Film coating Flashcards
Reasons to apply coating
1) Improve appearance
2) Taste making
3) Stability (moisture, o2, and light barriers)
4) To confer mechanical strength
5) To facilitate handling of the tablets on production lines
6) Modify drug release
Types of coating
Sugar coating
Film coating
Other coating methods (Compression/ electrostatic and gelatin)
Fim coating
1) Immediate release
2) Modified release ( enteric, sustained)
Component in a film coat
Film former Solvents Plasticisers Colourants Anti- tacking agents
Polymers of immediate release film coating
Hydroxypropyl methycellulose (HPMC) Methylcellulose (MC) and hydroxypropyl cellulose (HPC) Vinyl derivatives (PVP and PVA and vinyl acetate)
Polymers for modified release film coating (enteric)
Metharcylic acid copolymers
Cellulose based polymers (cellulose acetate pthalate)
Polyvinyl derivatives (polyvinyl acetate pthalate)
Reasons for using enteric coated tablets
1) Prevent degradation of acid sensitive API
2) Prevent irritation of stomach and certain drugs
3) Delivery of API into specific site of the intestine for localised disease
How does enteric coating work
1) Contains COOH group in the polymer structure
2) Unionized and insoluble at the low pH of the stomach
3) pH dependent dissolution and drug release
Polymers for modified release sustained release
- Ethyl cellulose
- Polymethacrylate polymers (pH dependent Eudragits)
What are plasticizers
Small molecules that interpose themselves on a molecular stage between polymer strands.
How do plasticizers work
- Decrease friction between film forming polymers
- Decrease glass transition temperature
- Increase film flexibility and decrease film brittleness
Examples of plasticizers
Polyethylene glycol (PEG)
Organic esters
Oil/glycerides
How do Anti tacking agents work
Prevent stickiness during coating
Examples of anti tacking agents
Talc (10-50%) Glycerol monoesterate (GMS 2-5%)
Use of colorants
Provide elegant appearance
Some have light protective properties.
Examples of colorants
Iron oxide pigments
Titanium dioxide
Aluminium lakes.
Film coating process (4)
1) Spray - coating liquid (solution and suspension)
2) Deposit - liquid droplets onto the cores
3) Film formation - a thin layer of film is formed due to solvent evaporation
4) Drying - Further removal of the solvent leaves to dry film around the core
Examples of film coating
Pan coater Fluidised bed coater Particle coalescence Compression coating Electostatic coating Vacum film coating Sugar coating
Pan coating
Pan speeds keep tablet tumbling and then sprayed, via inlet and outlet air temperature
Temperature cant be too hot - solution dries before it hits the tablet
or too cold - evaporation does not occur from the tablet surface.
Sugar coating
1) Sealing
2) Sub - coating
3) Smoothing
4) Colouring
5) Polishing
6) Printing
