My vet had me try a product called Laxatone. It works really well, if you can get it down the cat. I have had to put it on my Jazz's paws, and then hope he doesn't flick it off. They hate stuff on their paws and will usually lick it off right away. The pounce treats work well too. The Science diet with the hair ball stuff was too much for Jazz, he got very loose stools from it (a nice mess) To use it up I mixed it sparingly with his regular Science diet till it was gone..