Inclusion complexes of β-cyclodextrin and polymorphs of mebendazole: Physicochemical characterization

Mebendazole (MBZ), designated as a WHO essential drug, can exist in diverse solid forms and presents low absorption at the gastrointestinal level. Considering the potential of cyclodextrins to enhance the solubility and permeability of drugs, inclusion complexes of polymorphs A and C of MBZ with beta-cyclodextrin were obtained. The characterization of the complexes in solid state was performed by using a combination of experimental techniques including Fourier transform infrared spectroscopy, powder X-ray diffractometry and solid state nuclear magnetic resonance. Moreover, the effect of the binary complexes on their physical stability was evaluated. In addition, for a complete characterization of polymorphs A and C, one dimensional spectra and correlation nuclear magnetic resonance experiments were employed. Our physical studies showed that the inclusion complexes were new crystalline forms that induced shifts and broadening in the infrared and nuclear spectra. A molecular modelling analysis performed on the inclusion modes, demonstrated that the most favourable structure for the complex was the head down orientation. Moreover, the intermolecular interactions calculated for the complex with the atoms in molecules theory are in good agreement with the spectroscopic results. The inclusion complexes exhibited an increment of solubility in simulated physiological media. Furthermore, it was demonstrated that the complex formation did not affect the physical stability of the polymorphs.