I'm not sure about filtering it, that could remove some problematic substances but you probably won't get everything out of it. You'd have to look at all the ingredients of the oramorph and then figure out their size and whether or not they would be removed with a 0.2 micron filter.
I personally wouldn't risk it... maybe if you do a search on BL there might be a way to extract the morphine, I can't remember if I have ever seen a method for that before.