FILM COATING TECHNIQUES

AND PROBLEMS.

Submitted by:- Ajit kr. Jha

M.Pharm (Pharmaceutics)

Submitted To:-Dr. Majumdar D.

K.

Dept. of pharmaceutics

School of pharmacy,

Apeejay Stya University.

FILM COATING TECHNIQUES

AND

PROBLEMS

OVER VIEW :

1.INTRODUCTION 2.MECHNISM OF FILM

FORMATION 3. COATING PROCESS

AND METHOD

4. MATERIALS5. DEFECTS

COATING:

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

absorption .

INTRODUCTION:-

• A film is a thin polymer –based coat applied to a

solid dosage form such as a tablet granule or

particle.

• 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.

REASONS :-

Enhancing flavor

FILM COATING IS APPLIED FOLLOWING REASON:-

Modifying drug release

characteristics

Improving Product stability

Aqueous film coating :- [ solvent - water ]

Non aqueous film coating :- [ solvent –

organic]

1. FILM COATING IS PERFORMED AS TWO TYPES:-

FORMATION OF FILMS FROM AQUEOUS

POLYMERIC DISPERSIONS

This requires the coalescence of polymer particles into a continuous

film.

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.

Aqueous polymeric

must be processed at temperatures in excess of the glass-transition

temperature of the polymer.

MECHANISM OF FILM FORMATION

SUB TYPES:-

FILM COATING ARE SHOWES

VARIOUES SUBTYPES:-

• CONVENTIONAL FILM COATING.

• MODIFIED RELEASE FILM

COATING .

• SUSTAINED RELEASE FILM

COATING.

• 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

acceptence.

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.

COATING PROCESS

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

Coating equipment

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

high drying efficiency of aqueous film-

COATING LIQUID

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.

Accela Cota

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.

HI-COATER

DRIA COATER PAN

PROCESS PARAMETERS

• 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

coated tablets.

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 thinner films.

• 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 sticking.

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 coating.

• Excessive air temperature increases premature drying of the spray during application and subsequently decreases the coating efficiency.

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.

GENERAL PROCEDURE

The aqueous coating liquid is commonly applied by pneumatic (air) spray systems

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 tablets.

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 coating liquid.

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

moisture .

Non toxic.

Compatible with the common coating

solution ingredients.

Non enteric

materials-

Enteric materials-

Example:-Hydroxyl propyl

methyl cellulose,

sod.corboxy cellulose,

ethyl cellulose, acrylate

polymer EudragitE,

povidon, proply ethylene

glycol.

Example:- cellulose acetate

phthalate,acrylate

polymer,EudragitL,S

,Hydroxyl propyl methyl

cellulose phthalate,

polyvinyl acetate

FILM FORMER :-

Solvent

Alcohol

Ester

Ketons

Chlorinated hydrocarbons

Water

methanol,ethanol,isopropano

l,

Ethyl acetate ,ethyl

Acetone

Methylene choride

Plasticizers:-

Polyols

Organic esters

Oil-glycerides

Example:-

Glycerol poly, ethylene glycol(200-600grades)

Triacetin,diethyl phthalate, Dibutyl phthalate

Castoe oil, fractionated coconut oil.

EFFECTS OF PLASTICIZERS ON THE

PROPERTIES OF FILM COATINGS

P R O P E R T Y

Tensile strength

Elastic modulus

Film adhesion

Solution viscosity

Film permeability

E F F E C T O F I N C R E A S I N G P L A S T I C I Z E R C O N C E N T R AT I O N

Decreased.

Decreased.

May be increased, but results often variable.

Increased, and magnitude of effect dependent on

molecular weight of plasticizer.

Surfactant :-

Poly sorbets

Sorbitan ester

Colorants:-

Inorganic

Natural coloring

material

Example:-

Tweens

Spans

Example:-

FD&C, lakes & dyes,iron

oxide

Anthocyanin,caramel,Tur

mric ,carminic acid.

EFFECTS OF PIGMENTS ON THE

PROPERTIES OF FILM COATINGS

P R O P E R T Y

Tensile strength

Elastic modulus

Film adhesion

Solution viscosity

Film permeability

E F F E C T O F I N C R E A S I N G P I G M E N T C O N C E N T R AT I O NDecreases

Increases

Little effect.

Increases, but not substantially.

Decreases, unless critical pigment volume concentration is exceeded.

Opaquant extenders:-

Silicates

Carbonates

Sulfates

Oxides

Example:-

Titanium dioxide,talc.

Aluminium silicate

Mg carbonate

.

Calcium sulphate.

Mg oxides, hydroxides .

Miscellaneous

:-

Example:-

Antioxidants

flavours,

Antiadherants,

talc etc.

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 additives.

It is aqueous polymeric dispersion ethyl cellulose used for sustained release film coating.

HYDROXY PROPYL CELLULOSE:-

Used along with polymer to improve film characteristics .

PROVIDON:-

Available in different viscosity grades (K30,K60)

It has good solubility & provide hard clear glossy films.

