MDR1 - Multidrug Resistance 1

Multidrug resistance 1 or drug intolerance, MDR1 for short, is a congenital disease that occurs in many herding dog breeds. The mutation in the ABCB1 gene causes a malfunction of the P-glycoprotein, which is responsible for the breakdown of certain drugs and toxins in the body. Clinical symptoms are often associated with the distribution of drugs in the central nervous system. Based on reports that even carriers can develop symptoms of intolerance, it can be assumed that the inheritance is autosomal incompletely dominant rather than autosomal recessive. Autosomal incomplete dominant means that dogs that carry only one copy of the mutation are at increased risk of an adverse reaction to certain medications. Although side effects from certain medications are most often observed in dogs with two defective copies of the gene, the dosage of medications should be adjusted even in carriers of the MDR1 defect. If a dog at risk is treated with one or more common medications (see below*), there is a risk of developing neurological symptoms. These range from tremors and increased saliva production to vomiting, blindness, coma and even death. Because certain medications cannot be metabolized, even small doses can be fatal. Dogs affected by MDR1 show no symptoms unless they are exposed to certain medications. It is therefore important to inform the treating veterinarian about a known diagnosis in order to adapt therapy accordingly.

*Drugs known to cause neurological symptoms in MDR1 carriers or affected dogs:

Acepromazine, butorphanol, doxorubicin, emodepside, erythromycin, ivermectin, loperamide, milbemycin, moxidectin, rifampicin, selamectin, vinblastine and vincristine.

In addition to the drugs mentioned here, there are many others that are removed from the central nervous system in humans via the P-glycoprotein mechanism. However, reports of drug-induced neurological dysfunctions caused by medications other than those listed here are rare in dogs. Please be sure to consult your veterinarian before administering medication to a dog that is an MDR1 carrier or affected by this disease. Even untested dogs from susceptible breeds should be treated with caution. In addition to the drugs mentioned here, there are many others that are removed from the central nervous system in humans via the P-glycoprotein mechanism. However, reports of drug-induced neurological dysfunctions caused by medications other than those listed here are rare in dogs. Please be sure to consult your veterinarian before administering medication to a dog that is an MDR1 carrier or affected by this disease. Even untested dogs from susceptible breeds should be treated with caution.

Delivery takes place as a standard letter. (Delivery time approx. 2-5 working days).
Processing time after sample receipt in the laboratory: usually 7-10 working days.
Examination material: oral mucosa swabs or 1-2 ml EDTA blood.