Thermodynamic and kinetic investigation of agomelatine polymorph transformation.

Thermodynamic properties of polymorphic forms I and II of Agomelatine were investigated and the bimorphism was determined to be monotropically related. The phase transition kinetics from metastable form I to thermodynamically stable form II was studied and a quantification method was developed based on X-ray powder diffraction technique. Various solid-state kinetic models were examined and the results were fit to the experimental data. The nucleation kinetic models were found to be the best fit to describe the experimental data across the temperature range. The activation energy of the form transformation was calculated in the range of 116-122 kJ mol(-1), irrespective of which kinetic model selected.