L53: tablet coating and drug release Flashcards
(20 cards)
What is omeprazole?
A proton pump inhibitor that is unstable in acidic environments
Omeprazole is absorbed in the small intestine but can be broken down in the stomach due to its acidity.
How can the breakdown of omeprazole in the stomach be prevented?
By using enteric coating
Enteric coating protects the drug from acidic conditions.
What is tablet coating?
Application of a coating material to the exterior of a tablet to confer beneficial properties
This includes protection from the environment, taste masking, and ease of swallowing.
What are the three main types of coatings in use?
- Film coating
- Sugar coating
- Press coating
Why coat tablets?
- Protection from light and moisture
- Masking unpleasant tastes
- Easier to swallow
- Rapid identification
- Imparting enteric or controlled-release properties
What is sugar coating?
Sealing of tablet core to prevent entry of water, followed by sub-coating, smoothing, coloring, polishing, and printing
Sugar coating often involves the use of shellac or cellulose acetate phthalate.
what is film coating?
*spraying of a thin polymer around the tablet core
What are the key differences between sugar coating and film coating?
- Sugar Coating: Multistage process, 30-50% weight increase, rounded appearance
- Film Coating: Single stage, 2-3% weight increase, not as shiny
what are some problems with coating?
*picking/chipping
*roughness
*sticking
*film peeling
What is enteric coating?
Protects the tablet core from disintegration in the acidic environment of the stomach
*prevents attack on drugs unstable at low pH
*protects stomach from irritation
*absorption later on in the GI
*taste masking
It is used for drugs that are unstable at low pH, to protect the stomach, and to facilitate absorption.
What are pH-sensitive polymers?
Polymers that are insoluble in aqueous media at low pH but become soluble at a specific higher pH
Examples include cellulose acetate phthalate (CAP) and polyvinyl acetate phthalate (PVAP).
what are examples of enteric polymers for direct film-coating?
- Cellulose acetate phthalate(CAP)
- polyvinyl acetate phthalate(PVAP)
- polymers have free carboxylic acid groups
- insoluble at low pH
What is the typical composition of enteric coatings?
- Cellulose acetate phthalate (CAP): 5.0% w/w
- Glyceryl triacetate: 1.0% w/w
- Isopropyl alcohol: 17.0% w/w
- Dichloromethane: 68.5% w/w
- Water: 8.5% w/w
What are multi-particulates?
Spherical particles used for controlled and delayed release oral formulations
* particles can either be filled into capsules or tableted
* each pellet is coated so its easier to control
* they have good stability and flow properties
They can be filled into sachets, encapsulated, or compressed into tablets.
what are some types of multi-particulates?
- extruded/spheronised granulates
theyre produced in modified granulating equipment
What are the advantages of multi-particulates?
- More consistent GI transit
- Less likely to suffer from dose dumping
What are the disadvantages of multi-particulates?
- Difficult control of membrane characteristics
- Hard to retain in the upper GI tract
What are the drug release mechanisms from multi-particulates?
- Diffusion: when in GI tract, water moves in and dissolutes drug inside and allows diffusion across coat
- Osmosis: as water enters, osmotic pressure builds up forcing drug out
- Erosion: degrade with time
why should enteric coated tablets not be taken with antacid?
- it increases the pH of gastric fluid which could cause the coat to dissolve in the stomach
What are Multiple-unit pellet systems (MUPS)?
Tablets that contain enteric-coated particles, allowing for controlled release
* methacrylic acid copolymers appear best suited to enteric coating the particles that make up MUPS
MUPS tablets can be broken and dispersed without chewing or crushing the particles.
