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Solid > Pelletization > Flashcards

Pelletization Flashcards

1
Q

advantages of using spheroids as a multi-unit dosage form (in terms of therapeutic)

A
  • minimise local irritation
  • maximise absorption/ bioavailability
  • less susceptible to dose dumping
  • reduction in GER
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2
Q

advantages of using spheroids as a multi-unit dosage form (in terms of technological)

A
  • superiority for coating (able to coat well)
  • uniformity in packing (all are same sizes)
  • spherical in shape
  • good flowability
  • low friability (doesnt break easily)
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3
Q

pellets for multi-particulate dosage forms is used for what systems?

A

customised/ modified release system

- sustained-release action

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4
Q

4 diff methods of pelletization techniques

A

direct pelletization

  • aq-based pelletisation
  • melt-based pelletization

pelletization through extrusion step

  • extrusion-spheronisation
  • hot-melt extrusion

layering onto starter seeds

  • powder layering
  • solution layering
  • suspension layering

formation of droplets

  • spray drying (in lec7)
  • spray congealing (in lec7)
  • cryopelletization
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5
Q

3 methods of direct pelletization

A

(1) fluid bed layering
- pelletization by layering onto starter seed
- successive coats on the seed particles wo agglomerative growth

(2) balling process
- a layering process, to produce nonpareils

(3) pelletization in rotary processor
- ‘one-pot’ pelletization
- spray agglomeration media directly onto powder mass in a spheronizer to from pellets
- pellets formed in situ
- change spray media into coating media after introducing drying air into chamber

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6
Q

why extrusion-spheronisation is the method of choice for producing pellets

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

ease of operation
high throughput with low wastage
very efficient

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7
Q

steps for extrusion-spheronization process

A

(1) dry blending
(2) wet massing
(3) extrusion
(4) spheronization
(5) drying
(6) coating (coat for sustained release)

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8
Q

what happens in the extrusion step?

A

moistened powder mixture passed through screen aperture to form extrudates

extrudates: jagged w regular spaced shark-skinned protuberances, high-density, cylindrical

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9
Q

for the extrusion step, how do we determine the screen aperture size?

A

screen aperture size approx the desired size of pellets

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10
Q

what happens in the spheronization step?

A

spheroids are formed where extrudates are broken into uniform length and rounded w a rotating frictional plate

rounding due to a ‘rope-like’ motion
shaping is due to plastic deformation (ability to be mold)

pellets similar size to screen aperture size, highly spherical and narrow size distribution

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11
Q

when do we know we have gotten out desired pellet size and shape (spherical)?

A

using real-time imaging: size distribution becomes narrow (graph becomes narrow and sharp peak formed) (slide 22)

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12
Q

4 different mechanism of pellet formation (theories of how pellets are formed)?

A

(1) Rowe
(2) Baert and Remon
(1) and (2) was theorised based on plasticine

(3) Liew
(4) Koester and Thommes
(3) and (4): fragments of diff size come together and build up

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13
Q

what is required for extrusion to take place?

A
  • cohesive

- plastic wet mass with inherent fluidity and self-lubricating properties

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14
Q

what is required for spheronization to take place

A
  • extrudates with sufficient plasticity
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15
Q

basic formulation of forming pellets?

A
  • pelletization aid
  • drug
  • filler
  • moistening liquid
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16
Q

difference bet granulation and spheronization

A

spheronization: objective is to make a highly spherical particle
granulation: not this objective

other than this diff, spheronization and granulation are similar

17
Q

why is Microcrystalline cellulose (MCC) a good pelletisation aid?

