MDR1 Gene Defect in Dogs 

Many canine ailments respond well to medication. However, for dogs with the MDR1 gene defect, these drugs can cause significant harm. This genetic disorder is found in many dog breeds and can have serious consequences. In this article, we’ll inform you about the gene defect and its dangers.

How dangerous is the MDR1 gene defect in dogs?

The MDR1 defect is a genetic disorder that makes affected dogs of certain breeds particularly sensitive to certain medications.

If animals with the defective MDR1 gene consume a too-high dose of these medications, central nervous system disorders can occur. This can even be fatal, as the active substances reach the brain unfiltered. For this reason, the administration of some medications to animals with the gene defect is prohibited.

Symptoms: What are the signs of the MDR1 gene defect in dogs?

Symptoms can occur whenever a dog with the MDR1 defect ingests substances that are dangerous for it. Active substances then cross the blood-brain barrier unhindered.

In healthy animals, this barrier protects the brain from external influences. If its function is disrupted, severe damage occurs in the brain, leading to central nervous system failures.

Symptoms include:

• typical signs of poisoning such as vomiting or drooling
• movement disorders
• trembling and stupefaction

If the dose is too high and the poisoning too severe, dogs can fall into a coma and, in the worst case, die from the effects.

When should I go to the vet?

Do not hesitate to visit your vet if you suspect poisoning in your dog. The first minutes and hours are crucial for counteracting the poisoning and possible consequences of the MDR1 gene defect.

Diagnosis: How is the MDR1 gene defect in dogs detected?

Today, it’s possible for vets to identify the MDR1 gene defect via a simple blood test. The vet takes 0.5 millilitres of non-coagulable EDTA whole blood from your dog and sends it to a specialist laboratory for further analysis.

The lab extracts the genomic DNA (deoxyribonucleic acid) from this sample for PCR testing. The polymerase chain reaction helps to determine whether a mutation (referred to as “nt 230 (del4)”) exists in the MDR1 gene, indicating a defect.

How is the MDR1 gene defect inherited?

The gene’s function is limited in this case because the defective MDR1 gene lacks four base pairs compared to an intact gene. The defect can be inherited in two ways:

© Bianca / stock.adobe.com

Therapy: Is treatment of the MDR1 gene defect in dogs possible?

Since it’s a hereditary disease, targeted treatment of the MDR1 gene defect is not possible. However, if your dog suffers from poisoning due to the MDR1 defect, therapy is generally symptom-dependent.

In severe cases, often hospitalisation in an animal clinic is necessary. There, the sick animal is stabilised and receives life-saving measures.

Which medications should dogs with the MDR1 gene defect not take?

To prevent poisoning in a dog with the MDR1 gene defect, it must not take any risky medications. The following groups of drugs that your MDR-1 affected dog should never ingest include primarily:

• Parasiticides: Doramectin, Emodepsid, Ivermectin, Milbemycin Oxime, Moxidectin
• Antidiarrheals for humans: Loperamide

There are also other medications considered concerning for MDR-1 dogs. They contain various active substances found in the following medications:

• Antibiotics: Erythromycin
• Heart medications (cardiac glycosides): Digoxin
• Anti-nausea medications (antiemetics): Ondansetron
• Medications for treating epilepsy (antiepileptics): Acepromazine
• Painkillers (e.g., opioids): Apomorphine, Butorphanol, Loperamide
• Chemotherapeutics (cytostatics): Dactinomycin, Doxorubicin, Paclitaxel, Vincristine, Vinblastine

Important: Never administer medications to your animals without speaking to your vet first.

Beware of medicated environments

Dangerous substances not only enter a dog’s body through medication administration – they also lurk in the environment.

For example, MDR1-affected dogs may eat the faeces of horses that have been dewormed. This too can lead to poisoning.

Causes: What triggers the MDR1 defect in dogs?

To better understand the MDR1 gene defect in dogs, it’s useful to know the function of the MDR1 gene. These three facts should be known:

• The MDR1 gene (Multidrug-Resistance Transporters) has the role of limiting the uptake of harmful foreign substances such as drugs or environmental toxins into the brain or intestines.
• It also aids in quickly excreting the toxins via the liver or kidneys, preventing poisoning of the animals.
• If the MDR1 gene is damaged by a mutation, these defence mechanisms are absent. This is why affected dogs are sensitive to an overdose of medications.

Prognosis: Can the MDR1 gene defect in dogs be cured?

Since the MDR1 defect is genetically induced, a cure is not possible. Therefore, it’s imperative that your affected dog avoids taking any dangerous medications.

If it shows signs of poisoning, visit your vet promptly. This gives your furry friend the best chance to survive the poisoning with the least damage.

Prevention: How can I protect dogs from the MDR1 defect?

To ensure that there’s no risk to your pet when taking medications, it’s advisable to determine its MDR1 status.

A PCR test is not only sensible if you don’t know your dog’s status but also to prevent the spread of the mutation.

You should get a PCR test to detect the MDR1 gene defect if therapy with medications is upcoming or if you plan to breed with predisposed breeds.

Important for adopting a dog: If you opt for a dog from a commonly affected breed, you should definitely ask breeders or previous owners about the dog’s MDR1 status.

This article from zooplus Magazine is purely informative. If your pet is experiencing discomfort, contact your veterinarian for diagnosis and treatment.

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