Preparation of Pharmaceutical Granules:

The meaning and characteristics of granules

Granules refer to granular preparations made from extracts of medicinal herbs and suitable excipients or fine powders of medicinal herbs, with a certain particle size. Its characteristics: ① It maintains the fast absorption and rapid action of the decoction, while overcoming the disadvantages of inconvenient decoction, large dosage, and susceptibility to mold and spoilage when the decoction is in use. ② The granule preparation process is suitable for industrial production and the product quality is stable. ③ Due to its small dosage, it is convenient to take, carry, store, and transport.

Classification of granules

According to their solubility and dissolution state, granules can be divided into: ① soluble granules, which can be divided into water-soluble granules and alcohol soluble granules. ② Suspension granules are often made by adding fine powder of drugs, and when taken orally, they form a uniform suspension. ③ Effervescent granules, due to the addition of an appropriate amount of effervescent disintegrant (such as citric acid or tartaric acid and an appropriate amount of sodium bicarbonate), produce a large amount of carbon dioxide gas when mixed with water, which promotes rapid disintegration and dissolution of the granules.

In addition, there are sugar free granules, which refer to granules without sucrose powder, with smaller doses, and can meet the needs of patients who are not suitable for consuming sugar components in clinical practice.

　Preparation process of granules

1. Processing of raw materials

(1) The extraction and refinement of raw materials vary depending on the active ingredients of traditional Chinese medicine, and different types of granules have different requirements for solubility. Different solvents and methods can be used for extraction and refinement.

(2) The most commonly used excipients currently are sugar powder and dextrin. In addition, β - cyclodextrin and effervescent disintegrants are selected according to application needs.

① Sugar powder is an excellent excipient for soluble granules, and has taste correction and adhesive properties. Sugar powder is prone to moisture absorption and clumping, so it should be sealed and stored carefully.

② Hydrolyzed products of dextrin starch. Soluble dextrin should be selected for granules. Before use, it should be dried at low temperature and sieved.

③ β - cyclodextrin (β - CD) can form inclusion complexes of aromatic volatile components, which can be mixed with particles made from other drugs to pulverize liquid drugs and increase the solubility of oily drugs and the stability of granules.

④ The effervescent disintegrant is a necessary excipient for effervescent granules, composed of organic acids and sodium bicarbonate or sodium carbonate.

2. Particle making

At present, commonly used methods include wet granulation and dry granulation. The dry granulation method will be introduced in the relevant chapters of tablets, with a focus on the wet granulation method.

(1) Wet granulation refers to the process of mixing fine powder or thick paste of drugs with excipients in a suitable container, adding a wetting agent to make a soft material that can be squeezed into a ball by hand and dispersed when pressed, and then passing it through a 14-22 mesh sieve (plate) by extrusion to produce uniform particles. For small-scale preparation, manual granulation sieves can be used, while for large-scale production, swing granulators or rotary granulators are commonly used.

(2) Fluidized spray granulation makes the powder preheat, dry and in boiling state, then makes the powder wet and coagulate into porous particles, and continues to dry until the moisture content in the particles is appropriate.

(3) Spray drying granulation: First, the properly treated extract of medicinal materials or the mixed slurry of drugs and excipients are made into the extract powder by spray drying, and then the excipients are added to the granulator for granulation.