- Granulation is the process of particle size enlargement by forming agglomerates (granules) to improve flowability, compressibility, and uniformity of powders before tablet compression.
- It is classified into wet granulation, dry granulation, and direct compression.
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Wet Granulation:
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Definition:
- Involves the use of a liquid binder to form granules by agglomerating the powder particles.
- Suitable for drugs that are not sensitive to moisture or heat.
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Process:
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Weighing and Mixing:
- API and excipients are blended uniformly.
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Binder Addition:
- A liquid binder (e.g., starch paste) is added to form a wet mass.
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Wet Sieving:
- Wet mass is passed through a sieve to form granules.
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Drying:
- Granules are dried using an oven or fluid bed dryer.
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Sieving (Sizing):
- Dried granules are resized to ensure uniformity.
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Lubrication and Blending:
- Lubricants and glidants are added for compression.
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Advantages:
- Improves flow and compressibility.
- Uniform drug distribution for low-dose drugs.
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Disadvantages:
- Time-consuming and costly.
- Not suitable for moisture- or heat-sensitive drugs.
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Dry Granulation:
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Definition:
- Granules are formed without using liquid binders.
- Suitable for moisture- or heat-sensitive drugs.
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Process:
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Weighing and Mixing:
- API and excipients are blended.
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Slugging or Roller Compaction:
- Powders are compacted using high-pressure rollers (roller compactor) or slugging (tablet press) to form large sheets or slugs.
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Milling and Sizing:
- Compact material is broken down into granules of desired size.
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Lubrication and Blending:
- Lubricants are added before final compression.
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Advantages:
- Suitable for moisture- and heat-sensitive drugs.
- Faster and cost-effective (no drying).
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Disadvantages:
- High-pressure equipment needed.
- Poor binding properties and dust generation.
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Direct Compression:
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Definition:
- Tablets are made by directly compressing powdered materials without prior granulation.
- Suitable for drugs with excellent flowability and compressibility.
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Process:
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Weighing and Mixing:
- API and excipients are blended.
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Lubrication:
- Lubricants and glidants are added.
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Compression:
- Direct compression into tablets using a tablet press.
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Advantages:
- Simple, fast, and economical.
- Ideal for heat- and moisture-sensitive drugs.
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Disadvantages:
- Requires excellent flowability and compressibility.
- Not suitable for low-dose drugs due to segregation.
- compressibility requirements.
- Lack of uniformity for low-dose drugs.
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Comparison Table
| Aspect | Wet Granulation | Dry Granulation | Direct Compression |
| Process Complexity | Complex, multiple steps. | Moderate, fewer steps. | Simplest, no granulation. |
| Cost | High (equipment, time). | Moderate (no drying). | Low (minimal processing). |
| Suitability | Not for heat/moisture-sensitive drugs. | Suitable for sensitive drugs. | Ideal for free-flowing powders. |
| Tablet Strength | Strong and uniform. | Moderate strength. | Depends on powder properties. |
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