1. COATING OF TABLET
BY,
MD. SHAFIQUL ISLAM
(Compliance officer)
ACI LTD.

2. DEFINITION
Tablet coating is the application of a coating
material to the exterior of a tablet with the
intention of conferring benefits and properties
the dosage form over the uncoated variety.

3. PURPOSE OF TABLET COATING
 Cover the unpleasant taste, odor and color.
 Physical and chemical protection in medicine from
environment (light, moisture, and air).
 Control of drug release as in enteric coating or
sustained release or more usually to coated multi
particulates.
 To protect drug from the gastric environment of the
stomach with an acid-resistant enteric coating.
 Improve the appearance of tablets.
 Assist and facilitate the identification of drug.
 Easing the process of blistering.

4. PRIMARY COMPONENTS
INVOLVED IN TABLET COATING
 There are three primary components involved in
tablet coating:
 1. Tablet properties.
 2. Coating process. → Coating equipment. →
Parameters of coating process. → Facility and
ancillary equipment. → Automation in coating
process.
 3. Coating composition.

5. TYPES OF TABLET COATING
Various kinds of tablet coating
 Sugar coating
 Film coating
 Enteric coating
 Press coating

6. SUGER COATING
Sugar coating is a multistage process and
can be divided into the following steps:
 Sealing of the tablet cores
 Sub coating
 Smoothing
 Coloring
 Polishing
Sealing/Water proofing: Provides a moisture
barrier and harden the tablet surface.
 e.g. :Shellac, Zine, Cellulose acetate phthalate
(CAP), Polyvinylacetate
phthalate, Hyroxylpropylcellulose, Hyroxypropylmet
hylcellulose etc

7. SUGER COATING
Subcoating: Causes a rapid buildup to round off the tablet edges.
 Generally two methods are used for subcoating:
1)The application of gum based solution followed by dusting with powder
and then drying. This routine is repeated until the desired shape is
achieved.
 2)The application of a suspension of dry powder in gum/sucrose solution
followed by drying.

 III. Grossing/Smoothing: It is specifically for smoothing and filing the
irregularity on the surface generated during subcoating. It also increases
the tablet size to a predetermined dimension.
 IV. Colouring: Gives the tablet its colour and finished size.
 V. Polishing: Produces the characteristics gloss. Polishing is achieved by
applying the mixture of waxes like beeswax, carnubawax, candelila wax or
hard paraffin wax to tablets in polishing pan.

8. FILM COATING
Involves spraying a solution of polymer + pigments
+ plasticizers on to a rotated, mixed tablet bed forms
a thin, uniform film on tablet surface.
Coating suspension formulation:
 Typically this comprises:
 Polymer
 Plasticizer
 Colourants
 Solvent.

9. IDEAL CHARACTERISTICS A FLIM
COATING POLYMER
 Solubility: For conventional film coating the polymer
should have good solubility in aqueous fluids to facilitate the
dissolution of the active ingredient from the finished dosage
form. However, where a modified-release action is required
then a polymer system of low water solubility or permeability
will be chosen.
 Viscosity: Polymers should have a low viscosity for a given
concentration. This will permit the easy, trouble- free
spraying of their solutions in industrial film coating
equipment.
 Permeability: Film coating can be used to optimize the
shelf-life of a tablet preparation, as some polymers are
efficient barriers against the permeability of water vapour or
other atmospheric gases. These properties vary widely
between the individual polymers.

10. PLISTICIZER
 Plasticizers are generally added to film coating
formulations to modify the physical properties of the
polymer to make it more usable. One important property
is their ability to decrease film brittleness.
Examples of plasticizers are:
 Polyols, such as polyethylene glycol 400
 Organic esters, such as diethyl phthalate
 Oils/glycerides, such as fractionated coconut oil. In
general, only water-miscible plasticizers can be used
for aqueous-based spray systems.

