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Advantages of wet granulation
1. Wet granulation modifies the properties of formulation components to overcome their tableting deficiencies. The formed granules are relatively more spherical than the powder and have better flow properties.
2. The improved compressibility of the powders resulting from the wet granulation process allows the use of less pressure during compression. It reduces machine wear and thus improves machine life.
3. The process uses conventional excipients and is therefore not dependent on the inclusion of special grades of excipients.
4. It ensures better content uniformity especially for soluble low-dose drugs.
5. The process can improve the dissolution rate of poorly soluble drugs by imparting hydrophilic properties to the granule surface.
6. Wet granulation prevents segregation of components of a homogeneous powder mixture during processing, transfer, handling and/or storage, thereby reducing intra- and inter-batch variability.
7. Tablets produced by wet granulation are suitable for post-processing unit operations such as tablet coating.
8. Wet granulation reduces the level of dust present during the manufacturing process thereby reducing the incidence of cross-contamination and risk to workers.
9. Wet granulation reduces air entrapment thereby increasing powder compressibility.
Limitation of Wet Grains
1. Wet granulation often requires several processing steps.
2. Wet granulation costs more due to the time, labor, energy, equipment and space required for the process.
3. The process is not suitable for thermolabile and moisture-sensitive materials.
4. Migration of soluble dyes may occur during the drying process.
5. Incompatibilities between the constituent elements will be increased by the granular solvent which tends to bring them into close contact.
6. Transfer of material from one unit operation to another is likely to result in loss of material during processing.
7. The dissolution rate of tablets formulated with wet granulation may decrease with aging.
Despite all these limitations, tablets are still being manufactured using wet granulation for the following reasons:
a. Availability of comprehensive information on existing product manufacturing by wet granulation. This has made pharmaceutical companies reluctant to adopt new strategies unless there is a compelling reason to do so
b. Years of formulation experience have also shown that wet granulation and tablets ensure good content uniformity.
c. The drying process can be manipulated to produce granules with desired moisture content.
