The elements that create a good batch of tablets are not found in the tableting process: instead, they're found in the granulation process. Granulation compresses tiny particles together before the material is spheronized and the end result is a product that has improved flow characteristics, improved uniformity and conformity and reduced fine dust, which in turn helps to improve tablet yield, boosts productivity which means that more tablets can be made in a shorter period of time and reduces the number of tablet defects that occur.

Pharmaceutical granulation is the process of bonding various particles together. This can either occur through compression or by using a binding agent. As a basic rule, something as fine as powdered sugar, for example, would be difficult to form into a tablet as the powder has poor flow characteristics. Normal granulated sugar, on the other hand, would be much easier to compress into a tablet as the particles are slightly larger. Granulation forms very fine powders into slightly larger powders, which then allows them to be compressed, spheronized and tableted.

Granulation simply combines one or more particles of powder into slightly larger granules, which allows for them to then be tableted quickly and easily. Another benefit of granulation is that it's an easy way to combine active and non-active ingredients, ensuring the even spread of ingredients and that each tablet contains the right quantity of each ingredient. Blending is sometimes not enough to combine the ingredients, particularly if there is an active component. The active component can often cause a number of problems, including segregation of ingredients, differences in the size of the particles, differences in moisture content, differences in density and differences in flow characteristics. One of the ways to get around this incompatibility problem is by using granulation.

In this application, the active ingredient is first granulated, before being combined with the rest of the granulated ingredients. This granulation process helps to stabilise that active ingredient. Another solution is to combine the powders evenly before granulating them together. Each granule would contain a small quantity of each and every ingredient which means that the end result is a stable tablet with just the right amount of the active ingredient. This not only improves productivity and uniformity, but it also improves the shelf life of the product.

There are a number of techniques used in the granulation process – compression, dry granulation and wet granulation. These techniques are outlined in more detail below.

• Compression: Direct compression is a technique used when the ingredients can simply be mixed together, deposited onto a tablet press and then compressed. In this technique, none of the ingredients have to be altered. It's often worth just putting the ingredients onto the press to see whether they form a tablet. If not, additional processes can be used in future.
• Wet granulation: When powders are too fine and will not compress together, granulation should be used. Wet granulation ranges from the complex to the simple, but the basic process involves adding a liquid solution to the dry powders. Often, this is all that is needed to form granules. The solution can range from water to different types of glue.
• Dry granulation: Dry granulation does not use a liquid solution and this is often used when the particles are sensitive to moisture or to heat. The powders will instead be compacted, but instead of being compacted into tablets, they are compacted into small granules. This is often a long process as it tends to take some time for the particles to compact together.

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