Crystallization Kinetics of Sulfapyridine, Fluoxetine Hydrochloride and Lidocaine Hydrochloride

摘要

The higher the absorbability, thus the greater the bioavailability, of the amorphous form of an Active Pharmaceutical Ingredient (API) is well known. Therefore, crystallization kinetics of the amorphous form of the drugs can be studied and the subsequent activation energy for both its glass transition and crystallization are significantly important. The thermal properties of both the crystalline and amorphous forms of sulfapyridine, fluoxetine hydrochloride, and lidocaine hydrochloride were investigated by Differential Scanning Calorimetry (DSC) which focused on the crystallization process. Several mathematical models were used to evaluate the data obtained from the experiments. In addition, multiple heat/cool cycles were also applied in this examination to better understand the nature of the API. According to the data, it seems that the drug with high activation energy for crystallization tends to have low glass transition activation energy. The amorphous form of lidocaine hydrochloride did not crystallize under the DSC experimental conditions. However, the amorphous form of lidocaine hydrochloride had the lowest value for its activation energy for the glass transition, followed by fluoxetine hydrochloride and sulfapyridine, respectively. The results demonstrate that sulfapyridine is more likely to be in a crystalline form, compared with fluoxetine hydrochloride and lidocaine hydrochloride which has the greatest tendency to be in its amorphous form among the three APIs.