Tabletting Process Granulation

Tabletting Process Granulation in Pharmaceutical

Tabletting Process Granulation


−In the pharmaceutical industry, granulation refers to the act or process in which primary powder particles are made to adhere to form larger, multiparticle entities called granules.

−It is the process of collecting particles together by creating bonds between them.

−Bonds are formed by compression or by using a binding agent.

−Granulation is extensively used in for the manufacturing of tablets, pellets (or spheroids).

−The granulation process combines one or more powders and forms a granule that will allow tableting or spheronization process to be within required limits.

The purpose of a granulation step

It can be a challenge to handle fine powders, with materials in the sub-10 micron range being especially problematic. The strong attraction forces between fine particles lead to high cohesivity and flowability, compromising efficient manufacture and use. Such materials can also present a dust hazard.

These issues are tackled by the granulation of fine powders, eliminating any dust hazard, improving flowability and enabling the close control of:

  • Wettability
  • Bulk density
  • Product appearance
  • Compressibility
  • Abrasiveness
  • Drying properties
  • Absorptive capacity
  • Solubility

Granulation  can also help prevent segregation, thereby ensuring product uniformity.

−Some powders are difficult to compact even if a readily compactable adhesive is included in the mix, but granules of the same powders are often more easily compacted.

Typical unit operations in tableting methods

Direct compression Dry granulation Wet granulation
Milling and mixing of drugs and excipients Milling and mixing of drugs and excipients Milling and mixing of drugs and excipients
Compression of tablet Compression into slugs or roll compaction Preparation of binder solution
Milling and screening of slugs and compacted powder Wet massing by addition of binder solution or granulating solvent
Mixing with lubricant and disintegrant Screening of wet mass
Compression of tablet Drying of the wet granules
Screening of dry granules
Blending with lubricant and disintegrant to produce “running powder”
Compression of tablet

Tabletting Process Granulation in Pharmaceutical

Good points

Wet granulation Dry granulation Direct compression
  1. Improved flow by increasing particle size and sphericity
  2. Uniform distribution of API, colour etc. – improved content uniformity
  3. Good for bulky powders, less dust and environmental contamination
  4. Lower compression pressure, less wear and tear on tooling
  1. Improved flow by increasing particle size
  2. Improved uniformity of powder density
  3. Improved cohesion during compression
  4. Granulation without addition of liquid
üFewer processing steps: blending and compression − reduced processing time

üProcessing without moisture and heat – fewer stability problems

üRapid and most direct method of tablet compression

üChanges in dissolution less likely on ageing since there are less formulation variables


Not so good points

Wet granulation Dry granulation Direct compression
•Large number of processing steps

•More equipment

•Wetting and drying stages are time consuming

•Greater possibility of cross contamination

•Possible over compaction of slugs/compacts – impact on dissolution

•Possible particle segregation

•Possibility of lot to lot variations due to differences in psd, flowability and moisture of excipients

•Higher risk of content uniformity failure in low dose products (geometric granulation indicated)

•Lack of moisture can create static charges that can result in un-blending

•Differences in particle size/density between API and excipient can result in un-blending in hopper

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