Ivermec works but can be very harmful if used wrong. You really need to know what you are doing with it. Was at a AKC hunt test and this subject came up. Well, as it turned out we had three vets that were handlers at this test. The three of them couldn't agree on the dose to give a 70 lb dog. Like I said, it does work fine but really isn't for the average guy. We used to us it, but went to interceptor a few years ago because mom, me, or my brother could give it with no problems when dad was gone.