Jeanette's Medical Adventures Part III - "But I poop from there!"

[Fathom Zero]

Nutrients and stuff gets lost on their way down to your intestine, which is really just a tube with lots of surface area for absorbing the good stuff. More medicine is absorbed into the bloodstream that way. It wouldn't really work with food because it has to be digested. The intestine can't pull any water out of it. That's also why suppositories are sometimes gel-like and waxy, as you said.