Preparation and solid-state characterization of inclusion complexes formed between miconazole and methyl-beta-cyclodextrin

The aim of this study is to confirm the formation of inclusion complexes between miconazole (MCZ) and two derivatives of beta-cyclodextrin, methyl-beta-cyclodextrin (MbetaCD) and 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD) in aqueous solution by phase solubility studies. Inclusion complexes with MbetaCD in the solid state were then prepared by different methods, i.e., kneading, coevaporation (COE), spray-drying (SD), and lyophilization (LPh). The physicochemical properties of these complexes were subsequently studied by means of differential scanning calorimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction techniques. Phase solubility diagrams with MbetaCD and HPbetaCD were classified as A(P) type, indicating the formation of 1:1 and 1:2 stoichiometric inclusion complexes. The apparent stability constants (K(S)) calculated from the phase solubility diagram were 145.69 M(-1) (K(1:1)) and 11.11 M(-1) (K(1:2)) for MbetaCD and 126.94 M(-1) (K(1:1)) and 2.20 M(-1) (K(1:2)) for HPbetaCD. The method of preparation of the inclusion complexes in the solid state was shown to greatly affect the properties of the formed complex. Hence, the LPh, SD, and COE methods produce true inclusion complexes between MCZ and MbetaCD. In contrast, crystalline drug was still clearly detectable in the kneaded (KN) product.