The granulation is a method where powder particles are made to bind to one another, resulting in large, multi-particle bodies, called granules. If the process is done with the addition of granulating liquid, it is known as wet granulation and if the process is carried without liquid, it is known as dry granulation.
The dry granulation process is used to make granules without liquid, as the granulating material can be sensitive to heat and moisture. In this process, the powder mixture is compacted by exerting a force on the powder, which in general causes a considerable size increase. There are two ways to achieve compact when using dry granulation: slugging and roller compaction.
The steps involved in dry granulation are- weighing formulation ingredients, mixing of formulation ingredients, compression of mixed powders into slugs, milling, and sieving of slugs, mixing with disintegrants and lubricants, and compression of granules into tablets, etc.
Advantages of dry granulation:
- The major advantage of dry granulation is that the formulation does not have moisture content, because granular liquid or solvent is not used in the process. It is suitable for pharmaceuticals (drugs or excipients) that are sensitive to moisture.
- The dry granulation process requires less equipment, less space, more economic than wet granulation.
- The drying step is not involved in this type of method, hence it is suitable for heat-sensitive materials.
- Dry granulation does not require any special excipients; it uses conventional grades of material.
- Tablet manufacturing by dry granulation improves the disintegration time.
- The rate of dissolution of tablets produced by dry granulation does not decrease with aging.
Disadvantages of dry granulation:
- The main disadvantage of dry granulation is that since it does not form granules, it may not have better flow properties.
- The dry granulation method leads to low flowability, compressibility, and cohesiveness of the powder, causing the powder to not easily flowing and compressed.
- The process produces a lot of dust which can lead to cross-contamination.
- It requires a special heavy-duty apparatus for granulation.
- Dry granulation tablets are softer than wet granulation tablets which make them difficult to tablet coating or film coating.
- It extensively damages the sieving screening and other tools which are used in the process.
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