Thermal investigation of crystallization of polyethylene glycols in solid dispersions containing oxazepam

A critical issue in the processing of solid dispersions is to elucidate the microstructure of the resulting product. Morphological features such as crystallinity degree of both carrier and drug, and particle size of the latter, have a deep effect on the properties of the drug dissolution. In the present paper, Hot Stage Microscopy (HSM) has been employed to investigate the crystallization of polyethylene glycols (PEG) of different molecular weights used in the processing of a benzodiazepine (oxazepam). The results have shown that the crystalline morphology and the radial growth rate were dependent on the polymer molecular weight, crystallization temperature, and also on the molecular state of the drug incorporated into the polymer, forming a solid dispersion and strongly influencing the drug dissolution rate.