11. COLOURANTS
 Any permitted colourants in a film coat formula are
invariably water-insoluble colours (pigments).
Pigments have certain advantages over water-soluble
colours: they tend to be more chemically stable
towards light, provide better opacity and covering
power, and optimize the impermeability of a given film
to water vapour.
Examples of colourants are:
• Iron oxide pigments
• Titanium dioxide
• Aluminium Lakes.

12. SOLVENTS
 Modern techniques now rely on water as a polymer solvent
because of the significant drawbacks that readily became
apparent with the use of organic solvents.
 The disadvantages of organic solvents for the process:
 1. Environmental: the venting of untreated organic solvent
vapor into the atmosphere is
ecologically unacceptable, and efficient solvent vapor
removal from gaseous effluent is expensive.
2. Safety: organic solvents provide explosion, fire and toxic
hazards to plant operators.
3. Financial: the use of organic solvents necessitates the
building of flame- and explosion-proof facilities. Ingredient
cost is also comparatively high, and the associated costs of
storage and quality control must also be taken in to
consideration.

13. ENTERIC COATED TABLET
 This technique is used to protect the tablet core from
disintegration in the acid environment of the stomach
for one or more of the following reasons:
 Prevention of acid attack on active constituents
unstable at low pH.
 To protect the stomach from the irritant effect of certain
drugs.
 To facilitate absorption of a drug that is preferentially
absorbed distal to the stomach.
 Polymer are insoluble in aqueous media at low pH, but
as the pH rises they experience a sharp, well defined
increase in solubility at a specific pH.

14. PRESS COATING
 Use of compression to form coat around a pre-formed core.
Fig: Press coated tablet
 Used mainly to separate chemically incompatible materials.
 Also dual release patterns possible
 Compression coating is a dry process.

15. MAJOR DIFFERENCES BETWEEN SUGER
& FILM COATING
FEATURES FILM COATING SUGAR COATING
Appearance Retain contour of original Rounded with high degree
core. Usually not as shiny as of polish
sugar coat type
Weight increase 2-3% 30-50%
because of coating
material
Logo or ‘break lines’ Possible Not Possible
Process stages Usually single stage Multistage process
Typical batch coating 1.5 to 2.0 Hours Eight hours but easily
time longer
Functional coatings Easily adaptable for Not usually possible apart
controlled release from enteric coating

16. COATING MACHINE
Fig : Coating Machine Fig: Typical Spry Gun
1=Inlet air, 2=Inlet air filter and air heater
3=Coating pan, 4=Compressed air,
5=Pneumatic spray 6=Outlet air
7=Container with pneumatic stirrer 8=Peristaltic pump
(Control pressure 5-6 bar, Atomizing air pressure 1-2 bar)

17. CHECKPOINTS OF TABLET
COATING
 Check that coating Suite are properly cleaned & dry.
 All correct documents are available
 Check for QC approved (Green) status label and the re-
testing date on the container.
 Check that all balance are calibrated.
 Check that correct dispensed RM is available
 Check the gross weight of the container to be dispensed
and the quantity matches with the labeled quantity.
 Monitor that during material handling the operator should
wear mask and gloves.
 Monitor every step of coating.
 Any deviation during coating process should be
immediately take initiative to resolve.

18. CHECKPOINTS OF TABLET
COATING
IMPORTANT PROCESSING PARAMETERS
 Inlet & Outlet of bed temperatures.
 Relative humidity.
 Atomization air pressure.
 Pan speed.
 Liquid spray rate.
 Gun nozzles check.
 Spray gun calibration.
 Solid content of coating solution.
 Nozzle-to-bed distance.
 Droplet size.
 Drying time

19. CHECKPOINTS OF COATING
 Check the appearance of coated tablets paying
attention to the
 Color variation
 Sticking
 Twinning
 Cracking
 Capping
 Lamination
 Broken tablet
 Orange peel
 Fibers
 Black spot
 Oil spot, etc.

