Granulation Process ,Reasons for Granulation and Types of Granulation
Granulation :
In Granulation process small particles adhere to each other due to formation of bonds between them resulting in the formation of large multiparticle masses called “Granules”.Granulation is done after initial dry mixing of the necessary powdered ingredients along with the active pharmaceutical ingredient (API) to obtain uniform distribution of each ingradient in the powder mixture.
The size range of Pharmaceutical granules ranges between 0.2 and 4.0 mm, In many cases this will be in the production of capsules and tablets.
Reasons for granulation
1. To produce a homogenous and uniform mixture that doesnot segregate into layers.
2. To enhance the flow properties of the granules.
3. To enhance the compaction characteristics of the drug mixture.
4. Problem of dust during compression can be prevented by granulation processs.
5. Particles of uniform in size can be produced.
6. To increase the density of the powdered mixture as a result it occupies lesser volume per unit weight for better storage
7. Granulation allows to control and achieve bulk density of powder mixture with in desired limits.
Methods of Granulation
Granulation methods can be divided into two types:
1.Dry Granulation
In the dry granulation the powder particles are combined under high pressure. This technique is suitable for drugs that are:
1.Senisitive to moisture.
2.Drugs that undergo degradation when exposed to high temperatures during drying process.
3.Drugs that a re administered in high doses.
Dry granulation of powdered mixture can be accomplished by 2 methods :
a)Slug formation(slugging).
b)Roller compaction Method.
In slugging material to be granulated is subjected to compression for prolonged period prior to final compression this results in the formation of a compact mass called slug .Slugging process expels the air traped in powdered mixture making the mass denser and simultaneously enhancing the flow properties of formed granules.
In Roller compaction method the powdered mixture is compressed between two rollers to produce ribbon shaped compact masses.The roller compaction process is done in specially designed equipment called “Roller compactor”.
To determine its(roller compactor) suitability for a given material a trail run of roller compactor along with powder is conducted before this process.
In both the cases the intermediate products are broken down through a suitable milling technique to produce granular material .This granular material is sieved to separate the required size fraction.
2.Wet Granulation
It is the most widely used conventional and versatile method for preparation of compressed tablets as it imparts all physical properties of granules.
In wet granulation process drug is added to the granulator and grinded. Then blended with suitable adjuvants in a blender followed by addition of granulating fluid . The fluid contains a volatile solvent which can be removed by drying and the solvent should be nontoxic. Typical liquids used include ethanol, isopropanol and water These liquids can be used either alone or in combination.
The granulation liquid may be used alone or, as a solvent mixture containing a binding agent .For economical and ecological reasons Water is commonly used as solvent .
Water as solvent can adversely affect stability of drug , resulting in hydrolysis of products, and it needs a drying for prolonged period when compared to organic solvents. This increases duration of process which may cause instability issues because of the prolonged exposure to heat.
Authored by :
S.M.Imroz , M.Pharm(Pharmaceutics).,
S.M.Imroz , M.Pharm(Pharmaceutics).,
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