OVER VIEW :
2.MECHNISM OF FILM
3. COATING PROCESS
A coating is a covering that is applied to the
surface of an object.
It is the application of coating composition
on to the moving bed of tablets with
concurrent use of heated air to facilitate
evaporation of the solvent.
PURPOSE OF COATING:-
To mask unpleasant taste .
To control site of dissolution.
To protect components atmospheric
degradation such as oxidation
,absorption or evolution of moisture
,light etc .
To separate incompatible ingredient
and prevent their interaction.
To provide a controlled rate
• A film is a thin polymer –based coat applied to a
solid dosage form such as a tablet granule or
• The thickness of such a coating is usually
between ( 20 to 100 micrometer)
• Each and every tablet is passed through a
spray zone, where the adherent material is
sprayed and allowed to dry before the next
portion of coating and this process is repeated
number of times.
FILM COATING IS APPLIED FOLLOWING REASON:-
Aqueous film coating :- [ solvent - water ]
Non aqueous film coating :- [ solvent –
1. FILM COATING IS PERFORMED AS TWO TYPES:-
FORMATION OF FILMS FROM AQUEOUS
This requires the coalescence of polymer particles into a continuous
This process involves:
Rapid evaporation of water, causing the particles of dispersed
polymer to be brought into close contact with one polymer.
Development of pressures (associated with capillary forces
within the structure) that overcome repulsive forces between
particles and cause deformation of the polymer particles.
Gradual coalescence of the polymer particles as a result of
viscous flow and movement of polymer molecules across the
interfaces between particles.
must be processed at temperatures in excess of the glass-transition
temperature of the polymer.
FILM COATING ARE SHOWES
• CONVENTIONAL FILM COATING.
• MODIFIED RELEASE FILM
• SUSTAINED RELEASE FILM
• ENTERIC FILM COATING.
CONVENTIONAL FILM COATING:-
It has been applied to improve
product appearance ,improve
stability and ease of ingestion
without altering drug-release
characteristics form the dosage
form .conventional coating is the
area where aqueous technology
has gained the highest
MODIFIED RELEASE FILM COATING:-
Film coating techniques can be
effectively used either to
sustain the release (extended
release)0r delay the release
(enteric coating) of drug.
SUSTAINED RELEASE FILM COATING :
The film coating act a membrane that allows
infusion of GI fluid and the outward
diffusion of drug or the release process
may amplified by a coating that slowly
dissolves/ the subjected by enzymes.
The most common application of
sustained release coating is on micro
particles that are subsequently
encapsulated or tablet .
ENTERIC FILM COATING :-
The drug delivery system to
pass through the stomach
intact and dissolve upon
reaching the intestine.
Application of coating composition to a
moving bed of tablets with the concurrent
use of heated air of facilitate evaporation
of solvent .
Film-coating of tablets is a multivariate process,
with many different factors, such as coating
equipment, coating liquid, and process
parameters which affect the pharmaceutical
quality of the final product
Before few years different types of coating
pans are used for coating like conventional
coating pans, manesty accelacota, driam (
driacoater ), butterfly coater etc. Now a days
the side-vented, perforated pan-coater is the
most commonly used coating device of
tablets. In equipment spray nozzle, number
of spray nozzle, pan size, etc may also affect
the quality of final product. Its air flow
system through a perforated pan ensures
rapid and continuous drying conditions. The
low evaporation capacity of water requires
Coating liquid may affect the final
quality of the tablets. Different film
former have different chemical
nature and different characteristic.
Viscosity may affect the spreading
of coating liquid across surface of
substrate. Surface tension may
affect in wetting of surface. % Solid
content generally affect the tablet
surface and coating efficiency.
CONVENTIONAL COATING PANS :
It consists of a circular
metal pan placed
angularly on a stand
rotated on its horizontal
axis by motor .
Heat is directed in the
pan on the tablet bed
surface and is exhausted
by means of ducts .
PERFORATED PANS :
This is an angular pan
operating on a horizontal
axis. Drying air is directed
into the pan, through the
tablet bed, and exhausted
out the perforations in the
periphery of the pan.
This is similar to Accela Cota,
but only a portion of the pan
periphery has perforations.
Like the Accela Cota,
continuous venting of the
exhaust air from the
pan is still attained.
• Many quality aspects of the final coated product are
greatly influenced by the combined effect of process
parameter values used in aqueous film coating.
• Coating process parameters affect the spreading,
penetration and drying (i.e. evaporation of water) of the
coating liquid on the tablet surface and, subsequently,
the surface roughness and the residual moisture of the
SPRAYING AIR PRESSURE:
• The spraying air pressure disperse the coating liquid into
droplets and effects the droplet size distribution and
droplet spreading and penetration on the tablet surface.
