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Dry Mixing: Intra-granular ingredients with or without the API is intimately mixed in the bowl ofLSMG, HSMG or FBPD
Wet granulation involves the massing of a mix of dry primary powder particles using agranulating fluid. The fluid contains a solvent which must be volatile so that it can be removedby drying, and be non-toxic. The granulation liquid may be used alone or, more usually, as asolvent containing a dissolved adhesive (binding agent) which is used to ensure particleadhesion once the granule is dry. Further mixing of the wet mass is continued to achieve granulation end-point
In the traditional wet granulation method the wet mass is forced through a sieve to produce wetgranules which are then dried. A subsequent screening stage breaks agglomerates of granulesand removes the fine material, which can then be recycled.
Typical liquids include water, ethanol and isopropanol, either alone or in combination. Theprimary advantages of water are that: it is non-flammable, which means that expensive safetyprecautions not be taken. Water is commonly used for economic reasons. The disadvantages ofwater as a solvent are that:
=>> It may adversely affect drug stability, causing drug hydrolysis.
=>> It needs a longer drying time than do organic solvents, that
=>> Increases the length of the process and again may affect stability because of the extendedexposure to heat.
Organic solvents are used when water-sensitive drugs are processed, as an alternative to drygranulation, or when a rapid drying time is required. Fluidized-bed granules are similar to those prepared by the wet granulation, but possess greater porosity and the granule surface iscovered by a film of binding agent.
