An overview of host-guest chemistry and its application to nonsteroidal anti-inflammatory drugs

The concept of host-guest chemistry has opened the way to the construction of supramolecular (inclusion) complexes with physicochemical properties superior to those of the guest molecule. Several types of host molecules have been synthesised, including crown ethers, cryptands, spherands, carcerands and cyclodextrins. All are able to act as 'artificial receptors' and at least partially enclose guest molecules such as cations and drugs. Cyclodextrins are chemically stable, water soluble oligosaccharide hosts derived enzymatically from starch. Because their interiors are relatively lipophilic and their exteriors hydrophilic, cyclodextrins can complex hydrophobic guests to form inclusion complexes in aqueous solution. Of the 3 types of cyclodextrins (alpha, beta and gamma), beta-cyclodextrin is the best studied. Among the potential advantages of using host-guest complexes in oral drug delivery are enhanced rate and extent of drug (guest) dissolution, and thus improved bioavailability, of poorly soluble drugs. The piroxicam-beta-cyclodextrin inclusion complex typifies this: the complex increases the rate of dissolution and absorption of the original piroxicam molecule. Host-guest complexes, for example piroxicam-beta-cyclodextrin, provide a means to overcome inherent physicochemical difficulties with numerous chemical and medicinal agents. The future looks likely to bring many more opportunities for host-guest chemistry to play a part in our everyday lives.