I just used this product on Wed evening. One for my dog, and one for my cat. My dog is prone to seizures, but did okay with it. My cat on the other hand, he had a horrible reaction to it. He had seizures, shaking, twitching, falling, the whole thing was just horrific. Brought him to the vet and put him on fluids, gave him a bath and some other meds. Took him home last night, and he has stayed in the same spot for nearly 14 hours. He is very lethargic. Vet said he may be okay in a couple days, and then again he could have another seizure and not come out of it at all. I wish I knew about this web site and this hartz product !! We usually use Frontline, this is the first and LAST time we ever use ANY store product. Why is this stuff still on the market? Has anyone had a cat that survived and then had complications? Thanks.