Try using ACCENT, the food seasoning. It is much cheaper than the S.E.P. (I am by no means not saying don't try SEP). I just want to tell you what I did.
My Vet suggested it and it worked. I put a 1/4 tsp sprinkled on his food and he stopped. I only had to do it 1 time. He hasn't done it since and it has been over a year. Just another option I wanted to throw out there.
Good luck!