Enteric-coated hollow capsules must meet the alkaline liquid in the intestine to dissolve, and gastric acid is acidic, so the capsule is insoluble in the stomach. If the enteric-coated capsule dissolves in the stomach, it may cause damage to the stomach. At present, the commonly used capsules in clinical practice are gelatin capsules composed of gelatin.

Pharmaceutical gelatin is a high-quality adhesive made of animal skin, bones and tendons, which has undergone complex physical and chemical treatments. It has physical characteristics such as high viscosity, high freezing and easy freezing. The digestive organs of the body are mainly the stomach and intestines. The stomach is mainly acidic and the intestines are alkaline. So, according to this section, there are usually two capsules, one that dissolves in the stomach and the other that dissolves in the intestines. Because some drugs are highly irritating and harmful to the stomach, they do not cause damage to the gut. Therefore, for this part of the drug, it is necessary to make such intestinal capsules.