Capsules are capsule shells that protect drugs. The main raw materials are gelatin, plant cellulose, and their derivatives. They can be divided into hard capsules, soft capsules, and enteric-coated capsules. Different capsules use different raw materials.

Hard capsules: hard capsules are mainly composed of gelatin, plasticizer, and water, and pigments, preservatives, sunscreens, and other ingredients can also be added as needed. According to different raw materials, hard capsules can be divided into animal gelatin capsules and plant capsules. Animal gelatin capsules are made by partially hydrolyzing the collagen contained in animal skin and bones. The main components of plant capsules include film-forming materials, such as hydroxypropyl Methylcellulose, starch, gelling agents (such as pullulan, algin, etc.), and additives (such as potassium citrate, potassium chloride, etc.).

Soft capsules: Soft capsules are mainly composed of capsule walls and contents. The capsule wall is mainly composed of gelatin, plasticizer, and water. The plasticizer can adjust the plasticity and elasticity of the capsule wall. The commonly used plasticizers are glycerin, Sorbitol, and a mixture of the two, the proportion of plasticizer in the soft capsule is greater than that in the hard capsule, and other ingredients, such as pigments, preservatives, sunscreens, and fragrances, can also be added to the capsule wall as needed.

Enteric-coated capsules: Enteric-coated capsules are made by adding special medicinal polymer materials, or cellulose acetate phthalate, hydroxypropyl methylcellulose phthalate, polyvinyl acetate phthalate, etc. to the capsule shell. The enteric coating material makes it insoluble in gastric juice and only disintegrates and dissolves in intestinal juice.