SEARCH Articles Figures Tables Absorption epithelial barriers Absorption epithelial biochemical barrier Barriers to Pulmonary Absorption of Peptides and Proteins Colonic epithelium drug absorption barrier Gastrointestinal lipophilic drug absorption barriers Intestinal absorption barriers Lipophilic drug absorption barriers Lipophilic drug absorption enterocyte barriers Non-metabolic Barriers to Oral Absorption Peptides absorption barriers Proteins absorption barriers The Intestinal Mucosa as a Physical and Biochemical Barrier to Drug Absorption Transdermal absorption skin barrier