• The formation of adequate and adhesive film coat, the
atomized droplets have to spread completely over the
surface of the tablet.
• Increasing the spraying air pressure decreases the surface
roughness of coated tablets and produces denser and
• If spraying air pressure is excessive the spray loss is
great. The formed droplets are very fine and could spray
dry before reaching the tablet bed, resulting in inadequate
droplet spreading and coalescence.
• Spraying air pressure is insufficient, the film thickness and
thickness variation greater possibly due to change in film
density and smaller spray loss.
FLOW RATE OF COATING SOLUTION
• Successful aqueous coating process, the flow rate
of the coating liquid is equal to the rate of water
evaporation from the coated tablet surface.
• Increasing the flow rate allows greater number of
droplets to be spread on to the tablet bed per time
and increases droplet size.
• The flow rate is important parameter since it
impacts the moisture content and the quality and
uniformity of the film.
• Low coating liquid flow rate causes incomplete
coalescence of polymer due to insufficient
wetting, which result in brittle films.
• High coating liquid flow rate may result in over
wetting of the tablet surface
and subsequent problems such as picking and
PAN AIR TEMPERATURE
• The pan air temperature effects drying
efficiency of the coating pan and the
uniformity of the coatings.
• High inlet air temperature increases drying
efficiency of aqueous film coating process and
decreases in water penetration into the tablet
• Excessive air temperature increases
premature drying of the spray during
application and subsequently decreases the
ROTATING SPEED OF THE PAN
• Increasing rotating speed of the pan improves mixing
of the tablets.
• The pan speed effects the time the tablet spend on the
spraying zone and subsequently, the homogenous
distribution of the coating solution on the surface
of each tablet throughout the batch.
• Increasing the pan speed decreases thickness variation
and improves the uniformity of the coating.
• Too rapid rotating speed of the pan will cause the tablet
to undergo excessive attrition and breakage.
FILM COATING METHODS :-
1.PAN POUR METHOD.
2.PAN SPRAY METHOD.
The aqueous coating liquid is commonly applied by pneumatic (air) spray
where the pressure of the spraying air disperses the coating liquid as
appropriately sized droplets
The coating of tablets in a coating pan involves spraying the coating
compositions through one or more spray guns onto rotating bed of
Coating process consists of the continuous application of coating liquids
to a small portion of the tablets in the pan.
The applied coating must dry before it touches the coating pan or
receives its next application.
To attain a continuous coating operation, the rate of water evaporation
from the coated tablets must equal the rate of water applied in the
The coating composition is also significant factor in establishing the
tablet coating rate. Coating compositions that are quite tacky during
the drying phase must be applied at a slower rate to avoid tablets
sticking to pan surface or other tablets.
MATERIAL USE OF FILM COATING
A ideal film coating material should have:-
Solubility in solvent (PH dependent
solubility , free water solubility)
Stable in the presence of heat light
Compatible with the common coating
EFFECTS OF PLASTICIZERS ON THE
PROPERTIES OF FILM COATINGS
EFFECT OF INCREASING
May be increased,
but results often
magnitude of effect
molecular weight of
EFFECTS OF PIGMENTS ON THE
PROPERTIES OF FILM COATINGS
P R O P E R T Y
Increases, but not substantially.
Decreases, unless critical pigment
volume concentration is
FILM FORMERS :-
Non enteric materials:
-HYDROXY PROPYL METHYL CELLULOSE:-
It is wide spread acceptance include:-
Solubility characteristics in GI fluid .
Non interference with tablet disintegration .
Flexibility absence of taste, odor.
Stability in presence of heat .
ETHYL CELLULOSE :-
Insoluble in GI fluid.
Hence used along with water soluble
It is aqueous polymeric dispersion ethyl
HYDROXY PROPYL CELLULOSE:-
Used along with polymer to improve film
Available in different viscosity grades
It has good solubility & provide hard clear
SODIUM METHYL CELLULOSE:-
It is easily dispersible in water to form
colloidal dispersion in most organic
solvent hence not preferred.
Film prepared are brittle.
POLY ETHYLENE GLYCOL:-
Available in low & high molecular weights
Film prepared with high mol .wt combination PEG
with cellulose acetate phthalate produce films
soluble in GI fluid.
PEG are hard & smooth tasteless.
ACRYLATE POLYMER :-
Marketed under trade mark .
EUDRAGIT:- It is cationic copolymer freely soluble
in GIT fluid up to PH5 .
These film are used for delayed action.
Why enteric coating is done?
To protect acid labile drugs form gastric
fluid E.g.:- Antibiotics.
To prevent gastric distress E.g.:- sodium
To provide a delayed release component.
