MDR1 Multi-drug Resistance

What is the MDR1?

Multi-Drug Resistance 1 gene protects the brain by ensuring that any harmful chemical are transported AWAY from the brain.  This gene specifically codes for P-glycoprotein. If this specific gene is mutated, it will create a defective protein, and consequently, drugs will remain and build up in the brain to toxic levels. This dominant gene is inherited from the parents, whether the parent has two copies of the gene or only one copy. If neither parent has a copy of the mutated MDR1 gene, then the offspring will not have it either. 

Which breeds are affected?

Below is a list of breeds that are frequently affected by the MDR1 mutation, keep in mind that any mixed breeds you might find at the shelter with possible relation to the breeds in the list could also have the same problem.

Australian Shepherd

Border Collie

English Shepherd

Longhaired Whippet

McNab Shepherd

Old English Sheepdog

Shetland Sheepdog

Silken Windhound

Rough Collie

Smooth Collie

German Shepherd

American White Shepherd

English Shepherd

Attention! Even dogs that are unaffected by the MDR1 mutation may be exposed to toxic doses of this medication if they consume the feces of recently wormed cattle, horses, and sheep.

How can you find out if your dog has the MDR gen?

At the veterinary clinic your dog can be tested with either a cheek swab or a blood sample. The result you want to hear is Normal/Normal. 

If your dog gets this result you don’t have to worry about any drugs related to the MDR1 gene.

Normal/Mutant, or Mutant/Mutant should be considered sensitive to the drugs indicated in this list below:

Drugs that should be avoided: 

Acepromazine

Apomorphine

Butorphanol

Doramectin

Doxorubicin

Erythromycin

Ivermectin

Loperamide

Milbemycin

Moxidectin

Paclitaxel

Selamectin

Vinblastine

Vincristine

Vinorelbine

A common over the counter antidiarrheal (loperamide) is also a known substrate. 

ALWAYS discuss this matter with your veterinarian, in case your dog is not tested yet mention this so that your vet can assist you in the process. 

Paw Luna🐾