The ABCB1 gene, also known as MDR1, contains the instructions for producing P-glycoprotein, a transport pump that prevents certain drugs from accumulating in the brain. Some dogs carry a variant that prevents this protein from functioning properly and may experience severe adverse effects from drugs that are safe for other dogs: neurological symptoms with certain antiparasitic drugs at high doses or some antidiarrhoeal medications, increased sedation with certain sedatives, and greater toxicity from some chemotherapy drugs.
This variant is particularly common in herding breeds, such as Collies, Australian Shepherds and Shetland Sheepdogs, and their crosses, but it can also occur in other breeds.
- In dogs, we analyse this variant in the traits section of the Starter and Advanced tests.
- In cats, a different, rare variant of the same gene has been described that also increases sensitivity to certain drugs. We analyse it in the health section of the Advanced test.
If your dog carries this variant in one or two copies (sensitivity is greater with two copies), or if your cat carries the feline variant, inform your vet before any treatment. They will determine which medications and doses are appropriate. Never change prescribed medication or dosage on your own. For dogs, we analyse this variant from the Starter test onwards; for cats, it is included in the Advanced DNA test for cats.