It is found that direct freeze-drying method is not applicable to oxiracetam because of long time and poor product quality. In this paper

MS software is used to calculate the molecular interactions between additive (sorbitol) and different crystal surfaces of oxiracetam. These values are very small and could be neglected. Experiments also show that the crystal form and morphology are independent of sorbitol in freeze-drying process. Analyzed by differential scanning calorimetry and hot-stage microscopy

glassy sate of oxiracetam prescription is identified during original prefreezing process

against sublimation of water molecules. Therefore

we propose a gradual congelation crystallization technology to change the crystal state of sorbitol

congeal every component and separate them in microcrystalline. According to results of larger scale experiments

this new technique greatly shortens the time required and improves the product quality.