Flashcards in Greco Lecture 6: Compression and Drying Deck (20):
What is drying and how does the process work?
1. Drying is the process by which a liquid is removed from a wet solid
2. This is done by applying heat to wet material which causes the solvent to evaporate and leave the material
What are the two advantages of drying?
Increases the stability and improves flowability
What are the different forms of driers that are available to use?
1. Tray drier
2. Fluidised bed drier (main one like the one in practical)
3. Vacuum oven
4. Microwave radiation
5. Spray drier
6. Freeze drying
What is process of tablet formation using the tableting machine?
1. Filling: Foot of hopper shoe places the material between the punch and the die
2. Compression: Punch compresses it
3. Ejection: tablet is formed
In terms of the physics of compression, what does Fa, Fb and Fd stand for?
1. Fa: Compression force
2. Fb: Reaction force
3. Fd: Attrition force
When Fd is close to zero nearly at equilibrium, what does this mean tablet composition and pressure?
1. It means that the pressure is the same from the top as well as the bottom
2. Leads to similar compaction throughout the whole tablet
What are the two main frictional forces that are found when producing a tablet and how can reduce both of them?
1. Friction between particles:
Glidants are used to reduce this effect
2. Friction between material and die wall
Lubricants are used to reduce this effect
What are the effects on the content with compression?
1. Pore size decreases
2. Pore number decreases
3. Mechanical strength increases
4. Tendency for the tablet to disintegrate decreases
What is porosity?
The percentage of voidage of the powder bed
How do you calculate porosity of a tablet?
1. Volume of pores/ Volume of bulk
2. (Volume of bulk - Volume particles)/ Volume bulk
3. 1 - (Volume particles/Volume bulk)
What occurs during compression?
1. Repacking of particles
2. Elastic or plastic deformations (contact points)
3. Powders or granules fragmentation and formation of new surfaces
4. Cohesion between particles
5. Elastic or plastic deformation at solid points
6. Tablet ejection
What is the purpose of disintegration and dissolution?
1. Get the drug in solution in the GI tract
3. Drug in the blood
4. Therapeutic effect
What is the correlation between disintegration time and plasma concentration of a drug?
The lower the disintegration time, the higher the plasma concentration of the drug
What is the order for different types of tablets in terms highest disintegration time to lowest?
1. Gastro resistant tablets (2 hours)
2. Coated tablets (1 hour)
3. Film coated tablets (30 minutes)
4. Uncoated (15 minutes)
What are the objectives of tablet coating?
1. Masking taste
2. Alter dissolution and disintegration time
3. Physically or chemically protect ingredients
4. Add another drug into the coating to allow for sequential drug release or due to incompatibilities
5. Favour swallowing
6. Improve mechanical strength of tablet
What are the steps that must be completed prior to coating?
1. Resistance to abrasion and rupture
2. Shape (spherical or round)
3. Appropriate chemical-physical properties
What are the steps that are involved in sugar coating a tablet?
1. Sealing of tablet core
What are the advantages of film coating over sugar coating?
1. Less thickness
2. Better stability and mechanical strength
3. One step process
What does the film coating suspension contain?
1. Polymer: ethers of cellulose (e.g. Hydroxypropyl methylcellulose)
2. Plasticers (PEG and oil)
3. Colourants (Iron oxide pigments and titanium dioxide)
4. Solvents (organic solvents but now is usually water)