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.

Low mol.wt.

PEG are hard & smooth tasteless.

ACRYLATE POLYMER :-

Marketed under trade mark .

EUDRAGIT*

EUDRAGIT:- It is cationic copolymer freely soluble

in GIT fluid up to PH5 .

These film are used for delayed action.

ENTERIC MATERIALS:-

Why enteric coating is done?

To protect acid labile drugs form gastric fluid E.g.:- Antibiotics.

To prevent gastric distress E.g.:- sodium silicate.

To provide a delayed release component.

CELLULOSE ACETATE PHTHALATE:-

Dissolve only above PH 5 CAP film are brittle (aqueous enteric coating) . Aquatic coating.

Acryl polymers:-

EUDRAGIT L - soluble in intestinal fluid at PH 6 .

HYDROXY PROPYL METHEYL CELLULOSE PHTHALATE :-

Marketed as HPMCP 5655,555.

Soluble at lower PH (5to 5.5).

Result in higher bioavailability.POLY ACETATE PHTHALATE :-

Has PH dependent solubility .SOLVENT :-

To dissolve or disperse the polymer.

Ideal characteristics of a solvent

Should have rapid drying rate .

Non toxic

Aqueous solvent based coating are much performed than non aqueous organic solvent based coating.

PLASTICIZERS:-

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 )

COLORANT S:-

May be soluble in solvent or

suspended as insoluble

powder.

F or light shade :- 0.01%

For dark shade :- >2.0%

MISCELLANEOUS COATING SOLUTION

COMPONENTS

To provide a dosage form with

a single characteristic, special materi

als may be incorporated into a

solution.

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

ilize immiscible or insoluble ingredien

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

composition.

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

alkylisothiazloinone, carbamates,

OPAQUANT EXTENDER:-

TO INCREASE FILM

COVERAGE .

TO MASK COLOR OF

TABLET CORE .

DEFECTS

/PROBLEMS

PROBLEM ENCOUTERED DURING FILM COATING

PICKING :-

A PICKING OF FILM MAY REMAIN

ADHERED TO PAN .

REASON:- LOCALIZED OVER

WETTING

REMEDY:- INCREASE DRYING AIR

TEMPERATURE .

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 COMES FORM

PICKING TABLET AHD STICKS ON THE TABLET

SURFACE.

TWINNING :- TABLET WITH FLAT EDGES/FACES

MAY BECOMES PERMANETLY.

MOTTLED COLOR :-

MIGRTION OF SOLUBLE DYE DURING

DRYING .

REMEDY :- USE OF LAKE DYES

ELIMINATION MIGRATION.

ORANGE PEEL EFFECT :-

INADEQUATE SPREADING OF COATING SOLUTION

BEFORE DRYING

REASON:- TO RAPID DRYING HIGH SOLUTION

VISCOSITY

RAMEDY:- THINING THE SOLUTION WITH

ADDITIONAL SOLVENT.

FILLING:-

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

FRIABILITY.

RAMEDY:- WORN PUNCHES .

CHIPPING :-

REASON:- THIS IS THE RESULT OF HIGH SPEED A FRIABLE TABLET .CORE A COATING SOLUTION THAT LACKS A GOOD PLASTICIZER.

FILM CRACKING:-

REASON :- IF INTERNAL STRESS IN FILM EXCEED

THE TENSILE STRENGTH OF FILM.

REMEDY:- TENSIL STRENGTH IS INCREASED BY

USING HIGH MOLEULAR WEIGHT POLYMER.

ROUGHESS:-

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

SURFACE..

REMEDY:- INCREASE &CHANGE PLASTICIZER.

BLOOMING /DULL FILM:-

COATING BECOMES DULL

REASON:- TOO HIGH PROCESSING TEMPERATURE

LOW MOL.WT OF PLASTICIZER.

REMEDY:- DECREASE PLASTICIZER

CONCENTRATION

& INCREASE MOL.WT OF PLASTICIZER.

OTHER PROBLEMS ENCOUNTERED

DURING FILM COATING:-

DUE TO EXCESSIVE MOISTURE

WITH IN THE TABLET.

WHICH PREVENTE COATING FROM

ADHERING.

REFERENCES:-

• Lachman/Lieberman’s “The Theory and Practice Of Industrial Pharmacy” Fourth Edition 2013, Edited by: Roop K Khar, SP Vyas, Farhan J Ahmad, Gaurav K Jain, CBS Publishers and Distributors Pvt Ltd, New Delhi.

• Doornbos C and Hann P. Optimization Techniques in Formulation and Processing. In Encyclopedia of Pharmaceutical Technology. Swarbrick J and Boylan JC, Eds., Vol. II, Marcel Dekker, New York. 199

• Modern Pharmaceutics Fourth Edition, Revised and Expanded, Edited By G.S.Banker & C.T.Rhodes, Marcel Dekker pg387-389.

• The Science & practice of Pharmacy, By Remington, Vol-01, 21st Edition, Lippincott Publication.