Pelletization is the process of converting fine powders or granules into small, free-flowing, spherical units.
It can be achieved through various techniques:
Common Pelletization Techniques:
Extrusion-Spheronization:
The most widely used method for producing pellets.
Steps:
Mixing and Wet Massing: The drug and excipients are blended, and a binder solution is added to form a wet mass.
Extrusion: The wet mass is passed through an extruder to form cylindrical extrudates.
Spheronization: The extrudates are broken into smaller units and rounded into spherical pellets in a spheronizer.
Drying: The pellets are dried to reduce moisture content.
Layering Techniques:
Used to apply layers of drug or excipients onto an inert core.
Types:
Solution/Suspension Layering: A solution or suspension of the drug is sprayed onto the cores while rotating in a pan or fluidized bed.
Powder Layering: Dry powder is layered onto cores, followed by binder spraying.
Direct Pelletization:
Involves forming pellets directly from powders in high-shear granulators or fluidized bed processors without the extrusion step.
Often requires specialized excipients like MCC.
Cryopelletization:
Used for temperature-sensitive drugs.
The liquid formulation is dropped into liquid nitrogen, forming frozen pellets.
Hot Melt Extrusion:
Suitable for drugs with poor water solubility.
The drug and polymer are melted and extruded to form pellets.