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Science of medicine > Tabletting > Flashcards

Tabletting Flashcards

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1
Q

what are tablets

A

single dose of compressed powder

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2
Q

why are tablets good

A

small, stable (no water and coating blocks light) , easy to identify with its colour/shape, taste masked by coating, packaging can be made water resistant

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3
Q

common shapes of tablets

A

round, oval, capsule
flat, bevelled, convex

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4
Q

name the stages of tablet manufacturing process

A

powder mixture of drug and excipients, wet/dry granulation then granules or direct compression, basing, compression into tablets, de-dusting, tablet coating, packing

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5
Q

what is basing

A

dry mixing in lubricant and more disintegrant if needed

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6
Q

list the 3 batch sizes

A

lab scale- formulation design stage
pilot scale- clinical trials
full scale industrial batch

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7
Q

what are excipients

A

inactive ingredient in drugs

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8
Q

what is the aim of a powder mixture

A

uniformly mixed, flows well, doesnt separate

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9
Q

what processes can cause powder separation and how

A

-transport, mixing, tablet machine vibration
-causes smaller particles to fall through the spaces between the bigger ones
-caused by difference in particle shape size and density

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10
Q

consequences of separation

A

variability in dosage which can lead to under or overdosing, uneven distribution of drug/excipients eg. some parts of the drug will have more disintegrant so it will be released faster than others

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11
Q

what is the aim of granulation (powder binded together forms granules)

A

prevent powder separation

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12
Q

describe wet granulation and its variables (know the diagram)

A

bowl, detector probe, rotating impeller and chopper, solution of binding agent sprayed onto powder, wet granules are dried then sieved

variables- mixing time, rate of adding liquid, speed of impeller and chopper, internal environments

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13
Q

stages of granule formation

A
  1. wetting and nucleation- small aggregates form from particles
  2. consolidation and coalescence- granules grow as aggregates combine

limits to granule growth- amount of fluid, breakage, attrition

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14
Q

how to detect granulation end point

A

trials or detector probes

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15
Q

what happens if you stop before the granulation end point

A

aggregates are under-wet, too fragile for drying process

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16
Q

what happens if you stop after the granulation end point

A

aggregates are over-wet, dry lumps are hard to compress

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17
Q

what is granulation end point

A

maximum amount of good granules

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18
Q

describe dry granulation (ribbon type) and its variables

A

hopper, screw feeder to ensure constant supply, powder is compacted between roles producing ribbons of compressed powder, ribbons are broken up then sieved to make granules

variables- feed rate, roller speed, moisture content of powder

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19
Q

difference between granules formed from wet and dry granulation

A

wet- particles glued together with binding agent (water soluble polymer)

dry-particles held by compression at points of contact

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20
Q

advantages and disadvantages of direct compression

A

advantages- saves money (no granulation equipment), saves energy, saves time, faster development time and less processes

disadvantages- mixture must flow, powder mix cant segregate, needs special excipients, hard on industrial scales

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21
Q

how are tablets compressed

A

using a rotary press or die and lower/upper punches

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22
Q

granule requirements for a good tablet to be formed

A

good flow- large round particle, fills die accurately to make uniform weight and dose

compactable powder mix- lots of inter particulate bonding, produces strong tablets, prevents capping/breaking

no separation- ensure composition of tablet stays the same, prevents deficiency in one component

right amount of lube- tablets can be ejected with minimum force, prevents them breaking due to high ejection pressure, too much can lead to weak tablets, machines struggles to eject if too little

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22
Q
A
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23
Q

why do tablets need the right amount of lubrication

A

to ensure tablets are ejected with minimum force, too much can break the tablets due to high ejection pressure, too little can be hard to eject, too much will have too little interparticulate bonds and form weak tablets

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24
Q

why do powders need to resist separation

A

ensure tablet composition stays the same during production, ingredients may separate due to machine vibrations, tablets can become enriched or deficient in one component

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25
Q

why do powders need to be compactable

A

so strong/hard tablets can be produced, prevents lamination/capping/breaking, wont survive coating if its weak

26
Q

how do powders compact

A

inter-particulate bonding

27
Q

why do powders need to have good flow

A

ensures die fills accurately to prevent variation in weight and dose

28
Q

main stages of tablet compression cycle (learn diagram)

A
  1. dye filled with powder/granules
  2. upper punch applies force down to make tablet and withdraws
  3. lower punch ejects tablet
29
Q

why doesnt the tablet fit the die anymore after its been ejected

A

elastic expansion

30
Q

types of internal bonds formed during tabletting

A

interlocking, melting at contact points, molecular bonding (H bonds, VDW)

