Certain Collies and other breeds of herding dogs as well as hounds are sensitive to the avermectin class of drugs. In fact, ivermectin-sensitive Collies are bred for this trait because before the Food and Drug Administration’s Center for Veterinary Medicine approves new avermectin products, it requests that they be tested in these dogs.

If the product is found toxic when administered to ivermectin-sensitive Collies, the safety margin is considered inadequate for the drug to be used even in the general dog population.

A genetic mutation is responsible for ivermectin sensitivity. It affects dogs that are homozygous-recessive for a deletion in multidrug-resistance gene 1, which encodes for P-glycoprotein.

The CVM’s approach toward this MDR-1 defect is an example of how the agency is refining the use of drugs on the level of individual patients.

Individualized medicine, or pharmacogenomics, is an area where CVM Director Stephen F. Sundlof predicts much progress. This field of research focuses on variations in the molecules that interact with medicines moving through the body. Dr. Sundlof and CVM Deputy Director Bernadette M. Dunham spoke with AVMA News recently about the agency’s future directions and recent challenges.

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