The application of coating to tablets, which is an additional step in the
manufacturing process, increases the cost of the product; therefore, the
decision to coat a tablet is usually based on one or more of the following
objectives
I. To mask of the unpleasant odor or color of the drug
2. To provide physical or chemical protection for the drug
3. To control the release of the drug from the tablet
4. To protect the drug from the
gastric environment of the stomach with an acid resistance enteric coating
5. To provide sequential drug release
6. To improve the pharmaceutical elegance the use of special color and
contrasting printing
Tablet coating process
In most cases, the coating process is the last critical step in the
tablet production cycle. The successful application of the coating solution
formula to a tablet provides the visual characteristics for the product. This
type of process chosen depends on the type of coating that is to be applied,
durability of the core and the economics of the process. Because of the
ever-increasing cost of energy and labor, the cost of the organic solvents and
the associated environmental constrains, the economics of the process is
receiving greater emphasis. There are three coating processes in
pharmaceuticals, these areas-
• Film coating
• Enteric coating
• Sugar coating
Criteria of
film coating material
An ideal film coating material should have the following criteria
I. Solubility in solvent of
choice for coating preparation.
2. Capacity to produce an
elegant looking product.
3. Stability in the
presence of heat, light, moisture, air and the substrate being coated. The film
properties should not change with aging.
4. Essentially no taste,
color or odor
Example of coating materials are-
• Hydroxyl
propylmethylcellulose US
• Providon USP (1
-vinyl-2-pyrolidinone group)
Criteria of enteric coating
material
An ideal enteric coating material should have the following criteria
a. Resistant to gastric fluid
b. Ready susceptibility or permeability to intestinal fluid
c. Compatibility with the drug substance
d. Stability in coating solution
e. Fonnation of a continuous film
f. Non toxicity and low costing.
Example: Sodiumsalicylate.
