In drug research and development, crystal research runs through all stages from the screening of lead compounds to the final drug marketing. From the discovery of two crystal forms of benzamide in the 18th century, to the search for "superior drug crystal forms" of innovative drugs, and the need for "consistency evaluation" of generic drugs, crystal research has become one of the important contents in the process of drug development. For enterprises, drug crystal quantitative research in addition to drug quality control is of great significance, in terms of intellectual property rights, drug crystal patents are also the focus of attention.
The crystal state of the drug does not refer to the difference in appearance, but refers to a set of parameters obtained by a certain detection method to characterize the internal structural state of the drug. The crystalline forms of drugs include various states formed by different arrangements of drug molecules, and also include eutectic states formed when co-existing with other molecules. At present, there are many methods to study drug polymorphism, such as X-ray diffraction, DSC, LM and so on. X-ray diffraction is non-destructive and has more advantages than other methods in the study of the structure of solid substances, especially in the study of crystalline substances. It can carry out drug crystal stability under high temperature, low temperature or high humidity environment, and carry out effective analysis of the composition and structure of drug samples.
X-ray diffraction is divided into single crystal X-ray diffraction and powder X-ray diffraction, which can effectively characterize the drug crystal form from different directions and depths. Among them, single crystal X-ray diffraction is used to determine the crystal configuration and molecular arrangement as well as the configuration of drug molecules, while powder diffraction can give qualitative or quantitative analysis results by testing the powder diffraction pattern, which is mainly used in the purity of chemical drugs, crystal type, stability of raw materials, as well as the content of raw materials and crystal type changes in pharmaceutical preparations.
