I don't think it's working...
My grouchy cat is about 11 years old. He is grouchy towards the kitten we got for our son last year. If they ignore each other then everything is fine; but the poor kitten wants to play with my grouchy cat so badly, but he just wants to be left alone. So grouchy will hiss at the kitten and run away from playing with him. I've given grouchy to my cat in his wet food for a couple of weeks now and it doesn't seem to have helped. He is still grouchy, and still doesn't want to play with the kitten.