Use of Stepscan DSC for Freeze-Drying Optimization

The production of many new drugs requires that the active material first be dissolved in water and then freeze-dried or lyophilized in order to generate a compound which is easily ingested and which also has a pleasing or pharmaceutically elegant appearance. The lyophilization process involves cooling an aqueous formulation to subambient temperatures and then pulling a vacuum to drive off the free water. Due to energy consumption considerations, this can be expensive and it is desirable to know the maximum acceptable temperature to which the solution can be cooled before a vacuum is applied. It is also essential to ensure that the temperature is sufficiently low enough to avoid the ‘collapse’ of the freeze-dried cake, which renders an unsatisfactory or useless product.