Coating of Tablets
Tablet coating is the application of coating material to the exterior of a tablet which is an additional step in manufacturing process.
As per IP (Indian Pharmacopoeia), tablet can be coated with mixture of various substances such as resins, gums, inactive and insoluble fillers, sugars, waxes etc.
The decision to coat tablets is usually based on the following objectives:
- To mask the bitter taste
- To mask the unpleasant odor
- To protect the drug from surroundings
- To increase the stability
- To promote easy handling and ease of ingesting by patients
- To provide mechanical protection from breakage
- To avoid light incompatibility
- To impart protection from environmental oxidation
- To modify the drug release profile
- To identify the product
In the coating process, the tablets rolls in a coating pan or cascade in the air stream of an air suspension as the coating (compression) composition is applied.
To tolerate the intense attrition of tablets striking other tablets or walls of coating equipment, the tablets must be resistant to abrasion and chipping.
Tablet surfaces that are brittle, that soften in the presence of heat or that are affected by the coating composition tend to become rough in the early phase of the coating process and are unacceptable for the film coatings.
When a coating composition is applied to a batch of tablets in a coating pan, the tablet surface becomes covered with a tacky polymeric film. Before the tablet surface dries the applied coating changes from a sticky liquid to a tacky semi-solid and eventually to a non-tacky dry surface.
The ideal shape of tablet for coating is a sphere, which allows tablets to roll freely in a coating pan with minimal tablet to tablet contact. It also helps in increased packing speed and also in product identification
The worst shape is a square flat-faced tablets in which case coating material would collect between the surface to glue them together like a stack of domino’s or poker chips. For this reason, coated tablets have rounded surfaces, the more convex the surface is, the fewer difficulties will be encountered with the tablet agglomeration.
Coating for Marketing
- To allow product to make stand out from the competition
- To impart color, taste and tablet shape for branding and trademark
Coating for Product Stability
- To prevent product sunlight degradation
- To prevent absorption of moisture by the product
- To prevent environmental oxidation of product
Coating for Release
The release of drug from tablets is also governed by tablets coating
- No functional coats applied. Drug is going to be released immediately after administration of tablets.
- To provide release of drug at various G1 sites depending on PH.
- To change the rate of release of active drug. For example, Control release of active drug over 24 hrs.
Coating for Consumers
Patient compliance is affected by products appearance
- To provide ease of use tablets are usually coated
- To identify the product, however tablets coating doesn’t play a vital role in identification because almost all tablets of all companies are processed with coating after manufacturing
- To improve efficacy of tablets
- To mask the taste and odor of tablets
Types of Coating of Tablets
There are usually five (5) major types of coating processes of tablets. They include
- Sugar Coating
- Film Coating
- Enteric Coating
- Controlled Release Coating
- Specialized Coating
Each will be discussed in detail in our later posts…