Binary systems of nifedipine and various cyclodextrins in the solid state - Thermal, FTIR, XRD studies

Nifedipine complexes with beta-cyclodextrin (beta-CD), gamma-cyclodextrin (gamma-CD), 2-hydroxypropyl-beta-cyclodextrin (2HP-beta-CD), randomly methylated-beta-cyclodextrin (RM-beta-CD) and heptakis(2,6-O-dimethyl)-beta-cyclodextrin (DM-beta-CD) have been prepared by both kneading and heating methods and their behaviour studied by differential scanning calorimetry (DSC), diffuse reflectance mid-infrared spectroscopy (FTIR) and X-ray diffractometry (XRD). DSC revealed the nifedipine melting endotherm with onset at approximately 171degreesC for the kneaded mixtures with beta-CD, gamma-CD and 2HP-beta-CD, thus confirming the presence of nifedipine in the crystalline state, while some decrease in crystallinity was observed in the DM-beta-CD kneaded mixture. With RM-beta-CD, however, broadening and shifting of the nifedipine endotherm and reduction in its intensity suggested that the kneading could have produced an amorphous inclusion complex. These differing extents of interaction of nifedipine with the cyclodextrins were confirmed by FTIR and XRD studies.