Learn about film coating process, difference between Aqueous and Solvent (non-aqueous) film coating and parameters.
Film coating Involves spraying a solution of polymer + pigments + plasticizers on to a rotated, mixed tablet bed forms a thin, uniform film on tablet surface.
Tablet film coating is performed two types, one is aqueous film coating (generally water is used as a solvent) and non-aqueous film coating (generally organic solvents are used.) Some problems are associated with the non-aqueous film coating like safety of employees (as most of the solvents dangerous smells, and they are not good to breathe) atmosphere pollution etc. But key problem is with the approval of the regulatory authority. High quality aqueous film coating must be smooth, uniform and adhere satisfactorily to the tablet surface and ensure chemical stability of a drug.
Minimal weight gain (2-3% as opposed to 60-80% for sugar coating)
Single stage process an so generally quicker
Coat is less likely affect disintegration
Expensive equipment & plant requires large space
Easy to automate (less reliance on skilled operator / easier to meet GMP requirements of SOPs, validation etc.)
High installation & energy costs.
Aqueous vs Solvent Film Coating
Aqueous Film Coating
Aqueous based process are now the most common
-No safety issues (e.g. can be allow mobile vessels)
-can release to atmosphere
Take longer and may lead to mechanical damages as tablets are tumbled for longer
Requires more efficient drying air plant
Advance in drying efficiency has allowed aqueous processes to be developed
Even for moisture sensitive products
Solvent Film Coating
-Solvent based coating solution / suspension (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
Common component of film coating
Solvents – Alcohols (e.g. ethanol, isopropanol)