Tablet Coating Machine. Source: Rotronics UK
- Sugar-coated tablets are coated with a coloured or an uncoloured sugar layer. The coating is water soluble and quickly dissolves after swallowing. The sugar-coating protects the encapsulated drug from the environment and provides a barrier to objectionable tablet taste or odour.
- Film-coated tablets are compressed tablets coated with a thin layer of a polymer that forms a skin-like film. This is usually coloured and has the advantage over sugar coatings that it is more durable, less bulky, and works faster at the desired location in the gastrointestinal tract.
- Enteric-coated tablets have delayed release properties. They are designed to pass unchanged through the stomach to the intestines, where the tablets disintegrate and allow the drug to dissolve and start its effect. Enteric coatings are used when the drug substance itself would be destroyed by gastric acid or is irritating to the gastric mucosa.
How can accurate measurements help?
Environmental control is the practice of managing the temperature, humidity, air circulation, ventilation and air pressure of a given space. Within certain types of pharmaceutical manufacturing processes, precise environmental control can help limit inefficiencies and potential problems.
Pharmaceutical tablet coating is one such application. Inefficiencies during the coating process may result in contamination and tablet impurity in the form of tablet-to-tablet colour variation, surface pitting from over-wetting, twinning due to spray drying, cracking or peeling. Most of these problems can be overcome by better control of the environment within the process. Over-wetting, for example, occurs when the coating hits the still wet tablet surface and the surrounding air does not dry it quickly enough. Another example involves spray drying, when the coating hits the tablet surface after the moisture has been removed resulting in poor adhesion of the coating.