A capsule is a preparation in which a drug is encapsulated in capsule body and cap, usually divided into a hard capsule and a soft capsule. Drugs encapsulated in capsule shells are generally irritating drugs for the esophagus and gastric mucosa, or some drugs that are not good in taste and are easily volatile. These drugs are contained in the capsule shell, which can mask their own bad odor, protect the drug from damage, and avoid irritating our esophagus and stomach.