Do not give this prevention  to collies that have the sensitivity syndrome!  I use is Ivermectin on Normal/Normal result on the MDR1 test.  It is a 1% injectible cattle wormer with the trade name of Ivomec ™ . You can purchase it (without a prescription) for $40 - $50 from a feed store or through a catalog from a Vaccine Wholesale Supplier. The bottle comes in a 50cc size. I give it  by the mouth. I use 1/10th of 1cc for each 10 pounds of body weight. Use a small syringe. Open the dog's mouth. I then tip its head up and squirt the contents of the syringe in the roof of its mouth. Close the mouth and hold it closed until the dog swallows. Do not accidentally squirt the liquid into the dog's windpipe and/or lungs. I repeat only some of my collies can have ivermectin. the rest get the once a month pill from the vet that is safe for collies.

Ivermectin