Manufacture Of Pharmaceutical Tablet By Dry Granulation Process

Tablet manufacture involves granulation. There are three types of granulation. In this post, we will focus on dry granulation.

Dry granulation of tablet

Definition Of Dry Granulation

Dry granulation is a process whereby granules are formed without the aid of any liquid solution. The process is used if the ingredients to be granulated are sensitive to moisture or heat. Compaction is used to densify the powder and form granules.

Read Also: General properties of pharmaceutical tablet

Dry granulation, also referred to as precompression or double compression, is a size enlargement process designed to improve the flow and compression characteristics of powders that would otherwise be unsuitable for compression. The process involves compaction of powder particles into large pieces or compacts which are subsequently broken down into granules to produce granules that can be further processed into dosage forms.

Reason For Dry Granulation

Dry granulation is used in the manufacture of tablets in place of direct compression if the formulation ingredients are too fluffy or too susceptible to flowability problems. It is also an option when the ingredients are too susceptible to degradation from heat and/or moisture for wet granulation for densification. The process is cheaper and simpler compared to the others with less processing time and/or equipment requirements to reduce costs.

Read Also: Pharmaceutical tablet evaluation

The manufacture of tablets by dry granulation method eliminates a number of unit operations but still include milling or micronization of drugs, weighing, mixing, slugging, dry screening, lubrication, and compression of granules into tablets.

For successful manufacture of tablets using dry granulation, either the active ingredient or the diluent must have sufficient inherent binding or cohesive properties.

Dry Granulation Process

The pharmaceutical blend is fed into the feed hopper of the compactor where an auger is feeding the material into the nip of the rolls. Between the rolls the powder is pressed to so called flakes. In a subsequent Flake Crusher the flakes will be broken to granules. The typical granule size varies to 10 to 18 mesh. Typically these processes require machines which are easy to clean and guarantee a high quality of the produced granules. The quality of the granules needs to be validated.

Read Also: Powders use in granulation

Type Of Dry Granulation

The process is carried out using a slugging tool or a roller compactor/ tablet press machine.

Slugging

Slugging is a pre-compression process for the formation of extra large tablets (slugs), usually of variable weight, due to poor flow of the drug powder. The y tablet press or, more usually, a large heavy-duty rotary press for this process. The resulting slugs are subsequently broken down into granules using a hammer mill or other conventional milling equipment. The milled slugs are passed through a screen of desired mesh for sizing, lubricant added and are recompressed to obtain the final tablets.

Read Also: Excipient use in pharmaceutical drug formulation

Roller Compactor/Tablet Press

Roller compaction is a method of powder compaction of dry powders into a solid mass known as the ribbon. This process is achieved by feeding powder through a set of directly opposed, counter-rotating rollers. The process avoids the use of liquids and high temperatures. The ribbon is broken down into a specific granule size via a milling system, such as an oscillating mill.

Read Also: Manufacture of pharmaceutical tablet

The two main categories of roller compaction are essentially based on the gap between the rollers. The first being fixed gap rollers and the second described as ‘floating’, meaning it is possible to change the distance between the rollers depending on the powder properties.