Tablet Coating Flashcards
What are the reasons for coating?
Enhance aesthetic appeal and brand image Masks unpleasant taste and odour Enables product to be easily swallowed Reduces frequency of drug dosing Improves product stability Increases shelf life Facilitates product ID during manufacture and prevent wastage during packing and handling Modifies drug release characteristics Provides enteric release properties for release in the intestinal tract.
What is coating?
The application of a coating composition to a moving bed of substrates with the concurrent use of heated air to facilitate th evaporation of the solvents
How does tablet coating improve product stability ?
by protecting the tablet against deterioration from environment, sunlight, temperature variations, moisture, environmental gases etc.
How does tablet coating modify drug release characteristics?
Can achieve a wide range of drug release including
Immediate release
Specific release
Sustained release
Controlled release
As well as targeted drug delivery properties
What are the 3 general types of equipment used in tablet coating?
Standardised coating pan
Perforated coating pan
Fluidised bed (air suspension) coated
What is the standard coating pan?
Consists of circular metal pan mounted angular lay on a stand.
Heated air is directed into the pan and onto the tablet surface and exhausted by the ducts positioned throughout the front of the pan.
The coating solutions are applied onto the tablet by spraying the material onto the rotating tablet bed.
What is a perforated pan?
This consists of a perforated or partially perforated drum which is rotated on its horizontal axis in an enclosed housing
E.g. Accela-Cota and Hi-Coater systems
What are the main components of a perforated pan?
Air supply Exhaust Spray Perforated coating pan Exhaust plenum Tablet bed
What is the principle of fluidised bed (air suspension) systems?
Suspend the tablets in an upward moving stream of air so that they are not in contact with each other
How is fluidisation of tablets achieved?
In a columnar chamber by the upward flow of drying air.
The airflow is controlled so that more air enters the centre of the column.
This causes tablets to rise in the centre.
The movement of tablets is upward through the centre of the chamber no then they fall toward the chamber wall and move downward to reenter the air stream at the bottom of the chamber
What are the main components of the fluid bed Coater?
ExHaust air duct Coating chamber Funnel like modification Support screen Air atomizing nozzle Fluidizing air supply
What are the types of coating?
Sugar coating Film coating (including enteric film coating allowing pH controlled drug release in the intestines which can be adjusted by a combination of polymers and coating thickness).
What are the advantages of sugar coating?
Elegant Attractive High glossy appearance Inexpensive raw materials Widely accepted with few regulatory problems Wide consumer acceptability
What are the limitations of sugar coating?
Tedious and time consuming process (~3-5 days per batch)
Requires expertise of highly skilled technician
Tablet size and weight almost double
There is batch to batch variability even within same batch.
Costly in terms of space, equipment, packaging, shipping
Potential microbial growth and contamination
Hygroscopic
Not as convenient to swallow.
What are the main steps for sugar coating?
Sealing
Sub coating
Smoothing colour coating
Polishing
Why is the sealing step required?
To prevent moisture penetration into the tablet core.
Without a sealing coat, the over wetted tablet would absorb excess moisture resulting in tablet softening or disintegration, affecting the stability of the final product
What are the excipients used in sealing?
Shellac
Zein
HPMC
CAP
Why is dusting powder (talc) used in sealing?
To minimise the risk of clumping and twinning and sticking of tablets to each other .
Why is subcoating conducted?
To round the tablet edges and build up the code weight.
What happens in subcoating?
The tablet weight increases by 50%-100%
This step consists of alternatively applying a sticking binder solution to the tablets followed by a dusting of subcoating powders followed by drying.
What are the dusting powders used in the subcoating step?
Talc Starch Kaolin CaSO4 CaCO3