Drug Sensitivity can be found more commonly in herding breeds and has been found in Australian Shepherds and Collies. It is caused by a mutation of the Multidrug Resistance Gene (MDR1), which produces a protein called P-glycoprotein. This protein works as a pump to remove toxic substances from the body to prevent the harmful effects of the toxins. In dogs that show Drug Sensitivity that gene is not functioning resulting in toxicity. Dogs with this mutated gene can be sensitive to Ivermectin, which is a medicine commonly used in anti-parasitic products such as heart worm preventives, as well as other drugs including chemotherapy drugs. Symptoms that have been seen regarding this sensitivity have ranged from tremors, depression, seizures, incoordination, hypersalivation, comas and even death. There is no known treatment but there is a new genetic test that can be done.