When a solid drug shows polymorphism that can affect efficacy, safety, and quality of the drug, it is necessary to perform qualitative and quantitative controls on crystalline states of drug in solid preparations, semisolid preparations, suspensions, etc. To ensure the controllability of efficacy, safety, and quality, the preponderant crystalline state should be selected as crystalline state of drug in the clinic, which should also be preserved in drug preparations.

When multiple crystalline states exist for a drug, the preponderant crystalline state refers to the form that has good clinic efficacy, nice safety profiles, and high stability, and is suitable for drug development.

The crystalline substance formed by two or more chemical substances is called eutectic, which belongs to the category of crystalline substances.