Glassy pharmaceuticals were prepared by cooling the melts and their state was confirmed by measuring the glass transition temperature (Tg) and the anomalous endothermic peak (heat capacity maximum) in the differential scanning calorimetry (DSC) curves. Glass formation was newly discovered for 24 pharmaceuticals including acetaminophen, chloramphenicol, flufenamic acid and proxyphylline. The value of the ratio Tg and melting temperature (Tm) of these pharmaceuticals lay between 0.69 and 0.85. The rate and quantity of relaxation of glass was determined by the area under the anomalous endothermic peak of the DSC curves of glasses prepared at various cooling rates, that of glassy griseofulvin was found to have the largest among the pharmaceuticals examined. The apparent activation energy of glass transition of chenodeoxycholic acid, griseofulvin and tolnaftate prepared at the cooling rate of -1.25K/min was calculated to be 273.6, 270.3 and 127.6kL/mol, respectively. The influence of heating rate on Tg and the area under the anomalous endothermic peak of the DSC curve of glassy aspirin both immediately and after standing for 60 min at 232K following preparation of the glass was examined. Both factors decreased as heating rate decreased. The apparent activation energy of glass transition of both samples of aspirin was calculated to be 105.6kJ/mol.
No takes yet. Share an insight, caveat, or question.
Fukuoka et al. (1991) studied this question.