphine
There are two solutions to the
affects of the MDR1 gene. You can have your dog tested
for the gene. If the dog is N/N you have no sensitivity,
otherwise it is recommended that you stay away from the above
drugs. The other is to simply avoid these drugs unless they
are necessary to the health of your dog, then test for the
gene.
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