IN VITRO EVALUATION OF DIFFUSION AND RHEOLOGICAL PROFILES FOR DEXAMETHASONE INCLUSION COMPLEXES WITH β-CYCLODEXTRIN OR HYDROXYPROPYL β-CYCLODEXTRIN

Dexamethasone (Dmt), is very potent glucocorticoid, and inclusion complexes formed with cyclodextrins (Cd), enhance skin penetration. Five gels were prepared representing combinations of the drug with lyophilized or simple physical mixtures of βcyclodextrin (Bcd), or hydroxypropyl β- cyclodextrin (HBcd), in the 1:1 molar ratio. The paper presents in vitro measured values of these forms by using a vertical diffusion cells system and a rotational rheometer. The experimental conditions represented an adaption of the USP Topical/Transdermal Ad Hoc Advisory Panel stimuli for revision process. The aim of this study was to evaluate the improving of skin penetration by Dmt in different mixtures with two Cd, by using the drug release and rheological profiles. Diffusion coefficients of Dmt inclusion complexes with Cd significantly increased compared with the single use of Dmt. The best released rate of Dmt was obtained for the lyophilized inclusion complex with Bcd. A significant diffusivity increase was noticed for the physical mixtures. Data fitted five kinetic models approximating the diffusion profiles. The Korsmeyer‐Peppas model gave the best correlation between measured and interpolated data. All the rheological investigated gels presented shear-thinning and thixotropic behavior. A nonlinear model fitted the rheological data. The obtained profiles suggest better performances of Dmt inclusion complexes for topical applications.