Abstract
The great philosopher Hegel proposed a concept of spiral progression of things. In the other word, nothing is lost or destroyed but elevated and preserved as in a spiral. The past will re-emerge with progress. Epithelium covers the body and separates the inner body from the outside environment. Passage of drugs across epithelium is inevitable step for drug absorption. Thus, permeation of drugs across epithelium is a basic strategy for drug absorption. A concept for permeation-enhancement by modulating intercellular seals in epithelium was proposed over 50 years ago. Recently, progress in understanding the biology of the epithelial seals has provided us new insight into drug absorption. In this review, we overview spiral progression of the permeation enhancers.
