Interactions of terbinafine with β-cyclodextrin polymers: sorption and release studies

Abstract

β-cyclodextrin insoluble polymers (βCDP), a type of hydrogels with a high swelling capacity, can be obtained by crosslinking β-cyclodextrin (βCD) with epichlorohydrin. Terbinafine (TB) is an oral and topical antifungal drug that can be housed into the cavity of β-cyclodextrin, so it seems probable that the drug could interact with the insoluble βCDP. Different organic molecules can be sorbed on the polymer network and also included within the βCD cavities, so these hydrogels have potential applications in the pharmaceutical field as drug carriers. In this work, the sorption of TB on βCDP and the optimal conditions to load the polymer with the drug were studied. Sorption kinetics and Freundlich isotherms of TB on βCDP at 25°C were obtained and the influence of several parameters on the sorption process of TB was investigated. It was found that a high initial concentration of drug, high TB:β-CD molar ratios and low ionic strengths were the most favourable conditions. No significant influence of temperature was observed. Moreover, the sorption kinetic profile obtained for terbinafine was compared to that of naftifine, another antifungal agent of similar structure. Terbinafine presented higher affinity for the polymer, according to the higher stability constant of the drug-βCD inclusion complex. In relation to the release studies from the loaded polymer, 0.1 M HCl was the most favourable medium to allow the release of the drug. The maximum amount of drug released in 24 h was up to 50% of TB loaded. The predominant mechanism of drug release was Fickian diffusion.