I use it on both my dogs. Since we live in a heavily wooded area the Vet recommended it. It works well, so far! The ticks are really bad this year and so far (knock on wood) they have been tick and flea free!
Also I notice that on our walks there aren't any flying "buggies" after them. They all seem to be swarming around my head.

It does say on the package DO NOT USE ON CATS.. It says, "Due to their unique physiology and inability to metabolize certain conmpunds, this product must not be used on cats. If applied to a cat, or ingested by a cat which actively grooms a recently treated dog, this product may have serious harmful effects. If this occurs contact your veterinarian immediately."

I would consult your vet for something that will be safe for both your dog and your cat.