Cyclodextrins.

Although cyclodextrins (CDs) have been studied for over 100 years and can be found in at least 35 pharmaceutical products, they are still regarded as novel pharmaceutical excipients. CDs are oligosaccharides that possess biological properties that are similar to their linear counterparts, but some of their physicochemical properties differ. CDs are able to form water-soluble inclusion complexes with many poorly soluble lipophilic drugs. Thus, CDs are used to enhance the aqueous solubility of drugs and to improve drug bioavailability after, for example, oral administration. Through CD complexation, poorly soluble drugs can be formulated as aqueous parenteral solutions, nasal sprays and eye drop solutions. These oligosaccharides are being recognized as non-toxic and pharmacologically inactive excipients for both drug and food products. Recently, it has been observed that CDs and CD complexes in particular self-assemble to form nanoparticles and that, under certain conditions, these nanoparticles can self-assemble to form microparticles. These properties have changed the way we perform CD research and have given rise to new CD formulation opportunities. Here, the pharmaceutical applications of CDs are reviewed with an emphasis on their solubilizing properties, their tendency to self-assemble to form aggregates, CD ternary complexes, and their metabolism and pharmacokinetics.