CELLULOSE ACETATE PHTHALATE:-
Dissolve only above PH 5 CAP film are
brittle (aqueous enteric coating) . Aquatic
EUDRAGIT L - soluble in intestinal fluid at
HYDROXY PROPYL METHEYL CELLULOSE
Marketed as HPMCP 5655,555.
Soluble at lower PH (5to 5.5).
Result in higher bioavailability.
POLY ACETATE PHTHALATE :-
Has PH dependent solubility .
To dissolve or disperse the polymer.
Ideal characteristics of a solvent
Should have rapid drying rate .
Aqueous solvent based coating are much
performed than non aqueous organic
solvent based coating.
Make polymers of & enhance flexibility .
Modify physical &*mechanical properties of film.
Reduce glass transition temperature of
amorphous polymer & impart flexibility.
Recommended level of plasticizer rang 1-50%
weight of film former.
The quality of polymer film is modified by :-
Internal plasticization - (Chemical change
are made with in structure of polymers )
External plasticization - ( By using
additives plasticizers )
May be soluble in solvent or
suspended as insoluble
F or light shade :- 0.01%
For dark shade :- >2.0%
MISCELLANEOUS COATING SOLUTION
To provide a dosage form with
a single characteristic, special materi
als may be incorporated into a
Flavors and sweeteners are added to
mask unpleasant odors or to develop
the desired taste. For example,
aspartame, various fruit spirits (organic
solvent), water soluble pineapple flavor
(aqueous solvent) etc.
Surfactants are supplementary to solub
Antioxidants are incorporated
to stabilize a dye system to
oxidation and color change. For
example oximes, phenols etc.
Antimicrobials are added to put off
microbial growth in the coating
Some aqueous cellulosic coating sol
ution are mainly prone to microbial
growth, and long-lasting storage of the
coating composition should be
avoided. For example
TO INCREASE FILM
TO MASK COLOR OF
TABLET CORE .
A PICKING OF FILM MAY REMAIN
ADHERED TO PAN .
REASON:- LOCALIZED OVER
REMEDY:- INCREASE DRYING AIR
REDUTION IN LIQUID
APPLICATION RATE .
PICKING DOES NOT OCCUR ALONE MUST HAVE
ANOTHER TABLET TO BE STUCK WITH WHICH
CALLED STICKING :-
. STICKING IS THE DEFECT THAT THE BROKEN FILM COME
PICKING TABLET AHD STICKS ON THE TABLET
TWINNING :- TABLET WITH FLAT EDGES/FACES
MOTTLED COLOR :-
MIGRTION OF SOLUBLE DYE DURING
REMEDY :- USE OF LAKE DYES
ORANGE PEEL EFFECT :-
INADEQUATE SPREADING OF COATING SOLUTION
REASON:- TO RAPID DRYING HIGH SOLUTION
RAMEDY:- THINING THE SOLUTION WITH
CAUSED BY APPLYING TO MUCH SOLUTION
,RESULTING IN A THICK FILM FILLS & NARROWS
THE MONOGRAM OR IS BISECT .
EDGE WEAR :-
REASON :- TABLET CORE HAVING HIGH
RAMEDY:- WORN PUNCHES .
REASON:- THIS IS THE RESULT OF HIGH
SPEED A FRIABLE TABLET .CORE A
COATING SOLUTION THAT LACKS A GOOD
REASON :- IF INTERNAL STRESS IN FILM EXCEED
THE TENSILE STRENGTH OF FILM.
REMEDY:- TENSIL STRENGTH IS INCREASED BY
USING HIGH MOLEULAR WEIGHT
REASON:- WHEN COATING IS APPLIED BY SPRAY SOME
OF THE DROP DRY BEFORE REACHING THE
TABLET BED .
REMEDY:- MOVING THE NOZZLE CLOSE TO TABLET BED.
BRIDGING:- DURING DRY ING FILM MAY SHRINK & CORNER
OF BISECT ,RESULTING IN BRIDIENG OF
REMEDY:- INCREASE &CHANGE PLASTICIZER.
BLOOMING /DULL FILM:-
COATING BECOMES DULL
REASON:- TOO HIGH PROCESSING TEMPERATURE
LOW MOL.WT OF PLASTICIZER.
REMEDY:- DECREASE PLASTICIZER
& INCREASE MOL.WT OF PLASTICIZER.
OTHER PROBLEMS ENCOUNTERED
DURING FILM COATING:-
DUE TO EXCESSIVE MOISTURE
WITH IN THE TABLET.
WHICH PREVENTE COATING FROM
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Roop K Khar, SP Vyas, Farhan J Ahmad, Gaurav K Jain,
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• Modern Pharmaceutics Fourth Edition, Revised and
Expanded, Edited By G.S.Banker & C.T.Rhodes, Marcel
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