<unk>  is the secretion back into the intestines of substances previously taken up from it. It occurs when there is a negative relative concentration of substance in the intestines, making it passively diffuse from the mesenteric<unk>  into the intestinal lumen and is trapped. Examples of toxins that exhibit<unk>  include theophylline, phenobarbital, and phenytoin. Administration of activated charcoal inhibits the<unk>  of such substances, and is therefore useful in overdose or intoxication.
Enteroenteric circulation
Enterohepatic circulation
Intestinal permeability
Intravasation
Fresh gas flow
Initial acquisition of microbiota
Organ gifting
Vascular permeability