Cyclodextrins, Their Value in Pharmaceutical Technology

Abstract

Cyclodextrins are cyclic oligosaccharides consisting of a variable number of glucose units (usually 6 to 81. The ring formed by cyclodextrins is externally very hydrophilic and relatively apolar internally. In liquid or solid medium, these molecules are capable of forming inclusion compounds with many other molecules. The inclusion compounds thus formed display interesting properties in comparison with the starting molecule.

In fact, inclusion may increase the stability of the guest molecules. Greater stability may be shown towards heat, resulting in lower volatility or higher thermal resistance. Greater stability may also be oxidation resistance. It may also concern the products in solution, whose hydrolysis may, in certain cases, be inhibited to varying degrees. For relatively insoluble active ingredients, inclusion may improve the solubility or dissolution rate. Depending on the stability constant of the inclusion compound formed, a better passage of the active ingredient through membranes may be observed. In vivo, this may be reflected by an increase in bioavailability, with a simultaneous increase in therapeutic effectiveness.