**7.4 Cyclodextrins**

Cyclodextrins are cyclo oligosaccharides consisting of several glucopyranose units (see Section 6.1). These act as host molecules that form inclusion complexes. Parent cyclodextrins can be modified to extend physicochemical properties and inclusion capacity. Cyclodextrins were shown to help rectal drug delivery with respect to stabilization, release, bioavailability, and alleviation of local irritation. Enhanced rectal absorption of lipophilic drugs by cyclodextrins is due to improved release from the vehicle and dissolution rate in the rectal fluid. However, the enhanced absorption of protein or peptide therapeutics is due to the action of cyclodextrins on the rectal epithelial cells [174].
