I agree, with the bypass surgery, you will have trouble absorbing many things and the extended release medication is more than likely, not going to work. If you can't take the fentnyl patch, (I don't know anything about the morphine patch) maybe check into Oxycodone, they do make it in liquid form that may be a good alternative for you. Good luck to you.
That's right, because of the decrease in the intestine length makes it likely that extended-release preparations pass through the gastrointestinal tract before absorption is complete. Good thing you remembered that.
Probably have to have instant- release or didn't they use to make morphine patches?? Here's a link for an article about this.
http://www.ajhp.org/content/63/19/1852.full
These same principles can also apply to delayed-release and enteric-