Encapsulation of finasteride with native and modified γ-cyclodextrins. Extensive characterization of the complexes

The aim of this work was to study the complexation process of FIN with native and modified CDs, to develop an aqueous solution for the topical treatment of male androgenic alopecia. The effect of pH and temperature in the complexation process were studied by solubility studies. The complexes FIN-CDs were characterized by 1HNMR and 2-D NMR (ROESY) spectroscopy. Molecular modeling studies and NMR data were used to build three-dimensional models of the complexes. FTIR, DSC and SEM techniques were also applied to strengthen physicochemical characterization, geometry as well as structural aspects evidencing the effective inclusion of FIN into the CDs’ hydrophobic cavity. The most effective CDs in the FIN complexation were γ-CDs, and their modified HP-γ- and methyl-γ-CDs by forming 1:1 complexes. The Kc value obtained for γ-CDs was 9687 ± 51 M−1, whereas the Kc values obtained for HP-γ- and methyl-γ-CDs were lower, indicating that the presence of HP or methyl groups hinder the entry of FIN in the hydrophobic cavity of γ-CDs. In conclusion, FIN aqueous solubility could be increased by complexation with CDs and the aqueous solutions obtained can be used to improve FIN therapeutic possibilities in a pleasant preparation for the patient that guarantees the adherence to the treatment.