Pelletization is an agglomeration process that converts fine powders or granules of bulk drugs and excipients into small, free flowing, spherical or semi spherical units, referred to as pellets. Pellets range in size, typically, between 0.3 – 1.5 mm, though other sizes could be prepared. Pellets can be prepared by many methods, the compaction and drug-layering techniques being the most widely used today. Regardless of which manufacturing process is used, pellets have to meet the following requirements.

• They should be near spherical and have a smooth surface; both considered optimum characteristics for subsequent film coating.
• The particle size range should be as narrow as possible. The optimum size of pellets for pharmaceutical use is considered to be between 600 and 1200 μm.
• The pellets should contain as much as possible of the active ingredient to keep the size of the final dosage form within reasonable limits.
• For such purposes, coated pellets are administered in the form of hard gelatin capsules or disintegrating tablets that quickly liberate their contents of pellets in the stomach.
• Pellets are for pharmaceutical purposes and are produced primarily for the purpose of oral controlled-release dosage forms having gastro resistant or sustained-release properties or the capability of site-specific drug delivery.
• As drug-delivery systems become more sophisticated, the role of pellets in the design and development of dosage forms is increasing. Formulation of drugs in multiple-unit dosage forms, such as coated pellets filled in capsules or compressed into tablets, offers flexibility as to target release properties.

The safety and efficacy of the formulation is higher than that of other dosage forms. Pellets provide high degree of flexibility during the design and development of oral dosage forms. They can be divided into desired dose strengths without formulation or process changes, and can also be blended to deliver incompatible bioactive agents simultaneously or particles with different release profiles at the same site or at different sites within the gastrointestinal tract.

In addition, pellets have numerous therapeutic advantages over traditional single units, such as tablets and powder- filled capsules. Taken orally, pellets generally disperse freely in the gastrointestinal tract, and consequently maximize the drug absorption, minimize local irritation of the mucosa by certain irritant drugs because of the small quantity of drug available in a single pellet, and reduce inter and intrapatient variability 2 . As the advantages of pellets over single units became clear, the pharmaceutical industry as a whole started to devote resources to conduct research in pellet technology and, whenever possible, acquire advanced equipment suitable for the manufacture of pellets.

Pellets may be manufactured by using different methods according to the application and the choice of producer. The methods used for Pelletization are essentially the same as the granulation methods. The most widely used processes are extrusion and spheronization and solution or suspension layering, and powder layering. Other processes with limited application in the development of pharmaceutical pelletized products include globulation, balling, and compression. ADVANTAGES OF PELLETS: They can be divided in to desired dosage strength without process or formulation changes. When pellets containing the active ingredient are in the form of suspension, capsules, or disintegrating tablets, they offer significant therapeutic advantages over single unit dosage forms. They can also be blended to deliver incompatible bioactive agents.

They can also be used to provide different release profile at the same or different sites in the gastrointestinal tract. Pellets offer high degree of flexibility in the design and development of oral dosage form like suspension, sachet, tablet and capsule

Flexibility of pellets in development of dosage form.

• Pellets disperse freely in gastro intestinal tract (GIT), maximize drug absorption, and minimize local irritation of the mucosa by certain irritant drugs.
• Improved flow characteristics: Spheres have excellent flow properties
• Coating: Coating of granules is often applied for stabilizing active ingredients in the granule or to control the release of these active ingredients. Typical applications in the pharmaceutical industry are the controlled release medicines. The easiest shape to coat is the sphere due to the absence of edges. It is also the most economical one to coat as no extra coating material is required to fill irregularities in the surface of the granules
• Density increase: Both the true and the bulk density of granules are increased by spheronising. This can improve the process and the packaging.
• Marketing: For consumer products, spheronising is sometimes only applied for improved product appearance and marketing reasons.
• Hardness and friability: Hardness and friability depend on the internal cohesive forces and surface characteristics. Spheronization increases the hardness and reduces the friability of granules. This will reduce the amount of fines generated during handling or transportation.