Pellets are spherical or nearly spherical preparations with a diameter ranging from 0.5 to 2mm. It has good fluidity, is easy to fill capsules, and has small differences in filling volume. With the further development of modern pellet technology, the use of pellets in long-acting and controlled release formulations is becoming increasingly common due to their stable, reliable, and uniform drug release characteristics. The early preparation process of microspheres was manual pill making. For example, the preparation process of traditional Chinese medicine pill making mainly includes three stages: molding, shaping, and covering. During preparation, an appropriate amount of cold water (or a wetting agent specified in the prescription) is added to the medicine tablet, brushed evenly with a brush, sprinkled with an appropriate amount of medicine powder, shaken and rotated to make the medicine powder evenly adhere to the tablet and be wetted. Then, the moistened medicine powder is gently brushed off the tablet with a brush to form small particles, which are repeatedly rolled in the tablet to form dense small particles (mother core). Water is added to wet the tablet, and the medicine powder is sprinkled to make it evenly adhere to the mother core.

Micro pill classification

The types of microspheres mainly include: immediate release microspheres, sustained-release or delayed release microspheres. The sustained-release or extended release microspheres include skeleton type, enteric coated type, and insoluble coated type microspheres.

Characteristics of microspheres

(1) Beautiful appearance and good fluidity. (2) High drug content. (3) Easy to produce sustained-release and controlled release formulations. (4) Stable drug release. (5) The bioavailability is relatively high.

Production process

Roll and repeat until the appropriate size of pellets are produced. This operation is cumbersome and difficult to control the main drug content, disintegration, etc. in the finished product, which can easily cause microbial contamination and make it difficult to effectively control the process conditions. With the widespread use of microspheres, their preparation technology has also been greatly promoted and developed. Various pill preparation methods continue to emerge, and the production process has evolved from early manual production to semi mechanized preparation. In 2012, it entered the stage of fully automated preparation.

The pill making technology is constantly improving and perfecting, and micro pill preparations will play an increasingly important role in the modern pharmaceutical industry. Due to the good morphological characteristics, good flowability, and clear drug release features of micro pills, powders and particles in the preparation of hard capsule preparations, especially slow-release and controlled release capsules, will gradually be replaced by micro pills.

In all the production processes of microspheres, there is a binder solution (usually water, ethanol/water mixture, or polymer material solution), which has considerable humidity and viscosity before screening, increasing the difficulty of screening. During the screening process, the instantaneous motion of the microspheres is a combination of radial displacement and circular motion with this displacement as the axis, resulting in a spiral motion. With the emergence of specialized screening screens for microspheres, the problem of manual screening has been solved. Not only does it improve work efficiency, but it also meets the acceptance criteria.

Screening purpose

Removing the pills and granulating them to form adhesions like conjoined twins, with varying sizes of pills and large particles and fine powder inside the granular material, ensuring that the particles are uniform and complete, and the capsules are filled clean and quickly.