How does Vicodin enter the body?

In the stomach, and the small intestine - and to a certain degree, the medication can be released without the pill being completely dissolved. I believe the "shell" for want of a better Word is permeable and that effective plasma levels can be achieved even should the pill appear to pass through the body intact. I know this because I have seen whole pills in my stool, and yet I consistently achieve a therapeutic effect from taking the medication (pain reduction)aas directed, so either we're all being duped, or my assessment is reasonably correct.