Pellets & Pelletization Flashcards
Advantages of spheroids as multi-unit dosage form
Therapeutic:
- Minimise local irritation
- Maximise absorption/bioavailability
- Less susceptible to dose dumping
- Reduce GER
Technological:
- Superiority for coating
- Uniformity in packing
- Spherical in shape
- Good flowability
- Low friability
What are the Pelletization techniques?
1) Direct pelletization
2) Pelletization through extrusion step
3) Pelletization by layering onto starter seeds
4) Pelletization through formation of droplets
What is Fluid Bed Layering
- Pelletization by layering onto starter seeds
- -> Layering: Deposition of successive coats onto the seed particles without agglomerative growth
What is the Balling Process used for?
Use: Produce nonpareils as well as agriculture and industrial pellets, industrial pellet production use
Eg. of Direct Pelletization
1) Pelletization in Rotary Processor
- a “one-pot” pelletization process
- Conducted by spraying the agglomeration media directly onto the powder mass rotating in a spheronizer on a frictional base
- Pellets formed in situ; can be directly coated by changing spray media to coating media with introduction of drying air
What is the method of choice for producing pellets?
Extrusion-spheronization
Advantages of Extrusion-spheronization
- Ease of operation
- Efficient, High throughput with low wastage
- Produces highly spherical aggregates
- Pellets have narrow size distribution
- Pellets have smooth surface
- Pellets have low friability
Steps in Extrusion-spheronization process
1) Dry blending
2) Wet massing
3) Extrusion (Radial/Axial extruder)
- moistened powder mixture is introduced & processed in the extruder to form high-density, cylinder shaped extrudates
- pass extrudates through screen of desired aperture size
4) Spheronization
- extrudates are broken into uniform length & rounded in a spheronizer with a rotating frictional plate to produce spheroids
- rapid process
- shaping process due to plastic deformation
5) Drying
6) Coating
Formulation requirements of extrusion-spheronization
Extrusion:
- Wet mass is cohesive & plastic with inherent fluidity & self-lubricating properties
Spheronization:
- Extrudates have sufficient plasticity
Basic formulation:
- Pelletization aid
- Drug
- Filler
- Moistening liquid
What is the Pelletization aid of choice?
Microcrystalline cellulose (MCC)
- Good binding property
- Good cohesiveness
- Large SA
- High internal porosity
–> Gives unparalleled efficiency for preparing highly spherical granules of narrow size distribution with desired mechanical properties
Functions of MCC?
- Absorbs H2O like a “molecular sponge” during extrusion
- > Give a cohesive yet plastic wet mass
- > Help in binding & extrusion
- Help in binding & lubrication in spheronization
- -> Increases surface plasticity & helps in rounding extrudates into pellets
Examples of Pelletization Aids
- Microcrystalline cellulose, MCC Ideal
- Cross-linked polyvinyl pyrrolidone (very successful)
- Powdered cellulose
- Hydroxyethyl cellulose
- Chitosan
- Carrageenan
- Hydroxypropyl methylcellulose/Hypromellose
Small/larger particles favoured for ensuring pellet sphericity?
Ans: Small
- Will form agglomerates that are more spherical, smoother surface, narrow size distribution
What is the moisture requirement by mixer torque rheometer (MTR)?
- Peak of the graph
- Moistening liquid added to powder mass in the mixer bowl of the MTR
- Rheological profile of moistened powder mass is obtained
What is the strategy for successful pelletization
- Ensuring wet packability*
- Critical for influencing spheroid formation
- Depends on the particle size & size distribution of its components & forces exerted during wet processing
Dry powder —[moistening liquid]—> Wet mass
Wet mass — Extrusion —> Extrudate
Extrudate – Spheronization —> Round spheroids with
narrow size distribution
During spheronization, cohesive forces should be ~ forces to make good extrudates
