I truly don't think of him as bi-polar, either. It was just the easiest way to describe his behaviour. I have not had the opportunity to observe him just before an attack; just during and after. As far as I can tell, though, none of the attacks have been provoked by the attackees.
He has never been aggressive towards us, is very sweet with all the other cats (grooms and cuddles), and is actually a big cuddle-bug most of the time. He IS extremely competitive when we play with the feather wands.
Hopefully, the medicine will help.