101: Drug Sensitivity | Dog Gene Mutation

by Nancy Boland

Research has shown that certain dog breeds are sensitive to certain medication, drugs and wormers. This includes antibiotics, pain relief medication and chemotherapy drugs to name but a few. Herding breeds namely Collies, Australian Shepherds and other related breeds when given certain drugs can be  so adversely affected it can be life threatening to them which means it is really important to find out whether your pet is sensitive before they are given them.

Gene Mutation

The reason some dog breeds are sensitive to certain medication is due to a gene mutation which allows certain drugs and medication to build up in their brains. The results is a neurological reaction which causes a dog to demonstrate systems which includes tremors, blindness and disorientation.

What This Means for owners

The fact that pets can now be tested for MDRI, offers dog owners a lot of peace of mind. Knowing it is safe for a dog to be given a specific drug without the risk of them having a extremely severe reaction is a great leap forward in veterinary medicine.

What You Need to Know

For the moment the most affected breeds are herding dogs and related certain mixes but with the number of breeds that are now being tested, it is thought this list may well grow in the future. In the meantime, vets are now able to choose the type of medication when treating a dog knowing they will not cause them any adverse neurological effects.

Below is a list of breeds which are known to have sensitivity to certain medication, wormers and drugs:

Gene Mutation | Drug Sensitivity

  • Australian Shepherds – both standard and miniature
  • Long-haired Whippets – due to their Shetland Sheepdog ancestry
  • English Shepherds
  • Shetland Sheepdogs

Mixed breeds too can be affected so it’s important to know if your pooch has any herding ancestry – the problem being that a few dogs that don’t resemble a herding dog have been identified as having the MDR1 mutation. If you are unsure it is essential to have your pet tested so that vets would know which drugs would be safe to use should your dog need to be given any type of medication.


If you own horses and dogs, you have to be very careful that you dog does not eat any of their droppings after a horse has been wormed because by doing so and if the dog has the gene mutation, they could be permanently blinded.

What You Need to Do

If you are about to get a dog from a breeder, it is essential you ask them if their breeding stock has been given the “all clear”. In an ideal world, both the female and the male would need to be clear of the mutation so their puppies are not passed the gene mutation down. The problem is that within certain breeds the mutation is extremely widespread and as such this makes it very hard not to use any dogs with the mutation in a breeding program.

Testing Puppies & Dogs is Essential

It is really important to have puppies and dogs tested for the mutation whether you are aware of the parent status or not. Ideally, a breeder would have already done this – but if they have not, then you should arrange for a test as soon as you can.

Tests Can be Done by Post

You can have the tests done by post or you may prefer for a vet to do this for you. There are test kits available from online laboratories that deal with veterinary analysis. The test is relatively easy to do because it involves taking a sample of your pet’s DNA by swabbing the inside of their lips and then sending it off for analysis.

Gene Mutation

The results would come back showing your dog has two normal copies of the gene, a normal copy as well as a mutant copy or two mutant copies. Should your pet have two mutant copies of the gene this confirms they are sensitive to certain drugs and medication. If they have one mutant copy, they may be sensitive but in either case, it is essential that you tell your vet so they are aware of the situation.

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