Granulation Process In Tablet Manufacture

Granulation is a process where primary powder particles are blended and adhered to form larger, multiparticle entities called granules. Most of the drug substances do not carry the desired properties that would give a satisfactory flow from the hopper to the die cavity of tablet presses. Thus, they are run through pretreatment alone or with suitable excipients to produce free-flowing granules that are easily available for tabletting.

Granules

Granulation is used to improve processability of solids, control dissolution profiles of a drug and eliminate poor content uniformity in final dosage forms. It’s often the first processing step when multiple formulation components are combined.

Read Also: Types of pharmaceutical excipient

Tablets are generally manufactured by three processes, namely, wet granulation, dry granulation or direct compression. These processing methods involve several steps or unit processes like weighing, milling, mixing, granulation, drying, compaction, coating and finally packaging.

Weighing, milling and mixing are common to all the three manufacturing processes and the subsequent unit steps differ in all. All of these manufacturing processes have their advantages and disadvantages. And manufacturers use them as per convenience and need.

Consideration When Choosing Granulation Process

• Chemical and physical endurance of the Active Pharmaceutical Ingredient (API) during the production method

• Compression characteristics of the API

• Availability of the significant processing apparatus

• Particle size of the formulation component

• Cost of the processes involved

Attributes Of Formulation For Tableting

For an active ingredient to be transformed into tablets of satisfactory quality, the formulation must have three essential attributes.

Read Also: Advantage and disadvantage of granulation

First, the formulation must flow into the die space of the tablet press sufficiently rapidly and in a reproducible manner.

Second, the particles in the formulation must cohere when subject to a compressing force, and that coherence should remain after the compressive has been removed.

Third, after the compression event is complete, it must be possible for the tablet to be removed from the press without damage to either the tablet or the press.

Very few active ingredients possess all three of these essentials and some possess none of them. Hence some preliminary treatment is almost invariably necessary.

Direct Compression Process

Without any pre-treatment of the powder blend when it is compressed directly from a powder mixture of API and suitable excipients, then the method is called direct compression. This is a dry process where the powdered tablet formulation is directly compressed into the tablets, without any specific physical nature modification of the former.

Dry Granulation Process

When the granulated ingredients are sensitive to moisture or heat, this procedure is implemented. Granules are produced without the aid of any liquid solution as the name suggests. This technique is used for the preparation of aspirin and other aspirin combinations for tablets.

Read Also: Difference between dry granulation and direct compression

Wet Granulation Process

It is the most commonly used method. Using water as the main granulation fluid, heat is applied to dry the formed granules. This procedure has sufficient mechanical properties and the quality of the tablet is affected by the choice and concentration of binder and the type and volume of granulation fluid. This method is not as efficient as others.

Reasons For Granulation

Pharmaceutical granulation is mostly used for tablet dosage forms, other applications include: capsules, sprinkle products for paediatric patients and production of engineered particles for modified release.

There are several reasons for converting powders or blends of powders into granules and they include:

1. To increase the uniformity of drug distribution in the product

2. To densify the material

3. To produce “dust free” formulations and reduce cross-contamination and hazard associated with the generation of toxic dust that may arise during manufacturing processes

4. Optimise dissolution profiles of tablets

5. To enhance powder flow and powder handling

6. To improve the compression characteristics of drug substances

7. To improve the appearance of a final product

8. To prevent segregation of powder components during tableting or storage

Read Also: Pharmaceutical manufacturing of tablet

Ideal Characteristics Of Granules

For a successful manufacture of tablets, the granules must possess the following characteristics:

 1. All formulation ingredients should be uniformly distributed in the granules

2. A good granulation should be as near spherical in shape as possible to ensure reproducible flow which in turn ensures constant tablet weight throughout the batch

3. Granules of different sizes or density must not separate in the hopper as a result of machine vibration

4. Granules should possess good disintegrating properties and lubrication to reduce die-wall friction

5. The granules should have sufficient fines to fill empty spaces between coarse granules for better compression characteristics

6. A tablet granulation should have sufficient physical strength to form strong tablets when compacted