Use of thermodynamics in understanding drug release from xanthan gum matrices: The influence of clay-drug complexes

The aim of this study was to outline a novel way of understanding the controlled drug release from drug-clay-polymer matrices using isothermal calorimetry (ITC) as a complementary technique to dissolution studies. ITC results showed that the binding phenomenon between the model drug propranolol hydrochloride (PPN) and magnesium aluminium silicate (MAS) in the presence of xanthan gum (XG was spontaneous and enthalpically driven (negative enthalpy (ΔH) and small entropy (-T∆S)). This may be due to the competition for PPN due to the anionic nature of XG. Dissolution results showed that when using the MAS-PPN complexes, 10 % w/w XG polymer level was enough to significantly reduce the burst release. When used together, ITC and dissolution studies may help a formulator understand and identify interactions which occur during dissolution studies and may be beneficial to the controlled drug delivery system.