20. PROBLEM OF COATED TABLET
 Sticking and picking
 Roughness
 Orange peel
 Color variation
 Cracking
 Twinning
 Capping
 Lamination
 Blistering
 Catering

21. PROBLEM OF COATED TABLET
Sticking and picking: Over wetting or excessive film
thickness causes tablets to stick each other or to the
coating pan. - On drying at the point of contact, a
piece of film may remain adhere to pan or tablet. -
Giving “picked” appearances to the tablet surface. -
Resulting in a small exposed area of the core.
Remedies:
 Reduction in liquid application rate.
 Increase in drying air temperature and air volume.

22. PROBLEM OF COATED TABLET
 Roughness: A rough or gritty surface observed when the coating is
applied by spray.
 Causes : Some of the droplets may dry too rapidly before reaching the
tablet bed and deposits on tablet surface. On tablet surface spray- dried
particles of finely divided droplets of coating solution. Surface roughness
also increases with pigment concentration and polymer concentration in
the coating solution.
 Remedies :
• Moving the nozzle closer to the tablet bed.
• Reducing the degree of atomization can decrease the roughness due to
spray drying .

23. PROBLEM OF COATED TABLET
 Orange Peel: Inadequate spreading of coating solution before
drying causes a bumpy or Orange –peel effects on the coating.
 Fig: Orange Peel
 Causes :Indicates that spresding is impaired by rapid rate of
drying or by high solution viscosity.
 Remedies : Thinning of coating solution with additional solvents
may correct this problem.

24. PROBLEM OF COATED TABLET
 Colour variation: Colour variation Problem caused by process
conditions or the formulation Improper mixing, uneven spray
pattern and insufficient coating may results in colour variation.
The migration of soluble dyes, plasticizer and other additives
give the coating a mottled or spotted appearance.
Fig: Colour variation tablet
 Remedies : Proper mixing of coating solution
• Spray uniformly
• Use of lake dyes eliminates dye migration.
• A reformulation with different plasticizer and additives is the
best way to solve film instability.

25. PROBLEM OF COATED TABLET
Cracking : Cracking occurs if internal stresses in the
film exceed the tensile strength of the film. The tensile
strength of the film can be increased by using higher
molecular –weight polymers or polymer blends.
 Remedies: Adjusting the plasticizer types and
concentration can minimize internal stresses Also
adjusting the pigment types and concentration can
minimize internal stresses
Blistering : Evaporation of solvents from the core in the
oven. And effect of high temperature on the
strength, elasticity and adhesion of the film may results
in blistering.
 Remedies :Controlled drying conditions.

26. PROBLEM OF COATED TABLET
Twinning: Two or more tablets are stick together.
 Unbalancing the pan speed.
 Hi spray rate.
Fig: Twinning effect
Remedies: This problem can be solve by balancing the pan speed and
spray rate

27. IDEAL CHARACTERISTICS OF
COATED TABLETS
 Film-coated tablets must comply with the uniformity of mass
test unless otherwise justified and authorized
 Film-coated tablets comply with the disintegration test.
 Film-coated tablets should display
 An even coverage of film and colour.
 No abiasion of tablet edges or crowns.
 Logos and break lines should be distinct and not filled in.
 The tablet must also be within specifications and any
relevant compendial requirements.
 Tablets must comply with finished product specifications and
any appropriate compendial requirements.
 Sugar-coated tablets should ideally be of a perfectly smooth
rounded contour with even colour coverage. Most
manufacturers take advantage of the aethetic appeal of a
sugar-coated tablet and polish to a high gloss.
 Any printing should be distinct, with no smudging or broken
print.

28. Coated tablets Store
 Store the coated tablets in plastic drum with double
polythene bags with silica gel between the bags &
close the poly bags and fix-up lids of the plastic
drum properly. Label the plastic drum with Product
name, Batch No, Gross tare & Net weight ,Drum
number & signature of the authorized person.

29. Coating may be something of an art, but we’ll get
better results when we apply a little science to it.
THANKS TO ALL