Tableting Process: Granulation in the Pharmaceutical Industry

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What is Granulation?

In the pharmaceutical industry, granulation refers to the process by which small powder particles are made to adhere together to form larger, multi-particle entities known as granules.
It involves gathering powder particles by establishing bonds between them, typically through compression or the use of binding agents.

Granulation is widely used in the production of:

Tablets
Pellets (or spheroids)

The process combines one or more powders to form granules that make subsequent tableting or spheronization easier and more efficient, while staying within required quality limits.

Why is Granulation Important?

Fine powders—especially those in the sub-10 micron range—pose major handling challenges. They tend to be cohesive, have poor flowability, and can generate hazardous dust.
Granulation addresses these problems and brings several benefits, including:

Elimination of dust hazards
Enhanced flowability
Improved control over:
- Wettability
- Bulk density
- Product appearance
- Compressibility
- Abrasiveness
- Drying properties
- Absorptive capacity
- Solubility

Granulation also helps prevent powder segregation and ensures better content uniformity in the final product.

Tableting Methods and Unit Operations

Process Type	Common Steps
Direct Compression	Milling and mixing → Tablet compression
Dry Granulation	Milling and mixing → Roll compaction or slugging → Milling/screening → Lubricant mixing → Tablet compression
Wet Granulation	Milling and mixing → Binder solution prep → Wet massing → Wet screening → Drying → Dry screening → Final blending → Tablet compression

Pros and Cons of Each Tableting Method

✅ Advantages

Wet Granulation	Dry Granulation	Direct Compression
Improves flow through increased particle size and sphericity	Enhances flow and density uniformity	Simplest process with fewer steps
Ensures uniform API and color distribution	Improves cohesion during compression	Reduces processing time significantly
Effective for bulk powders; minimizes environmental contamination	No need for liquid binders	Suitable for moisture- and heat-sensitive APIs
Lower compression pressure required	—	Fewer formulation variables reduce dissolution changes over time

❌ Disadvantages

Wet Granulation	Dry Granulation	Direct Compression
Time-consuming wetting and drying stages	Risk of over-compaction affecting dissolution	High risk of content variation in low-dose products
More equipment and processing steps are required	Potential for particle segregation	Susceptible to unmixing due to static or density differences
Greater chance of cross-contamination	—	Poor flowability with certain excipients can lead to issues

Conclusion

Choosing the right granulation and tableting method depends on factors such as API properties, desired tablet characteristics, and manufacturing conditions.
Understanding these methods helps pharmaceutical professionals optimize efficiency and ensure high-quality tablet production.