Size Reduction is one of the most important steps carried out for pharmaceutical preparations.In this article we will discuss what is the size reduction and pharmaceutical application of size reduction.
What is Size Reduction
The process which is used to reduce the particle size of a substance to a finer state to smaller pieces to coarse particles or to powders is known as size reduction.
For easy understanding, the process of reducing the particle of any substance size is known as size reduction.
Other Names Of Size Reduction
The synonyms of size reduction are
- Comminution
- Grinding
- Milling
When we reduce the particle size of solid materials by using mechanical aids it is known as Milling.
The majority of the materials used in pharmaceutical industries require size reduction and different types of equipment are used for size reduction.
Following are some commonly used equipment for size reduction
- Ball Mill
- Hammer Mill
- Edge Runner Mill
- End Runner Mill
- Disintegrator
- Bohr Stone Mill
- Hand Mill
- Colloid Mill
- Fluid Energy Mill
Pharmaceutical Application Of Size Reduction
- Size reduction is very helpful for those materials which are required for solution formulation. Size reduction increases the surface of materials & due to increased surface area rapid solution formation is achieved.
- The size reduction process is also very helpful for those cases where an extraction process is required. Due to reduced particle size the process of extraction is facilitated due to increased surface area.
- The size reduction also increases the effectiveness of some active pharmaceutical ingredients.
- Size reduction is very helpful where we need to mix different types of solid materials. When particles are fine it becomes very easy to get a uniform powder blend.
Example
Suppose we have metformin and lactose & our goal is to mix these two materials in double cone mixer.We are familiar that metformin is usually available in form of large lumps so if will try to mix,will not get the uniform blend.For uniform mixing we reduce the particle size of Metformin & then mix with lactose to get a uniform blend.
- Size reduction is very important to ensure uniform mixing of crystalline substances.
- For tablet manufacturing, size reduction or milling process is used at various stages.
Examples
At the pre-sieving stage we reduce the particle size to get a uniform blend for the kneading process and after drying the size reduction is done to get uniform-sized granules.
- The size of oil globules in an emulsion affects the stability of the emulsion so by reducing the particle size of oil globules the emulsion stability is improved.
- Particle size is very important for suspension formulation where very small particles tend to form a hard cake and large size particles form a loss cake.
- For all semisolid preparations particle size reduction plays an important role and all formulations must be free from griteness.
- By size reduction, the dissolution profile is improved because due to size reduction surface area is increased.
Disadvantages Of Size Reduction
- The size reduction by the grinding process results in the production of heat which may result in the loss of volatile and aromatic constituents from sensitive materials.
- Due to size reduction, the surface area is increased which also increases the chances of moisture absorption and oxidation reduction.
Factors Affecting Size Reduction
Different factors of the product whose size is required to be reduced has a great impact on the process of size reduction.
The following are the most common factors
- Physical Properties
- Melting Point
- Size Of Starting Material
Physical Properties
The physical properties of materials including hardness of materials and moisture content have influence over the size reduction.
If the moisture content is high it will be difficult to reduce the particle size.
Therefore It is required to dry the products to facilitate the process of size reduction.
If the product hardness is high it will be difficult to reduce the particle size.
Melting Point
The products having low melting point result in sticking due to the heat generating during the process of grinding.
Size Of Starting Material
If the size of starting materials is very large it will be difficult to reduce the particle size in a single step. So the size of these materials is reduced in stages.
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