We have friends who in addition to the lactulose sprinkle BeneFiber on the
cat food twice a day. It helps a lot. The cat hasn't had a problem in
months. I understand this wasn't the main part of your question, but if it
could be of some help...

Thats interesting as I presume that its a fibre suplement. He's
actually been perscribed a low fibre food, and I thought (in humans
anyway) that high fibre was good in this sort of thing