pH and tablet coating Flashcards
1
Q
Why coat tablets?
A
- protection from environmental factors- light, moisture
- Mask a bitter/unpleasant drug taste
- Ease of swallowing
- Coatings can mask batch differences in tablet colour
- Coatings may be coloured allowing easy identification
2
Q
Types of tablet coatings
A
- Film- modified release includes enteric coating
- Sugar- immediate release
- Compression
Enteric coating are used to prevent the tablet disintegrating in the stomach.
3
Q
Describe FILM COATING
A
- Thin film sprayed onto the tablet on a rotated, mixed tablet bed
- Capsules, pessaries, granules
- Typical constituents:
- Polymer
- Vehicle/solvent
- Plasticiser- make polymer flexible
- Pigments
4
Q
What polymers are used for film coating?
A
- Cellulose: Hydroxyl (OH) group of cellulose are esterified to prepare polymers that are better suited to film coating.
- Cellulose ethers: Hydroxypropyl methylcellulose
5
Q
Cellulose acetate phthalate
A
- Enteric film coatings are intended to be stable in the strongly acidic stomach environment
- CAP is a ph-sensitive cellulose derivative
6
Q
What are the other non-cellulose derivative polymers used in enteric coating?
A
- Methacryclic acid copolymers:
- contains an acidic functional group
- available as an aqueous dispersion
7
Q
What ingredients are in an enteric coating mixture?
A
- CAP
- Glyceral triacetate- plasticiser
- Isopropryl alcohol
- Dichloromethane
- Water
8
Q
MUPS
A
- Multiple Unit Pellet System
- Enteric coated particles compressed into a tablet
- The polymer coat needs to be more flexible because of the compression forces that are applied in the tableting process
- MUPS work on the same principle as EC granules
