Do not do this. Flea medicine for dogs can and will kill cats. Only get flea treatment for your specific animal, and only from your vet. My fiance has been a vet tech at an emergency clinic for over 7 years, I've heard so many horror stories.Frontline worked for me. I just buy the really big dog version and just measure out the dosage for the animals that need to be treated. Works great and a bit more economical if you have multiple animals.