The aim of this study was to investigate if amorphous solid dispersions of telmisartan, prepared in presence
of different polymers, exhibit different structural and thermodynamic characteristics and whether
these differences can be correlated to their physical stability (time to crystallisation) and dissolution
behaviour. Amorphous samples were prepared by melt quenching. The resulting amorphous materials
were characterised using X-ray diffraction, Raman spectroscopy and differential scanning calorimetry.
All freshly prepared samples were completely X-ray amorphous (with a halo being the only feature in
the diffractograms). The shape of the halos in the diffractograms varied suggesting structural variations
in the near order of the molecules between the different amorphous solid dispersions (ASDs). Principal
component analysis of the Raman spectra of the various ASD revealed that the samples clustered in
the scores plot, again suggesting structural differences due to the presence of different drug–polymer
interaction. The ranking of the samples with respect to physical stability and interaction parameter
was: ASD of telmisartan:eudragit > ASD of telmisartan:soluplus > ASD of telmisartan:HPMC > ASD of telmisartan:
PVP > amorphous telmisartan. The interaction parameter, calculated by using the Flory Huggins
theory, showed a good correlation with the experimentally determined stability whereas a weak correlation
was found with dissolution behaviour of different ASD. This study showed that correlation of physical
stability and dissolution behaviour with calculated interaction parameter is possible for the same
amorphous systems prepared by using different polymers. This could aid in selecting the most appropriate
polymer for the development of optimised formulations containing amorphous drugs. It can be concluded
that ASD prepared by using different polymers have different structural and thermal properties.
These differences affect the physical stability and dissolution profiles of the amorphous solids. Thus,
choosing the right polymer for preparing ASD is critical for producing materials with desired dissolution
profiles and enhanced stability.
