Immodium is chemically very similar to Demerol, BUT Immodium does not cross the blood brain barrier, so you ain't gonna get high off of it. Immodium does a heck of a job at slowing down your "bathroom" issues because, to the best of my knowledge, your guts are lined with some kinda opiate receptors too and Immodium, being chemically very similar to an opiate, fills those receptors and calms things down.
As far as I know, Immodium will not cause any kind of prec. wd. either because it doesn't cross the blood brain barrier.
I took Immodium during my Suboxone wd, it helped me to stop crapping every 30 seconds. However, I didn't take Immodium for too long, maybe a week or two, I didn't want to develop any kind of dependence on it.
Be kind to yourself. Our character defects do NOT define who we are!