pelletisation_6

Question 1

definition of pellets

Answer 1

small, round,, ball/tube shaped compressed massed of a substance

Question 2

definition of spheroids

Answer 2

solid geometrical figure similar in a shape of a sphere

Question 3

how does round shape minimise energy

Answer 3

reduce friction during motion

Question 4

therapeutic advantages of spheroids as multi-unit dose form

Answer 4

1. minimise local irritation
2. maximise absorption/ bioavailability
3. less susceptible to dose dumping
4. reduction in gastric emptying rates

Question 5

technological advantage of spheroids as multi-unit dose

Answer 5

1. superiority for coating
2. uniformity in packing
3. spherical in shape
4. good flow ability
5. low friability

Question 6

types of direct pelletisation

Answer 6

1. aqueous-based pelletisation

2. melt-based pelletisation

Question 7

types of pelletisation through extrusion step

Answer 7

1. extrusion spheronisation

2. hot-melt extrusion

Question 8

types of pelletisation by layering onto starter seed

Answer 8

1. powder layering
2. solution layer
3. suspension layering

Question 9

types of pelletisation through formation of droplets

Answer 9

1. spray drying
2. spray congealing
3. cyro-pelletisation

Question 10

what is layering

Answer 10

similar to coating, deposition of successive coats onto seed particles without agglomerative growth, the coating medium is solution or suspension of the core material

Question 11

how is pelletisation in rotary processor works

Answer 11

carried out by spraying the agglomeration media directly onto the powder mass rotating in a spheroniser on a frictional base. Pellets are formed in situ and they can be directly coated by changing the spray media to a coating media with the introduction of drying air into the chamber

Question 12

extrusion spheronisation

Answer 12

• highly spherical aggregates
• pellets of narrow size distribution
• pellets of smooth surface
• pellets of low friability

Question 13

extrusion spheronisation process steps

Answer 13

1. dry blending
2. wet massing
3. extrusion
4. spheronisation
5. drying
6. coating

Question 14

ideal extrudate for spheronising

Answer 14

jagged, feature with regular spaced shark-skinned protuberance

Question 15

formulation requirements for extrusion-spheronisation

Answer 15

1. specific requirement for extrusion (cohesive, plastic wet mass with inherent fluidity and self-lubricating properties)
2. specific requirement or spheronisation (extrudates with sufficient plasticity)
3. basic formulation (pelletisation aid, drug, filler, moistening fluid)

Question 16

choice of pelletisation aid and properties

Answer 16

microcrystalline cellulose (MCC) - pelletisation aid of choice

• good binding property
• good cohesiveness
• large surface area
• high internal porosity
• gives unparallel efficiency for preparing highly spherical granules of narrow size distribution and with the desired mechanical properties

Question 17

molecular sponge model of MCC

Answer 17

• MCC absorbs water like molecular sponge during extrusion (forms cohesive yet plastic wet mass)
• helps in binding and lubrication during spheronisation (increases surface plasticity, and helps in rounding extrudates into pellets)

Question 18

crystalline gel model of MCC

Answer 18

MCC particles are broken down into single crystallites of colloidal size which are able to form a crystalline gel and immobilise the liquid

Question 19

function of MCC

Answer 19

1. absorbs water like molecular sponge
2. extrusion gives a cohesive yet plastic wet mass, helping to bind and lubricate
3. spheronisation increases surface plasticity, helping to round extrudates into pellets

Question 20

example of other pelletisation aids

Answer 20

• powdered cellulose
• hydroxypropyl methylcellulose/ hypromellose
• hydroxyethyl cellulose
• chitosan
• carrageenan
• cross-linked polyvinyl pyrrolidone (v successful)

Question 21

bad examples of pellet formation during spheronisation step

Answer 21

• poorly formed extrudates
• fragments
• build up pellets slowly

Question 22

good examples of pellet formation during spheronisation

Answer 22

• well formed extrudates
• break into short lengths
• round quickly

Question 23

ideal size of components

Answer 23

1/6-1/8 of desired pellet size

note: the smaller the particles, the more favoured it is

Question 24

what mean torque to use for pellet making

Answer 24

@ Tmax, usually at capillary stage

Question 25

what happens when cohesive forces < forces during spheronisation

Answer 25

irregular shaped, wide size distribution, leading to

1. spheronisation speed decreasing (reduces the force of spheronisation
2. wet amss/ extrudate cohesive strength increases (increases mechanicam strength)

Question 26

what happens when cohesive forces ~ forces during spheronisation

Answer 26

round, narrow size distribution, leading to:

Question 27

what happens when cohesive forces > forces during spheronisation

Answer 27

spheronisation speed increase, leading to:

• breaking and rounding of extrudate
• particle size dereases
• causing surface area to increase
• hence greater cohesivity

Question 28

importance of packability of component particles

Answer 28

• influences the spheroid formation

- dependent on particle size, size of distribution of its component, and force exerted during wet processing

Question 29

functionality of spheronsation aid dependent on

Answer 29

• in process particle size

- overall matrix cohesiveness during wet processing steps of extrusion-spheronisation

Question 30

cohesivity is important for pelletisation but:

Answer 30

• cannot have migratable stickiness (eg. use PVP or HPMC or melt)
• use immobile adhesive particles (micronised powder , MCC)

Question 31

what does migratable stickiness do

Answer 31

make a process less robust, for controlling final product size (eg. in melt pelletisation)

Question 32

examples of direct pellisation

Answer 32

1. fluid bed layering
2. balling process
3. one-pot rotary process (expensive)