Thermal behavior and molecular mobility in the glassy state of three anti-hypertensive pharmaceutical ingredients

Abstract

The slow molecular mobility in the amorphous solid state of three active pharmaceutical drugs (valsartan, telmisartan and irbesartan) has been studied using differential scanning calorimetry (DSC) and the dielectric technique of thermally stimulated depolarization currents (TSDC). The thermal behavior of the three substances (melting, glass forming ability, glass stability) and the features of their amorphous solid state (glass transition, activation energy for the structural relaxation) were studied by DSC. The TSDC study of the mobility in the glassy state yielded the main kinetic features of the α- and of the secondary relaxations. According to the obtained results the three studied glass forming drugs behave as strong liquids and telmisartan is the one with the greatest dynamic fragility.