D6 What holds tablets together and excipients Flashcards
(53 cards)
where does the compression of powders into tablets occur?
occurs in tableting machine (press)
list the tableting compression stages
- filling of die
- particle rearrangement
- elastic deformation at points of contact
- fragmentation / plastic deformation
- bonding
- plastic deformation of the solid body
- decompression and ejection
explain the stage of tableting compression: filling of die
- powder flows uniformly down and die is filled to its volume
- glints are important here for promoting good flow
explain the stage of tableting compression: particle rearrangement
pressure starts being applied and loosely packed powders rearrange to expel air between particles and arrange more closely packed together
explain the stage of tableting compression: elastic deformation at points of contact
- as more pressure is applied, the particles start to elastically deform
- particles are coming together like people do in a crowd
- if pressure stopped being applied, particles would return to their original shape
explain the stage of tableting compression: fragmentation and / or plastic deformation
- pressure is continued to apply and particles fragment into small pieces or just plastically deform depending on the particle’s properties
- either of the above can happen or both. if there are different particles in the powder mixture
explain the stage of tableting compression: bonding
- even more pressure leads to particles bonding together
- binder is the important excipient for this stage and for promoting bonding of particles together
which excipients are important for decompression and ejection of tablets
- lubricants
- similar to butter in a cake tin
what excipient is important for bonding in tableting?
- binder
- promotes bonding of particles together
what is the difference between elastic deformation and plastic deformation?
- elastic deformation is reversible and temporary
- plastic deformation is not reversible or temporary
what is capping pressure?
- when compressing powders, there will also be air inside that can’t be expelled
- if you have too much hair or you compress the tablets too much to be very dense, the air expands after compression and breaks the tablets
what is the relationship between water and hard tablets?
- harder for water to penetrate and disintegrate harder tablets because the particles are packed very densely and water can’t penetrate gaps
what differences between tablets of the same drug can affect bioavailability?
same drug made into two tablets at different pressures (different hardness)
state the 3 theories for how tablets are held together
- mechanical theory
- intermolecular theory
- liquid surface film theory
describe and explain the mechanical theory of how tablets are held together
- mechanical interlocking of particles
- particularly relevant when powder particles undergo plastic deformation during compression
- molecules assume such a shape that they interlock together and do not come apart when pressure is removed
describe and explain the intermolecular theory of how tablets are held together
- contact between new surfaces close enough so that Van Der Waals forces can act
- particularly relevant when powder particles fracture during compression
what causes the liquid surface film theory?
surfaces melt (or dissolve in residual moisture) under applied pressure and upon the release of the pressure the melted (dissolved) material crystalline forming connections between the particles
where is pressure felt more in the liquid surface film theory? what does this mean?
- pressure is felt more at the points where particles touch each other
- this means you do not feel pressure equally everywhere
what 2 things can high pressure at points of contact do in the liquid surface film theory?
- surface can melt at touching points so when pressure is removed, molten bridge remains and particles stick together
- residual moisture that is present in powder turns into water at points of contact and dissolve a bit of each particle so the solution of dissolved material makes bridges between the touching particles and they stick together
what are excipients?
pharmaceutical substances other than the active drug or prodrug which has been appropriately evaluated for safety and are included in a drug delivery system
state 4 things that excipients can do
- aid processing of the system during manufacture
- protect, support or enhance stability, bioavailability or patient acceptability
- assist in product identification
- enhance any other attribute of the overall safety and effectiveness of the drug product during storage and use
what 3 excipients could be used to provide essential manufacturing technology functions?
binders
glidants
lubricants
what 2 excipients can be used to enhance patient acceptance?
flavours
colourants
what excipients could be added to provide aid in product identification?
colourants