31
Q

types of defects in tablets

A

laminations- horizontal cracks due to over compression

capping- top comes off due to lamination

chipping- edges chipped

picking/sticking- surface pitted because material stuck to punches

stress cracks- cracks due to elastic expansion after compression

friability- edges erode, turns to powder

32
Q

examples of problems in formulation

A

lots of elastic ingredients- tablet defects
poor compression
low mp- sticks to punch
drug reacts with excipients
wrong amount of lubricant

33
Q

types of tablet machines

A

single punch- 50 tablets per min
rotary- multiple punches, 20,000 per min, pilot and full scale manufactures
compaction simulator- single punch, one at a time

34
Q

tablet coating process

A

uncoated tablet, none/sugar/film/compression coating, cleaning and polishing, packing

35
Q

sugar coating process (diagram) and its variables

A
  1. coating liquid poured onto tablet bed at intervals
  2. pan rotates and coats tablets evenly
  3. hot air blown to dry coat then more liquid is added, thin layers produce a thick sugar coat

variables- rate of liquid added, pan rotation, air flow, air temperature

36
Q

film coating process and variables (diagram)

A
  1. coating liquid continuously sprayed onto tablet bed
  2. drum rotates and spreads liquid over tablets
  3. hot air goes in and liquid evaporates and leaves a solid polymer film

variables- spray rate, drum rotation speed, temperature, air flow

37
Q

what does film coating liquid contain

A

polymer latex- no organic solvents
plasticiser- helps particles coalesce
colour- fine suspension lake
surfactant- helps spread liquid
separating agent- tablets become sticky during drying

38
Q

compression coating process (diagram)

A
  1. weak tablet formed
  2. coating formulation compressed onto it
  3. double compression makes tablet stronger
39
Q

why are bulking agents needed

A

make tablets big enough to swallow

40
Q

examples of some bulking agents

A

sugars, minerals, polymers
glucose, talc, starch, microcrystalline cellulose

41
Q

desirable characteristics of bulking agents

A

good compactability, good flow, chemically compatible with drug, cheap

42
Q

why are compression aids needed

A

make strong tablets when ingredients are poorly compactible

43
Q

example of a compression aid

A

microcrystalline cellulose

44
Q

desirable characteristics of compression aids

A

excellent compactability and plastically deforms so it flows so it maximises bonding in tablets

45
Q

structure of cellulose

A

linear polymer of glucose bonded together by glycosidic bonds, forms layers connected by hydrogen bonding, chains slip under pressure and H bonds break and reform

46
Q

issues with MCC as a compression aid

A

more expensive than bulking agents, hygroscopic so needs to be stored in a dry place, doesnt flow well when damp

47
Q

what is MCC

A

microcrystalline cellulose

48
Q

what is the function of disintegrants and common examples

A

accelerate the break up tablet when exposed to fluid, releases drug for dissolution

examples- starch, MCC, sodium starch glycollate

49
Q

mechanism of disintegrants

A

swelling- disintegrant sweels and tablet bursts apart eg. starch

wicking- water drawn in through network of disintegrant fibres and soluble materials inside tablet dissolve eg. MCC

effervescent material- make CO2 gas to break tablet

50
Q

why is an insoluble disintegrant good

A

tabletting part 3 page 22 idk

51
Q

problems with disintegrants

A

elastic so weakens tablets, less effective if wetted or high humidity, superdisintegrants interact with drugs to form salts

52
Q

why are lubricants needed and common examples

A

lubricates ejection of tablet from die after compression

eg. magnesium stearate, SDS, stearic acid

53
Q

mechanism of lubricants

A

particles are stacks of flat, waxy crystals which can slide over each other

54
Q

issues with magnesium stearate as a lubricant

A

hydrophobic, makes drug water repellent which reduces drug dissolution, slows drug release, weakens inter-particulate bonding during compression so weaker tablets are formed

55
Q

what is the function of flow aids and common examples

A

increases flowability of power/granules, good flow is important

examples- colodial silicon dioxide

56
Q

mechanism of flow aids

A

coats surface of particles, adsorbs surface moisture so they dont stick together

57
Q

issues of flow aids

A

dust hazard

58
Q

types of tablets

A

chewable/dispersable, immediate release, delayed release, extended release, tablets for special routes

59
Q

types of chewable tablets

A

effervescent tablets, tablets that dissolve rapidly in mouth

60
Q

how do dispersible tablets release drugs

A

dissolve in water/saliva, solution/suspension of drug, drug solution in GI tract, diffuses through gut wall and bloodstream absorbs drug molecules

61
Q

where are most drugs absorbed

A

upper small intestine

62
Q
A

Science of medicine (7 decks)

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