The main purpose of the capsule is to prevent the burn of the medicine on the esophagus. It is not conventionally recognized to protect the capsules from rupture in the stomach, while reducing to stimulate intestinal absorption. Because ordinary gelatin-based capsules (which account for the absolute majority) will still rupture under gastric acid conditions. Capsules are generally considered to be classified as follows:

    1) Hard capsules, soft capsules

    2) Two-section capsule, one-piece capsule

    3) Solid content capsules, liquid content capsules, semi-solid content capsules

    4) Conventional capsules, microcapsules

    5) Controlled-release capsules, ordinary capsules (sustained-release, targeted, gastric-coated, enteric-coated, gastric floating, and other capsules all belong to the controlled-release category)

    Enteric-coated capsules exist, but different from conventional capsule shells, the capsule shells are made of special materials, which do not dissolve in gastric acid conditions, and do not cause too much deformation, and only dissolve in the intestinal pH environment.

    Sustained-release capsules do not rely on the sustained-release effect produced by the capsule shell, but rely on the particles in the capsule. It is assumed that the rupture of the capsule shell is almost instantaneous, and all the drugs in the capsule are released to the corresponding parts in an instant, and it cannot play the role of slowly releasing the drugs in it. Some people say that most of the capsules can not be broken, but only a small opening, so that the drug in it can slowly run out (there are really some sustained-release tablets in this way). However, this cannot make the drug run out of it evenly, and the cost will be very high. In fact, the principle of slow-release capsules is similar to making the active ingredient granules into something similar to "tubs", which are slowly melted and absorbed in the intestinal tract.