A film coating is a thin polymer-based coat applied to solid dosage forms in the pharmaceuticals and complementary medicines industry.
The coating is applied through a spraying process after compression using specialised coating equipment.
The coating can be clear or a vast range of coloured film which can be made in-house or bought as a premix through reputable brands available on the market.
Basic film coating solutions contain water soluble materials that dissolve completely in the gastrointestinal tract and do not modify the drug release characteristics of the dosage form. These are made in aqueous film coating suspensions and contain the following ingredients:
- Polymers – such as Hypromellose or polyvinyl alcohol which provide the tensile strength of the coat.
- Plasticizers – such as polyethelyne glycol (PEG)/macrogol which provide the capacity to alter the physical properties of the polymer to make it softer and more pliable and also improve adhesion to the tablet surface.
- Colourants – such as titanium dioxide, iron oxides, aluminium lakes of dyes, natural materials to provide the colour of the coating.
The final quality of the coated product is influenced by the combination of processing parameters during the film coating process. Common coating defects include: rough/orange peel appearance, picking/sticking, peeling, mottling, logo bridging, erosion and colour variation and many of these issues can be addressed by the modification of critical process parameters.
The following are some of the parameters should be considered when establishing the coating process for any particular product:
- Physical properties of the tablet core
- Spray solution preparation method
- Atomizing air pressure
- Suspension flow Rate
- Spray distance
- Pan Air Temperature
- Pan Speed
Refer to Tablet Coating Basics – Part 2 next month for more detail on some of the main critical process parameters.
Why Coat Tablets:
- Physical protection against chipping/ erosion
- Cosmetic considerations to add colour or gloss
- Brand recognition and appeal
- Product stability – light and moisture protection
- Making a tablet easier to swallow
- Mask taste/smell of active ingredients
- Modify drug release
January 2019
Vitex Pharmaceuticals Pty Ltd
