Differential scanning calorimetry and thermally stimulated depolarization currents study on the molecular dynamics in amorphous fenofibrate

Abstract

The slow molecular mobility of the active pharmaceutical drug fenofibrate is studied by differential scanning calorimetry (DSC) and thermally stimulated depolarization currents (TSDC). The general kinetic features of the secondary relaxations and of the main relaxation, in particular their distribution of relaxation times, were determined by TSDC. Different experimental procedures were used to determine the fragility index by DSC and the obtained results were discussed. The TSDC fragility is in very good agreement with the value obtained by dielectric relaxation spectroscopy (DRS), and all the DSC, TSDC and DRS values indicate that fenofibrate is a very fragile liquid. Given that this means a strong aging sensitivity, we profited from this property to evaluate the influence of physical aging on the fragility values determined by TSDC. From the results of experiments designed to achieve this goal we can conclude that this influence can be considered as negligible.