Tablets: Compression and Compaction

Question 1

What characteristics should a diluent have?

Answer 1

• inert
• hydrophilic
• non-hygroscopic
• biocompatible
• cost effective
• good flow properties

Question 2

What are the three steps for direct compressed tablets?

Answer 2

• particle size reduction
• mixing
• tablet press

Question 3

What are the excipients used in compressed tablets?

Answer 3

• filler
• binder
• disintegrant
• glidant
• antiadherent
• lubricant - added as close to tabletting process otherwise it will coat other excipients
• flavour, sweetener and colouring agent

Question 4

Why would disintegration be faster for direct compression?

Answer 4

no granules

tablet to fine powder particles

Question 5

What is there an increased risk of in compressed tablets?

Answer 5

segregation caused by wide size distribution

Question 6

What is compression and compaction?

Answer 6

compression: reduction of bulk volume under applied force
compaction: formation of a solid with defined geometry and strength

Question 7

What does compression and compaction consist of?

Answer 7

• re-arrangement: less porosity
• deformation: moderate pressure causes deformation and densification and high pressure causes fragmentation
• bonding: formation of interparticular bonds

Question 8

What is the yield point of powders and what is it effected by?

Answer 8

the point inbetween region of elastic deformation and plastic deformation

• polymorphism
• salt form
• moisture content
• particle size
• compression rate

Question 9

What happens to granules during rearrangement and deformation?

Answer 9

rearrangement: limited impact for granules
deformation: densification ; loss of intragranular pores

Question 10

What is more likely in granules attrition/erosion or fragmentation?

Answer 10

attrition/erosion

Question 11

What can compressibility be assessed by?

Answer 11

• look at properties of ejected tablets
• look at compression/decompression events

Question 12

What does bonding result from in dry powders?

Answer 12

• solid bridges
  
  • mixing at interface between solid, creates continuous solid phase
  • more likely for tablets with a low porosity
• adsorption bonding
  
  • result of reduced inter-particular distances
• mechanical interlocking
  
  • interparticular locking of irregularly shaped rough particles

Question 13

What does high compactability lead to?

Answer 13

tablets that have

• high resistance to fracture
• low tendency to cap (fracture of bottom or top layer) or laminate (separated into two layers in the middle)

Question 14

How does compression affect compactability in solid particles?

Answer 14

• fragmentation and plastic deformation are associated to increased tablet strength
  
  • fragmentation lead to formation of smaller particles and decreased porosity - interparticular bonds formed
  • plastic deform: increased contact between particles - interparticular bonds formed
• elastic deformation leads to low tablet strength
  
  • higher capping/lamination propensity
• impact of size; smaller tablets lead to increased tablet strength

Question 15

How does compression affect compactability in granules?

Answer 15

• impact of granulation process
  
  • shape, size porosity, strength
• impact of properties of primary powder particle
• impact on granule composition
• presence of a binder
  
  • binders help bond strength = improved compactability = imporoved tablet strength

Question 16

What are issues during tabletting?

Answer 16

• unit process efficiency
• flowability
• compressibility and compactability
• friction and adhesion