A
  • good binding property
  • good cohesiveness
  • larger surface area (low s.a. to vol ratio); microfibrous
  • high internal porosity
  • prepares highly spherical granules of narrow size distribution and with desired mechanical properties
18
Q

function/ ability of MCC as a pelletization aid

A

molecular sponge model

(1) Extrusion
- MCC absorbs water: forms cohesive yet plastic wet mass
- helps in binding and lubrication

(2) helps in binding and lubrication during spheronization
- increase surface plasticity
- helps in rounding extrudates into pellets

crystallite gel model

(1) MCC broken down into single crystallites to form crystallite gel and immobilise the liquid
- under pressure/extrusion, MCC release water

19
Q

other pelletization aids, other than MCC

A
  • cross-linked polyvinyl pyrrolidone (PVP) - v successful
  • powdered cellulose
  • hydroxypropyl methylcellulose (HPMC)/ Hypromellose
  • Hydroxyethylcellulose
  • chitosan
  • carrageenan
20
Q

what is considered a good pellet?

A

(1) well-formed extrudates
(2) breaks into short lengths
(3) rounds quickly

21
Q

how to ensure pellets formed a highly spherical?

A

particles are 1/6-1/8 of desired pellet size

  • smaller particles produce agglomerates that are more spherical
22
Q

how do we know how much moistening liquid is to be added to make the pellet?

A

using a mixer torque rheometer (MTR), where moistening liquid (water) added to powder mass

rheological proflie of moistened powder mass is obtained

results:
use 80-90% of Tmax as a marker of how much water to add and how much torque to apply
(Tmax usually is when the capillary form is made) (slide 33)

23
Q

what is the ideal forces seen in spheronization for a successful pelletization? and what pellets do we see?

A

cohesive force approx/equal to forces during spheronization

  • round; narrow size distribution
24
Q

what happens when cohesive forces are lesser than the forces during spheronization?

A

irregular shaped pellets; wide size distribution (not ideal)

25
Q

what alterations can we do when we have cohesive forces are lesser than the forces/ pellets become irregular shaped?

A

(1) reduce the spheronization speed

(2) increase the wet mass/extrudate’s cohesive strength by:
- repeating extrusion step
- reduce component particle size (increase s.a.)
- widen size distribution of components

26
Q

what happens when cohesive forces are greater than the forces during spheronization?

A

pellets become elongated

27
Q

what alterations can we do when we have cohesive forces are greater than the forces/ pellets become elongated?

A

increase spheronization speed

28
Q

packability influences spheroid formation. what does packability depend on?

A
  • particle size (small)
  • size distribution (wider)
  • forces exerted during wet processing (wet massing step)
29
Q

3 things that makes spheronization a success?

A

(1) particle/component size (small), and overall matrix cohesiveness during wet processing steps
(2) good packability
(3) optimal balance of forces (cohesive forces approx/equal to forces applied during spheronization)

30
Q

ideal distribution for moistening mass (wet prcoessing step) for pellet formation

A

(1) *wide size distribution–> w moistening liquid: well packed, strong pellets formed (best)
(2) small particles –> w moistening liquid: well packed, strong pellets (but can trap air and require large mechanical strength for packing) (ok)

(3) not ideal:
coarse particles –> w moistening liquid: loosely packed; friable pellets

31
Q

cohesivity is important for pelletization. but what is something that cohesivity can’t have

A

cannot have migratable stickiness (mass keeps growing)
- seen with the use of PVP/ HPMC or melt; (PVP/ HPMC are soluble in water)

  • use immobile adhesive particles (e.g. micronised powders, MCC - both are insoluble)
32
Q

why is migratable stickiness undesirable

A

makes a process less robust for controlling final product size

  • particles continue to grow
  • see in melt pelletization
33
Q

summary: what are the critical attributes for successful pelletization?

A
  • nature of component particles

- amount of moistening liquid

34
Q

summary: main method for making drug containing pellets in the pharma industry

A

extrusion-spheronizarion

35
Q

summary: why understanding the science of spheroid formation is impt

A
  • ensure good quality pellets are made for use as multi-particulates for drug delivery
36
Q

why everywhere is a sphere?

A
  • minimisation of energy: reduction of friction during motion

Solid (16 decks)

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