Cyclodextrins as smart excipients in polymeric drug delivery systems

A few years ago, it has been realized that cyclodextrins (CDs) can be used as aid-excipients in polymeric drug delivery systems (DDS) with the aim to increase drug loading and modify release properties. This effect has been mainly ascribed to their complexation ability toward poorly soluble drugs which improves dissolution properties inside a DDS. From a look to the literature produced so far, it is immediately clear that this concept has severely limited their application in drug delivery technologies, in some cases prompting toward an “evidence-based” rather than rationalized use. For example, it has been neglected, or at least poorly investigated, that several other physico-chemical properties of both the drug and the polymer can be altered in the presence of CDs. Thus, the achievement of a speeding up or slowing down effect on drug release rate upon CD addition has been fortuitous rather than designed “ab initio”. This approach, in our opinion, did not contribute to allow a systemic use of CDs in the engineering of DDS and likely hindered their great potential in the field. In this context, the aim of this chapter is to clarify the effect of CD introduction in different DDS on the basis of their possible interactions with both drug and polymer, thus providing a strong rationale to CD selection and proper use.