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Info on Multi Drug Sensitivity
Info on the Australian Shepherd and the MDR1
DNA test now available
DNA testing is now available to determine each dogs genetic make up. See contact info at the bottom.
|From the Washington State University
Veterinary Clinical Pharmacology laboratory Website:
Evaluation of the risks determined by DNA testing
These dogs do not carry the mutation, and will not pass on the mutation to
their offspring. These dogs would not be expected to experience unexpected
adverse drug reactions to normal doses of ivermectin, loperamide (Imodium®),
and some anticancer drugs.
2007 National Specialty
Health & Genetics Events:
Some breeds of dogs are more sensitive to certain drugs compared to other breeds. For example, Collies, Australian Shepherds and several other breeds can have adverse reactions to drugs such as ivermectin, loperamide (Imodium®), and others.
Advances in molecular biology 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. Approximately 33% of Australian Shepherds have either one or two copies of the mutated MDR1 gene.
A test has been developed to screen for the presence of the mutant gene. Instead of simply avoiding drugs such as ivermectin, you can now determine whether or not your dog carries the mutated version of the gene and, if it does, whether it has one copy or two. Dogs that do not have the mutation at all may safely receive the listed drugs. Dogs with two copies should not have any of those drugs. If only one copy is present, some of the drugs may cause a reaction, depending on dosage.
Alternate medications are available for all the drugs identified thus far as MDR1 reactive. All that is needed for the test is a cheek brush sample that can be obtained and sent by mail for analysis.
There are many different types of drugs that have been reported to cause problems ranging from over-the-counter antidiarrheal agents like Imodium® to antiparasitic and chemotherapy agents. It is likely this list will grow to include more drugs as our research progresses.
Drugs that have been documented, or are strongly suspected to cause problems in dogs with the MDR1 mutation:
following drugs may potentially cause problems when given to dogs that
have the mutation.
information courtesy Washington State University College of Veterinary