I was looking through the new Drs. Foster and Smith and saw a new Rx I hadn't seen before. It was a product called Advantage Multi that has a flea medicine (Imidacloprid) as well as Moxidectin (often known as Cydectin, used as a livestock wormer) as a heartworm preventative. It is applied topically to both cats and dogs. Cats: http://www.drugs.com/vet/advantage-multi-imidacloprid-moxidectin-topical-solution-for-cats.html Dogs: http://www.drugs.com/vet/advantage-multi-for-dogs.html The above links have information as well as doseage rates. If you used the injectible cydectin at 10mg per ml, it might be feasible for use with cats and dogs. Cydectin pour on would need big dose sizes at 5mg per ml. It's still an Avermectin so it's not safe for Collies or Collie crosses given orally... It DID say that it was used on avermectin sensitive collies TOPICALLY with no ill effects though. I use ivermectin at .1cc per 10lbs with my dogs, but thought it was interesting that you could give moxidectin to cats safely to prevent heartworms. I'm wondering if you couldn't give it orally if you were giving just the moxidectin. It's administered orally to goats.