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Film Coating Process of Tablets in Pharma Manufacturing


Learn about Film Coating process and difference between Aqueous and Solvent Film Coating.

Film Coating

·  Minimal weight gain (2-3% as opposed to 60-80 % for sugar coating)

·  Coat is less likely to affect disintegration

·  Single stage process an so generally quicker

·  Easy to automate (less reliance on skilled operator / easier to meet GMP requirements of SOPs, validation etc) Maintains original shape of the core & allows for embossing

·  Expensive equipment & plant requires large space

·  High installation & energy costs

Film Coaintg

Aqueous vs Solvent Film Coating

•  Solvent based coating solutions / suspensions (e.g. alcohols, methylene chloride)
 rapid drying time due to inherent volatility
 can be applied to moisture sensitive products
 operator safety issues
 requires modification to equipment and facility (flame-proofing / intrinsically safe)
 environmentally responsible disposal is expensive (solvent recovery)
 can impart taste / smell to the product
•  Aqueous based processes are now the most common
 no safety issues (e.g. can allow mobile vessels)
 can release to atmosphere
 takes longer and may lead to mechanical damage as tablets are tumbled for longer
 requires more efficient drying air plant
Advances in drying efficiency has allowed aqueous processes to be developed
even for moisture sensitive products

Film Coating - The Process

 The coater drum rotates and the baffles in the drum mix the tablets
 Warm air is drawn through the bed as it enters (inlet air) and exist (outlet air) the drum through perforations
Spraying on tabletsSolution Vessel
Coating PanBuffles
Solution Pump The distance from the spray guns to the tablet bed is measured and the spray adjusted to achieve and even (non overlapping) coverage across ~75% of the bed
 The coating suspension is pumped through the spray guns with compressed (atomising) air which forms a spray of fine droplets
 As the suspension droplets hit the tablet surface they should spread into a film before the solvent is rapidly removed by the throughput air
 The aim is to gradually build up the coat as the tablets pass beneath the spray guns


Common Components

Common Components of a Film Coat

•  Solvents
 water
 solvents
•  alcohols (e.g. ethanol, isopropanol)
•  esters (e.g. ethyl acetate, ethyl lactate)
•  chlorinated hydrocarbons (e.g. methylene chloride, 1:1:1 trichloroethane)
•  Polymers / Film Formers
 form a clear, non-tacky, mechanically strong film
 must be soluble in the chosen solvent and also allow release of drug in the body
-  must be compatible with the core contents most common example is Hydroxy propyl methyl cellulose (HPMC)

•  Plasticisers

-  modify the properties of the polymer to assist the coating process (e.g. by reducing brittleness of the coat)
-  need to be miscible with the polymer e.g. propylene glycol, polyethylene glycol (PEG)

•  Colourants

-  water insoluble pigments or water soluble dyes
     e.g. yellow or red iron oxide, aluminium lake dyes

•  Opacifiers

-  provide a “hiding” function preventing  the coat from being see through
-  used to mask core colour and / or provide light protection e.g. titanium dioxide



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