Stability and in vitro activity of nystatin and its γ-cyclodextrin complex against Candida albicans

gamma-Cyclodextrin (gamma-CD) was found to form an inclusion complex with nystatin. In the presence of gamma-CD, cells of Candida albicans absorbed less nystatin than in its absence. The gamma-CD/nystatin complex had no or insignificant antimicrobial activity. Upon diffusion into a gamma-CD-free medium the antibiotic was released from the complex and inhibited growth of the test organism. The stability of nystatin and the gamma-CD complex was studied using both a microbiological and a spectrophotometric assay. The stability of nystatin in aqueous preparations was improved by gamma-CD complexation. Degradation of pure nystatin did not follow first-order kinetics. The loss of antimycotic potency was more rapid than the decrease in concentration calculated from the spectrophotometric data for the pure antibiotic as well as its gamma-CD inclusion complex.