Luckily I do not suffer with constipation, in spite of being on oxycodone. I have always had a slow bowel, but I am one of the luckier ones on the board, as I don't have to resort to laxatives or enemas, just the occasional dose of stool softener.
Oddly enough, fresh fruit seems to stimulate me as easily as the stool softener, and it's much tastier too. I am careful, though, about what I eat for fruit - I love all fresh fruit, but I know that some of it will make me worse instead of better.
Hugs for your son.
Nancy in NB