Capsules have a very long history. As early as 1500 BC, the first capsule was born in Egypt; in 1730, pharmacists in Vienna began to make capsules with starch; in 1834, the capsule manufacturing technology was patented in Paris; in 1846, the two-section hard capsule manufacturing technology Obtained a patent in France; in 1872, the first capsule manufacturing and filling machine was born in France; in 1874, the industrial manufacturing of hard capsules began in Detroit, USA, and various models were introduced at the same time.
Capsules are usually divided into hard capsules and soft capsules. Hard capsules, also known as hollow capsules, are composed of two parts of a cap body; soft capsules are made of film-forming materials and contents at the same time. According to the raw materials, hollow capsules generally include: gelatin hollow capsules and plant hollow capsules. At present, the large-scale production of plant hollow capsules in China is mainly hypromellose hollow capsules, so the current domestic hollow capsules are mainly gelatin hollow capsules and hypromellose (HPMC) hollow capsules. Empty capsules for comparison.

1. The raw materials used are different.

The main component of gelatin hollow capsules is high-quality medicinal gelatin. Gelatin is derived from collagen in animal skin, tendons and bones, and is a protein partially hydrolyzed from collagen in animal connective tissue or epidermal tissue. The main component of HPMC hollow capsules is 2-hypromellose, which is usually cellulose obtained by hydrolysis of plants, and is made by etherification. Due to religious beliefs (Judaism, Islam, etc.), dietary habits (vegetarianism), the need to advocate green nature, and the prevention of animal-derived diseases (mad cow disease), the use of plant capsules in the world is increasing year by year.

2. The chemical structure stability of the shell is different.

There are lysine residues in gelatin, the adjacent lysine residues are oxidized and deaminated to generate acetaldehyde groups, and the aldol-amine condensation reaction generates pyridine rings and cross-linking. Therefore, gelatin is used as the capsule material, and the capsules are placed during the placement process. There is a delay in disintegration. HPMC is part of methyl and part of polyhydroxypropyl ether of cellulose, with stable chemical properties and no cross-linking, so there will be no delay in disintegration. In addition, some groups containing aldehydes, reducing sugar-based compounds and vitamin C in the content will react with amino or carboxyl groups in gelatin, and affect the disintegration of the capsule shell and affect the stability of the drug, so this type of drug is not suitable for use. Suitable for use with gelatin hollow capsules. Gelatin contains groups such as carboxyl and amino groups, so the capsule shell will have an electrostatic effect. During the drug filling process, the capsule shell is prone to adhesion and easy adsorption of the contents. The HPMC capsule shell has little or no electrostatic effect.

3. The water content is different.

Under the condition of 20~25℃ and RH 40%~60%, the water content of gelatin hollow capsule shell is about 13%~15%, and under this condition, the water content of hypromellose hollow capsule shell is about 4% to 6%. The gelatin hollow capsule shell becomes brittle when the water content is less than 10%, while the HPMC hollow capsule shell does not become brittle even when the water content reaches 1%. Excessive water content has a great influence on the stability of moisture-sensitive drugs. For the contents with strong hygroscopicity, if gelatin hollow capsules are used, the water will migrate from the shell to the contents, and the water of the shell will become hard and brittle, resulting in delayed disintegration, but there is no such phenomenon when using HPMC hollow capsules.

4. The coating properties are different.

The surface of HPMC hollow capsules is rougher than that of gelatin hollow capsules, and its affinity with most enteric coating materials is significantly higher than that of gelatin. Reliability is significantly improved. It is not suitable to use organic solvents such as ethanol, which are easy to deform gelatin, and HPMC is chemically inert, so it can be used for aqueous coating and organic solvent coating such as ethanol. The good coating performance of HPMC makes it have obvious advantages in the preparation of slow-release and controlled-release coated capsules and targeted formulations.

5. The additives are different.

The main component of gelatin hollow capsules is protein, so it is easy to breed bacteria and microorganisms. Preservatives and bacteriostatic agents need to be added during the production process, so that there may be residues on the capsules, and ethylene oxide must be used before the finished product is packaged. Sterilization method to ensure the microbial control index of the capsule. The HPMC hollow capsules do not need to add any preservatives during the production process, and do not require ethylene oxide sterilization.

6. The storage conditions are different.

Tests have shown that HPMC capsules are almost invariable and brittle under low humidity conditions, do not generate static electricity, and remain stable under high humidity conditions. There is no problem in storage in all climatic zones, and even more in transportation. Gelatin capsules are prone to sticking under high humidity conditions, hardening or brittle under low humidity conditions, and are highly dependent on the temperature, humidity, humidity and packaging materials of the storage environment, and even have higher requirements for transportation, especially In summer, a refrigerated truck is required to ensure the quality of the capsules.
To sum up, HPMC hollow capsules have obvious advantages over gelatin hollow capsules in many aspects. Although it is impossible to replace the dominance of gelatin hollow capsules in a short period of time, their applications in medicine and health food are still relatively low. There will be a rapid growth trend.
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