Increasing the cyclodextrin complexation of drugs and drug bioavailability through addition of water-soluble polymers

For a variety of reasons, including cost, production capabilities and toxicology, the amounts of cyclodextrin (CD) that can be included in drug formulations is limited and, thus, it is important to develop methods which can be applied to enhance the complexation efficacy. Moreover, bioavailability of drugs in CD containing vehicles can be rather limited resulting in less than optimal drug delivery. Addition of small amounts of a water-soluble polymer to the aqueous complexation media enhances the CD complexation of drugs. Thus, less CD is needed to dissolve a given amount of drug when a polymer is present than when it is not present in the aqueous complexation media. Furthermore, the bioavailability of drugs is enhanced through addition of polymers. In general, the water-soluble polymers improve both pharmaceutical and biological properties of drug-CD complexes. This polymer enhancement of drug complexation and bioavailability is independent of the physicochemical properties of the drug. Thermodynamic studies and other physicochemical observations indicate that the polymers participate directly in the drug-CD complexation.