3. Types of Tablet Coating
• Three main types are in use:
o Film coating
o Sugar coating
o Compression coating
4. Types of Tablet Coating
Film coating involves the deposition, usually by a spraying
method, of a thin film of a polymer formulation surrounding a
tablet.
Sugar coating involves the successive application of sucrose-based
coating formulations, usually to tablet cores, in suitable
coating equipment.
Compression coating involves the compaction of granular
material around a preformed tablet core using specially
designed tableting equipment.
5. Film Coating
Film coating involves the deposition, usually by a spray
method, of a thin film of polymer surrounding the tablet core.
The coating liquid (solution or suspension) contains a polymer
in a suitable liquid medium together with other ingredients such
as pigments and plasticizers.
This solution is sprayed on to a rotating tablet bed. The drying
conditions facilitates the removal of the solvent leaving a thin
deposition of coating material around each tablet core.
6. Film Coating Vs Sugar Coating
Nearly all newly launched coated tablets are film coated rather than
sugar coated.
7. Film Coating
Materials used in film coating
Film former or polymer
Plasticizer
Colorants
Solvent
Opaquant-extenders
8. Ideal characteristics of film coating material
Solubility in solvent of choice for coating preparation.
Solubility required for the intended use e.g. free water
solubility, slow water solubility, pH-dependent solubility
(enteric coating).
Capacity to produce an elegant looking product.
Stability in the presence of heat, light, moisture, air and the
substrate being coated. The film properties should not change
with aging.
Essentially, no color, taste or odor.
9. Ideal characteristics of film coating material
Compatibility with common coating solution additives.
Nontoxicity with no pharmacologic activity and ease of
application to the particles or tablets.
Resistance to cracking and provision of adequate moisture,
light odor sublimation barrier when desired.
No bridging or filling of the debossed tablet surfaces by the
film former.
Ease of printing procedure on high speed equipment.
10. Types of Film Former or Polymer
Nonenteric Materials
Hydroxypropyl methyl cellulose (HPMC)
Methyl hydroxyethylcellulose
Ethylcellulose (EC)
Hydroxypropylcellulose (HPC)
Povidone
Sodium carboxymethylcellulose
11. Types of Film Former or Polymer
Enteric Materials
Cellulose acetate phthalate (CAP)
Hydroxypropyl methylcellulose phthalate (HPMCP)
Polyvinyl acetate phthalate (PVAP)
Acrylate polymer
12. Reasons for Enteric Coating
To protect acid labile drugs from the gastric fluid. e.g. Certain
antibiotics.
To prevent gastric distress or nausea due to irritation from a drug.
e.g sodium salicylate.
To deliver drugs intended for local action in the intestine. e.g.
intestinal antiseptic can be delivered to site of action in
concentrated form and bypass systemic absorption in the stomach.
To deliver drugs that are optimally absorbed in the small intestine
to their primary absorption site in their most concentrated form.
To provide delayed release component to repeat action tablets.
13. Characteristics of Ideal Enteric Coating Material
Resistance to gastric fluids.
Ready susceptibility to or permeability to intestinal fluids.
Compatibility with most coating solution components and the drug
substrates.
Stability alone and in coating solutions. The films should not change
on aging.
Formation of a continuous (uninterrupted) film.
Low cost.
Ease of application without specialized equipment.
Ability to be readily printed or to allow film to be applied to
debossed tablets.
